Guidelines for Smartphone Usage in Telemedical Photography

Guidelines for smartphone usage in telemedical photography

ANNA HAGMAN SANDER RIEDBERG

Bachelor of Science Thesis in Medical Engineering Stockholm 2014 i

This bachelor thesis project was performed in collaboration with Supervisor at STH: Medical Photographer Staffan Larsson

Guidelines for smartphone usage in telemedical photography

Riktlinjer för användning av smartphones inom telemedicinsk fotografering

ANNA HAGMAN SANDER RIEDBERG

Bachelor of Science Thesis in Medical Engineering Basic level (first cycle), 15 credits Supervisor at KTH: Erik Widman Examiner: Lars Gösta Hellström School of Technology and Health TRITA-STH. EX 2014:52

Royal Institute of Technology KTH STH SE-141 86 Flemingsberg, Sweden http://www.kth.se/sth

Preface

We would like to thank a number of people without whom this thesis would not have been possible to write. Thank you Linnea and Louise for inspiration, and Simon for your kindness. Thank you Staﬀan Larsson for all the energy and the supervision. We would also like to thank Erik Widman and Lars-Gösta Hellström for input and help throughout the thesis.

Anna Hagman and Sander Riedberg

School of Technology and Health, Royal Institute of Technology

2014-05-23

Abstract

The wide usage of smartphones makes them an interesting and potential medical device. Given that smartphone cameras have a suﬃciently high quality - some of the medical photography done at health care facilities could be done telemedically and by non-medically educated persons. Therefore a research of the quality of the photos taken with smartphone cameras has been done. This thesis presents guidelines regarding how inexperienced persons could take high qualitative medical photos with a smartphone.

This thesis includes a review of current guidelines within medical photography. A comparison between two popular smartphones and a professional medical camera has been done - where possibilities and limitations in smartphone cameras have been identiﬁed. In order to evaluate the sharpness and the color temperature representation in the photos taken with smartphones, an experiment with realistic lighting and easy accessible color-calibration cards has been done. The execution and the achieved result have formed the basis of the proposed guidelines.

The result shows that smartphone cameras are of high quality and thereby could be used as a complement to advanced medical camera equipment. With the help of the proposed guidelines inexperienced persons could acquire suﬃciently good medical photos, in order to be used as diagnostic material. This thesis provides a foundation for further research and implementation within the area, with the purpose of becoming an important part of the eﬃciency improvement within the telemedical health care.

Keywords: Medical technology, telemedicine, medical photography, guidelines, smartphone, smartphone camera.

vii

Sammanfattning

Dagens breda användande av smartphones gör dem till intressanta och potentiella medicinska verktyg. Givet att dess kameror håller en tillräckligt hög kvalitet skulle en del av den medicinska fotografering som görs på vårdinrättningar kunna göras telemedicinskt och av icke-medicinskt utbildade personer istället. Därför har en undersökning av kvaliteten på bilder tagna med smartphone-kameror gjorts. Detta examensarbete presenterar riktlinjer för hur oerfarna personer skall kunna ta högkvalitativa medicinska fotograﬁer med en smartphone.

I detta arbete har nuvarande riktlinjer inom medicinsk fotografering undersökts. En jämförelse mellan två populära smartphones och en avancerad medicinsk kamera har gjorts - där möjligheter och begränsningar hos smartphones har identiﬁerats. För att utvärdera skärpan och färgtemper- aturen i fotograﬁer tagna med smartphones, har ett experiment med realistiska ljussättningar och lättillgängliga kalibreringskort gjorts. Genomförandet och resultatet har utgjort grunden för de föreslagna riktlinjerna.

Resultatet visar att smartphone-kameror är av hög kvalitet, och därmed kan användas som ett komplement till avancerad medicinsk kamerautrustning. Med hjälp av de föreslagna riktlinjerna skulle oerfarna personer kunna ta tillräckligt bra medicinska fotograﬁer, för att de skall kunna användas som diagnostiskt underlag. Detta utgör en grund för fortsatt forskning och im- plementering inom ämnet, med syftet att kunna bli en betydande del av eﬀektiviseringen inom telemedicin.

Nyckelord: Medicinsk teknik, telemedicin, medicinsk fotografering, riktlinjer, smartphone, smartphone-kamera.

ix Table of Contents

1 Introduction 1 1.1 Background ...... 1 1.2 Objective ...... 2 1.3 Limitations ...... 2

2 Methods and material 3 2.1 Information retrieval ...... 3 2.2 Photo session ...... 3 2.2.1 Material ...... 4 2.2.2 Implementation ...... 4 2.2.3 Image processing ...... 5

3 Technical review 7 3.1 Camera hardware ...... 7 3.2 Exposure ...... 8 3.3 Color temperature ...... 8 3.4 Lighting ...... 9 3.5 Comparison ...... 9

4 Result 11 4.1 Photos ...... 11 4.2 Guidelines ...... 13

5 Discussion 15 5.1 Evaluation of the result ...... 15 5.2 Evaluation of the method ...... 16 5.3 Technical aspects ...... 17 5.4 Future possibilities ...... 17

6 Conclusion 19

7 References 21

Appendix 1 Photos ...... 1 Measurements ...... 8

x Chapter 1

Introduction

1.1 Background

During the past few years, the usage of smartphones in the medical sector has increased sig- niﬁcantly. The advanced technology of smartphones has enabled the possibility to complement some of the care given at health care facilities to be done remotely instead, i.e. telemedically. The usage of smartphones as a telemedical device is foreseen to give both economical and time beneﬁts - as well as facilitate the increasing workload at health care facilities [1, 2]. Stockholm County Council states in their future vision report [3] that the telemedical area is planned to increase in importance in the near future.

There are several smartphone applications on the market that offer different telemedical functions, including medical photography and image diagnostics. An example is teledermatology, which is defined as a way to transfer digital information concerning skin diseases [4–6]. Some other are fundus photography [7] and teleotolaryngology - a digital diagnosis of ear, throat and nose diseases [8]. Common for all the three different examination methods is that they are effec- tive, accurate and simple to use.

The professional medical camera equipment that is currently used in medical photography, requires an experienced and medically skilled user [9]. Furthermore, this equipment is expensive and therefore inaccessible for common people. Consequently, most of the medical photography sessions are done at hospitals or telemedically by medical professionals for communication and counseling purposes [10].

Many organizations and medical scientists have developed guidelines and instructions, as well as proposed standardized procedures for medical photography [11–14]. There are also literature that explain the image procedure within diﬀerent areas of medical photography [15–17]. Institute of Medical Illustrators (2013) has published a draft of guidelines for mobile phone photography. Thus, there is much information about how to take qualitative medical photos. As mentioned before there are also several smartphone applications which, with or without a need of external attachments, provide medical diagnostic services. Nonetheless a lack of information and instructions regarding how the smartphone can be used as a medical device, and by inexperienced persons, in the telemedical area is identiﬁed.

1 Chapter 1 Introduction

1.2 Objective

This project aims to examine how inexperienced photographers can take medically usable photos in order to facilitate telemedical diagnostics, by using a smartphone and with help of guidelines. The purpose of the thesis is to answer:

• What technical requirements should be met for the smartphone camera to be used in medical photography? • What properties are essential in medical photos in order to be used as medical diagnostic material? • What guidelines should be given to an inexperienced person in order to take medically usable photos with a smartphone?

This thesis is expected to be a foundation in the development and eﬃciency improvement within medical photography.

1.3 Limitations

The following limitations have been applied:

• The guidelines only include how to take photos of exterior body parts. • The guidelines are adapted to smartphones and not ordinary mobile phones. • The thesis does not include information about data storage.

2 Chapter 2

Methods and material

2.1 Information retrieval

In order to determine which properties that make a photo medically usable, literature studies regarding the medical requirements and current guidelines of medical photography have been done. Scientiﬁc articles have been found in the KTH database Primo as well as in PubMed. Photo books and medical photography guidelines have been provided by the supervisor Staﬀan Larsson.

Properties of smartphones and professional medical camera equipment have been found in technical speciﬁcations. The technical functions and restrictions within the smartphone cameras have been analyzed and compared to the professional medical camera. This information was sum- marized and presented in the following technical review chapter. The technical review, as well as the experiences and results gained from the photo session, founded a base for the developed guidelines.

2.2 Photo session

A photo session was conducted in order to evaluate photos taken with two diﬀerent smartphone cameras, and compare them to photos taken with an advanced camera. The advanced camera was a model used by many professional photographers, including medical photographers. This due to its high resolution, speed and ability to be manually adjusted. The smartphones used were easy accessible models. They also fulﬁlled the technical requirements for smartphone cameras found during the information retrieval.

The experiment was aimed to assess the smartphone cameras capability to generate images with correct color temperature and good sharpness. It was designed to simulate a realistic and everyday situation. Furthermore, it was aimed to be a foundation for the guidelines. The motif chosen was a nevus, since it is a very common motif within telemedical photography [16]. It also provided a basis for assessment of both sharpness and color representation.

3 Chapter 2 Methods and material

2.2.1 Material

• DSLR Camera; Nikon D700 • Minolta Color Meter II

• Lens; Nikon AF-S VR Micro-Nikkor • QP-card 101 105mm f/2.8G IF ED • Standard A4 oﬃce copier sheet • Lens; Nikon 35mm f/2.0 AF-D Nikkor • Color spectrophotometer; X-rite il Pro • Flash; Nikon SB-900 • Color management software; Proﬁler • Apple iPhone 5 5.0/Color Picker X-rite (Gretag Mac- beth) • Samsung Galaxy S4 • Image processing software; Adobe Photo- • Manfrotto tripod shop CS6

• Lastolite Plain Collapsible 1.8m x 2.15m • Screens; NEC SpectraView 271, UGRA White/Mid Grey Background certiﬁed

2.2.2 Implementation

The motif was the same throughout the photo session. Photos were taken in seven different lighting settings; sunlight, overcast, flash, incandescent light, fluorescent light, LED light and energy-saving light. The camera and the two smartphones were used under same conditions.

First, the person aimed to be photographed was placed in front of the gray background. The QP-card was attached close to the depicted object, see Section 3.3 for explanation of the QP- card. Then the color temperature of the site was measured by the color meter. Then the D700 with the 105 mm lens, i.e ordinary photo equipment for professional medical photography, was ﬁxed on the tripod. To achieve an ideal image, to be used as reference photo, the camera was manually white balanced and the ﬂash was used. Thereafter, overview and close-up photos, each of them both natural lighted and manually white balanced, of the person were captured.

Since the nevus was on the back of the person, the overview photo was taken of the entire back. Therefore the photographer stood at a distance of approximately 1 meter from the person. When the close-up photo was captured, a 1x magniﬁcation was achieved by placing the camera close to the region of interest. However, the distance was varied until a suﬃciently sharp photo was achieved.

The same procedure, but hand held, was repeated with the 35 mm lens. Photos were also taken with the iPhone 5 and the Galaxy S4 without any manual color temperature calibration. When all photos were taken with a certain light source, the light source was changed and then the procedure was repeated. In the smartphones the standard camera applications were used. In addition to the photos with the calibration card, photos with the white paper attached were taken for more basic color calibration purposes.

4 2.2 Photo session

2.2.3 Image processing The entire image processing and comparison was done on the SpectraView screens. The four different reference full-length photos (i.e. the cameras auto/manually white balanced and with/without flash) was further white balanced in Photoshop with the QP-card as color reference. They were compared side by side, and the manually white balanced with flash photo was chosen to be the main reference photo. The photos taken with the D700 had the gamut (a certain color space) Adobe RGB 1998, whilst the photos from the smartphones had the smaller sRGB gamut - giving less hues in the color representation, see Section 3.3 for further explanation of gamuts. Therefore, a visual comparison between the reference photo, converted into the different gamuts, were done, see Appendix Figure 1.

The pictures taken with the iPhone 5 and the Galaxy S4 in overcast lighting were also white balanced in Photoshop - ﬁrst with the QP card, and then with the white paper as color reference. The same procedure was repeated with the photos taken in incandescent lighting. The photos from the diﬀerent lighting settings were placed side-by-side for comparison.

The close-up photos taken in overcast lighting - both with the smartphone cameras and the D700 with the 35 mm lens - were compared to show possible diﬀerences in sharpness. A magni- ﬁcation of the nevus was cropped out of every photo.

Since the Galaxy S4 photos has a higher resolution and therefore are more detailed - the photos taken with the iPhone 5 was evaluated in the result. The equivalent photos captured by the Galaxy S4 can be found in Appendix Figure 2 and Figure 3.

Chapter 3

Technical review

Below follows diﬀerent aspects and properties that are essential in medical photography. The review evaluates how well smartphone cameras fulﬁlls the medical photography requirements. It also contains a table with a comparison between the D700, the Galaxy S4 and the iPhone 5.

3.1 Camera hardware

Some important camera parts that aﬀect the photo quality are the sensor size, the resolution of the sensor and the construction of the lens (including the aperture size). Common smartphone sensors are of size 1/3.2” (4.54 mm x 3.42 mm), whilst professional DSLRs1 have an APS-C 2 size (22.2 mm x 14.8 mm) or an even larger sensor - such as a full frame sensor (36.0 mm x 24.0 mm). A smaller sensor can not take in as much light as a larger sensor, which means that the smaller sensor is more receptive to noise [18, 19].

Given that the photos will be viewed on a computer screen, and that a computer screen resolution generally is no larger than 1080p (1920 x 1080 pixels) - the resolution of the camera does not need to exceed that value. Considering the possibility to zoom in on details in the picture, a camera resolution of at least 5 megapixels (MP) is necessary. However, a larger resolution does not guarantee a better image quality [11].

Another factor that affects the photo quality is the focal length. The focal length is a measure of how wide the angle of view is - the shorter the focal length, the wider the angle. The choice of focal length therefore depends on the wanted magnification [20, p. 1140]. A long focal length of e.g. 105 mm is good when photographing e.g. a nevus or an eye. If a larger area is depicted, a shorter focal length of e.g. 35 mm should be chosen [13]. Most smartphone cameras have a fixed, full frame equivalent, focal length of about 35 mm [21].

The aperture number is the size of the aperture opening and affects the depth of field (DOF). DOF is a measure of the distance in front of and behind the focus point - that is depicted sufficiently sharp. The lower the aperture number, the smaller the DOF [15, p. 586-589]. In medical photography it is important to have as much as possible in focus, i.e. a large DOF, since the purpose is to as good as possible reflect the situation [12,13]. Another factor that affects the DOF

1Digital Single-Lens Reﬂex cameras 2Advanced Photo System type C

7 Chapter 3 Technical review is the size of the optics - the smaller the optics, the larger the DOF. Even though smartphones have a small aperture number, they also have small optics - which gives them a large DOF [19].

3.2 Exposure

It is of great importance to take photos that are neither under- nor overexposed. The exposure depends on aperture, exposure time and light sensitivity, i.e. ISO settings. Since a large aperture means a big aperture opening, more light can get through the lens to the sensor. Since smartphones usually have a ﬁxed aperture it can not be changed in order to change the exposure of the photo [11, 12].

ISO is a measure of how receptive a sensor is to incoming light. The lower the ISO value, the more light is needed in order to obtain the same light density as a photo taken with a higher ISO value. However, a high ISO value causes noise in the photo. Therefore a low ISO value, about 200, is preferable in medical photography [11, 12].

Exposure time is the time a sensor is recording light. A long exposure time can generate blurry photos because of motion. This is not preferable in medical photography, as the images must be sharp. The exposure time is therefore recommended to be at least 1/f (focal length) of the lens [11, 12]. If the available light is limited a higher ISO value allows a shorter exposure time, although it makes the photo more noisy. In smartphones the automatic exposure function reg- isters the available light. Then it calculates a combination of exposure time and ISO value that gives an as balanced exposure as possible [20, p. 1140-1141].

3.3 Color temperature

Color temperature is a measure of the white lights hue, measured in degrees Kelvin. A high color temperature (>5000 K) gives bluish white, whilst low values (<3000 K) gives a yellowish or reddish white. In order to properly evaluate e.g. skin tones - a correct representation of the color temperature is crucial [12]. If the lighting source does not give a neutral color temperature, white balancing can be done with the help of calibration cards. A calibration card provides a color reference - most commonly it is white, neutral gray and black; but it can also have more or less colors or color levels. The white reference in QP-card 101 is 242 in all RGB values [22]. A white paper can also be used for calibrations purposes. However, it has an optical whitening eﬀect caused by ﬂuorescent chemicals and the paper can therefore be perceived whiter than it actually is [23]. See Appendix Figure 9 for measurements of whiteness in a QP-card and a white paper. The skin tones RGB value, measured between eyebrows, should be approximately 210 (red), 185 (green) and 155 (blue) for a Caucasian white person. The red, green and blue color units should relate to each other by R = 210 ± 20, G = R − 30 ± 10, B = G − 30 ± 10 [24].

The human eye automatically white balances to diﬀerent lighting. A camera does not have that capability, but tries to white balance the photo either automatically or manually. The automatic white balance function strives to give an as correct representation of the white hue as possible. However, to determine with conﬁdence that the white hue is represented in a correct way, manual tools should be used. Since the observer does not know what the correct white hue of the photo is, both the photo and the presentation screen should be calibrated to a standardized value, e.g. 5500K with the standardized name D55 [14, 25].

8 3.4 Lighting

3.4 Lighting

Factors like correct representation and homogeneous distribution of color temperature are highly dependent of the lighting sources and their positions. Uneven lighting generates a non-uniform color temperature and makes it impossible to white balance the image in a adequate way.

The choice of lighting technique depends on the motif. The most common ones in medical photography are ﬂat lighting, contour lighting and texture lighting. Flat lighting is uniformly distributed light. The light is directed from behind the camera. Flat lighting is preferable when photographing ﬂat motifs, e.g. lesions. In contour lighting the main illumination is unevenly distributed and therefore it can highlight e.g. deformations. Texture lighting emphasizes struc- tures in the skin [17, p. 88-94]

During medical photography in a studio or similar, external lighting in form of flashes is very common. This provides sufficient and uniformly distributed light in a homogeneous color temperature. Smartphones typically have a integrated LED-lamp which works as a flash. The LED-lamp does not provide the same homogeneity and light intensity as a professional flash does. However, it lights up the photo [14].

3.5 Comparison

Below follows a comparison between a professional medical camera and two smartphones [26–28].

Table 3.1: Technical comparison of diﬀerent cameras

Nikon D700 Apple iPhone 5 Samsung Galaxy S4 Resolution 12.1 MP (4256px x 2832px) 8 MP (3264px x 2448px) 13 MP (4128px x 2322px) Sensor size Full frame (36mm x 24mm) 1/3.2" (4.54mm x 3.42mm) 1/3.06" (4.71mm x 3.53mm) Crop factor 1x 7.61x 7.38x Focal length Interchangeable 4.1 mm (31 mm equivalent) 4 mm (31 mm equivalent) DOF Short to long, depends on lens Long Long ISO Manually adjustable Automatic Automatic Exposure time Manually adjustable Automatic Automatic Flash Interchangeable LED LED Optics High quality Limited quality Limited quality Gamut Adobe RGB 1998 sRGB sRGB

The D700 has a full frame sensor, whilst the smartphones have significantly smaller ones. Another property that differs is the focal length. Since the D700 has a interchangeable focal length it can be adapted more easily to different photo situations. The short focal lengths of the smartphones are however compensated by the crop factors. The exposure settings of the D700 are manually adjustable, whilst the smartphone cameras most commonly are automatic. Although, the automatic exposure of the smartphones are good. The optics of the D700 are of high quality. Due to the smartphone cameras smaller size, the quality of the optics are limited. Thus, that property gives the smartphone photos a large DOF. The gamut the smartphone cameras use is sRGB - which in comparison to Adobe RGB 1998 gives less colors in the photo.

Chapter 4

Result

4.1 Photos

Below follow some of the photos and measurements from the photo experiment. The abbreviation WB stands for white balance. More of the result can be found in Appendix.

Figure 4.1: Nikon D700, 105 mm lens, ﬂash, manually WB in overcast light. The left photo is non-edited whilst the right photo is WB in Photoshop as well, with the QP-card as reference - in order to give the best possible color representation.

Figure 4.2: iPhone 5, incandescent light. From left; non-edited, WB to QP-card, WB to white paper. The non-edited photo has a yellow hue which is calibrated in the other photos. Therefore they have a more natural skin tone.

11 Chapter 4 Result

Figure 4.3: iPhone 5, overcast light. From left; non-edited, WB to QP-card, WB to white paper. The white hue in the non-edited photo is incorrect, which is compensated for in the other photos.

Figure 4.4: Comparison of sharpness. From left; D700 - 35 mm lens, iPhone 5, Galaxy S4. The smartphone photos show good detail sharpness of the nevus.

Table 4.1: Measured RGB values of white reference and skin tone (measured inter-scapular)

White reference Skin RGBRGB Nikon D700, fig. 4.1 Reference photo 241 242 241 210 164 141 iPhone incandecent, fig. 4.2 Non-edited 254 255 212 224 165 99 WB with QP-card 252 254 254 220 163 130 WB with white paper 255 255 246 232 182 142 iPhone overcast, fig. 4.3 Non-edited 202 224 223 179 145 122 WB with QP-card 222 234 230 204 164 139 WB with white paper 224 233 230 207 166 144

12 4.2 Guidelines

4.2 Guidelines

This section contains the developed guidelines with suggestions of how inexperienced persons could use smartphones in telemedical photography.

It is recommended that the user has a smartphone camera with at least 5 MP resolution. The user should also be equipped with a color calibration card, e.g. a QP-card, or a white paper. The user should also have an object of known size, e.g. a ruler, a credit card/drivers license or a coin. When photographing the automatic exposure function should be used. The zoom function should be avoided, unless the smartphone possesses an optical zoom.

Preparation for photography

1. Preparation The camera lens should be cleaned from potential particles, grease and condensation.

2. Surroundings Distracting elements should be removed from the region of interest (ROI), e.g. jewelries and glasses. If possible and relevant, clothes and make-up should be removed.

3. Background The patient should if possible stand in front of a monochromatic wall. Otherwise the patient should be placed in front of an as neutral background as possible.

4. Lighting To achieve an even light distribution the light should come from the same direction as the picture is taken, i.e. from behind the camera. Mixed lighting from light sources with diﬀerent color temperature should be avoided. Presented below are three diﬀerent lighting situations, starting with the most preferred option:

• Natural lighting The person should be placed so that the incoming light comes from behind. Soft sunlight or overcast is more preferable than direct sunlight.

• External sources, e.g. ﬂuorescent or incandescent light Make sure that the external light source does not cause shadows. If possible, place the lighting source behind the camera, and direct it against the problem area. If the lighting source is not adjustable, place the patient where the light causes fewest shadows around the ROI.

• Integrated ﬂash If no lighting sources are available, i.e. it is dark - the integrated ﬂash should be used. The camera should be directed straight towards the problem area.

13 Chapter 4 Result

Photography 5. Overview photo The calibration card or the white paper should be placed near the ROI, see Figure 4.5. The photographer should stand approximately one arms length (∼ 1m or 3ft) away from the patient - or until the camera screen includes enough of the patients body, so that it is clearly visible where the ROI is. The photographer should aim to stabilize the smartphone before taking the picture, see Figure 4.5 for an example method. 6. Close-up photo The photographer should try to achieve a 1x magniﬁcation, i.e. the screen should only include the ROI with some surroundings. For size reference, a ruler or a credit card could be used as a scale. The photographer should achieve an as sharp photo as possible. If the camera is placed too close to what is depicted the camera can not generate a sharp photo. Therefore it is recommended to have at least one palm width of distance between the camera and what is depicted, see Figure 4.6 for an example method. The photographer should take several photos and review them, in order to ensure that a suﬃciently sharp photo is achieved.

Figure 4.5: Example: how to take Figure 4.6: Example: how to take a full length photo a close-up photo

Post photography The photos should be transferred to a medical professional for evaluation.

7. Image processing Both the overview and the close-up photos should be white balanced with the color calibration card/white paper as reference point. Depending on prerequisites and situation, diﬀerent tools for white balancing could be used, e.g. a smartphone application or a computer with an image processing software. 8. Observer For the best opportunity to correctly diagnose the patient with the help of the photo, the observer should use a screen with high resolution and good color representation.

14 Chapter 5

Discussion

As the studies referred to in Section 1.1 show - telemedical photography is a rapidly developing area. Much research is done simultaneously by both academics and commercial companies, which shows that the area is interesting. None of the studies indicate that telemedical photography should not be investigated further.

5.1 Evaluation of the result

There are no major differences between the photos taken with the different smartphone cameras. Both cameras meet the required specifications and are capable of capturing detailed photos.

Both photos in Figure 4.1 represent the colors in a good way. This means that the built-in PRE-setting for white balance in the D700 is of high quality - although it does not give the exact RGB values of the QP-card. In the right photo this is compensated for, by adjusting the white, gray and black color in the QP-card to its correct values. This gives the best possible color representation. The gray hue of the background is almost equal throughout the entire photo. This shows that the light is homogeneously distributed, and is explained by the ﬂash usage.

In Figure 4.2 the non-edited photo has a yellow hue, i.e. the color temperature is too warm. The edited photos shows that the smartphone photos, taken under an extreme lighting condition, can give a suﬃciently good color representation - after being white balanced with the QP-card or the white paper as white reference. In Figure 4.3 the white paper of the non-edited photo has a gray tone. The edited photos shows that the photos taken under natural lighting conditions give good color representation after being white balanced - both with the QP-card and the white paper as white reference. In both ﬁgures, the white balanced photos have a more natural skin tone. This is further shown in Table 4.1. The table displays that the white color and the skin tone, both white balanced to the QP-card and the white paper, are within an acceptable RGB value range - according to the reference values mentioned in Section 3.3. As expected, the QP-card generates a more adequate color representation. This is explained by its more color levels and the more correct white hue.

Because of the white papers optical whitening eﬀect, it is perceived whiter than it actually is - a phenomena the camera does not register. Since the paper is very thin, it can get a more adequate color representation by being folded once or twice - because of less light transmission through the paper, see Appendix Figure 9 for measurements of this.

15 Chapter 5 Discussion

By comparing the overcast and incandescent photos, it can be concluded that the lighting source aﬀects the deﬁnite color representation. However, via a QP-card or an ordinary white paper in addition to an image processing software - good results can be achieved under extreme lighting conditions too.

Figure 4.4 shows the smartphone photos in comparison to the professional camera. It is clearly visible that the smartphones provides very sharp close-up photos. The D700 was set to a ﬁxed aperture value of 5.6 in order to be comparable with the smartphones. This gave the D700 a very short DOF. The photo taken with the D700 was therefore captured from a larger distance, in order to increase the DOF. The larger distance explains the smudgy appearance. Normally, the D700 can give sharper photos than what is shown in the photo - by raising the aperture value to 11-22 and thereby achieving an even larger DOF. However, the comparison shows that smartphone cameras can produce photos that are sharp enough for usage in medical photography.

5.2 Evaluation of the method

During the implementation of the method, a proof of concept was achieved. This since the person photographing was not an experienced photographer, e.g. the person had no prior experience of handling the smartphone camera in a clinical setting. The photo session was beneﬁcial as it provided helpful experiences of how to handle the camera, which had been hard to obtain by only studying available reports on the subject. An advantage of the photo shoot was the realistic lighting settings. This showed that the proposed guidelines can provide good photos in everyday situations.

It was difficult to find scientifically approved articles regarding medical photography guidelines and technical specifications. Although the used material is published by trustworthy organizations or at company web-pages. An extension of the method could have been to test more cameras, in order to confirm the concept further. However, even though only two different smartphones were used - they were representative for current, widely used models. However, they were also considered to be top of the line models. There were smartphones with cameras not as advanced that could have been used instead, that most likely should have given similar result, considering the evaluated parameters. Another extension could have been to photograph different motifs. Since only a flat one was photographed it was irrelevant to analyze the perspective distortion caused by smartphone cameras. However, the selected motif, i.e. the nevus, shows that the smartphone cameras are capable of separating similar skin tones. A limitation in the method lies in how to ensure the consistency. When a person is inexperienced or does not have a reference picture, it can be hard to determine if the sharpness and reproduction ratio are sufficiently good.

Since no external persons have tested the proposed guidelines - it is not ascertained how per- ceptive and easily followed they are. An expansion of the method could therefore have been to make it more extensive, e.g. both inexperienced persons and medical experts could have tried the guidelines. Furthermore, if these guidelines will be used as diagnostic support, they should ﬁrst be evaluated and conﬁrmed by medical professionals.

16 5.3 Technical aspects

5.3 Technical aspects

Throughout the process the importance of good lighting conditions has been evident. Since the camera performs best in automatic mode, the use of external lighting sources is the easiest way to take high qualitative photos. Most advantageous would be to use advanced lighting equipment with known color temperature. Thus considering that the guidelines aim to simplify medical photography - the tried, easy accessible lighting sources prove that common people can take qualitative photos. The white paper used in the method did handle the incorrect color temperature derived from the chosen lighting sources in a convenient way.

The guidelines recommend to place the lighting source in the same direction as the photo is taken, but in some situations it is not possible to adjust the light position, e.g. ceiling lamps. This can generate unwanted shadows. A solution could be to either lay or tilt the person or body part in under the lamp. A side eﬀect of this could be perspective distortion. The photographer should therefore prioritize what is most important in that kind of situation. Another common issue is mixed light, which is recommended to be avoided. However, to achieve a sharp photo much light is crucial - and since sharpness is more important than proper color representation, a lot of mixed light is better than limited homogeneous light.

The diﬀerence in gamut is a limitation in the smartphone camera, and the current sRGB color space is not expected to be extended to e.g. Adobe RGB 1998. With that said, a wider gamut is not essential in medical diagnostics. The small aperture and sensor size, as well as the ﬁxed focal length of smartphone cameras are non-negligible facts. These properties are limitations and are not expected to be changed - because of the desired small size. The fact that smartphones have a long DOF is an advantage when inexperienced persons are taking photos, since it makes it easier to achieve a sharp close-up photo, in an everyday setting. The high resolution is also an advantage - but in further development it would be better to enlarge the pixel size before increasing the resolution even more - in order to improve the light sensitivity. Overall, smartphone cameras are of high quality and they have the ability to provide high quality photos.

5.4 Future possibilities

Considering the current technological development, the camera technology will not be the limit- ing factor for smartphones as medical photography devices. Simultaneously with the smartphone development, the telemedical diagnostics will increase in importance. Therefore these guidelines provide a step towards a more modern, eﬃcient, easy accessible and patient-centered health care system. The challenge lies in implementing and integrating the guidelines into a greater system.

The workload at health care facilities is big, and therefore patients risk to get insuﬃcient care. In many specialized care situations, e.g. dermatology, some of the diagnostics done at health care facilities could advantageously be done remotely instead. The development of people taking medical photos with smartphones would also facilitate the health care for people that live in rural areas or in developing countries. This would mean that diagnostics could be done by specialists in remote cities or countries - that the health care could become more global and available regardless of localization and socioeconomic conditions.

17 Chapter 5 Discussion

An extended use of telemedical photography could also facilitate the follow-up of the development of diﬀerent conditions, e.g. malign melanoma or skin infections. A continuous self-assessment could complement photo examinations done by medical professionals, and improve the patients anamnesis. Another thought application area is to implement the guidelines into a smartphone application. The application could be connected to a personal health care provider, the emer- gency care or an advice service, e.g. the Swedish advice service Sjukvårdsupplysingen. This would complement verbal or written diagnostic material. In order to help inexperienced persons to evaluate the quality of their photos, reference photos and frequently asked questions could be added to the application service - in addition to the guidelines. This would improve the consistency, as well as the quality of the photos.

Other areas where the guidelines could be applied are within criminology and insurance cases, e.g. documentation of victims injuries. Some important factors that should not be neglected, in the aforementioned and other possible areas, are the patient safety and integrity aspects. These factors are not discussed further, because of the time limitation and extent of this project.

18 Chapter 6

Conclusion

Current smartphones satisfy the required technical properties such as resolution, light sensitivity and color representation - and future models are assumed to be even better. This conﬁrms that the technology of current smartphone cameras are suﬃciently good to be used in medical photography. The drawbacks of introducing smartphones as a medical photography device are negligible when taking all the advantages and possibilities in consideration.

In an everyday situation, the guidelines give supervision for an inexperienced person. They are supposed to be easy to follow and should provide improvement on a general level. However, the fact that the guidelines are general and not yet thoroughly tested should not be overlooked.

An area that should be investigated further is how to implement the use of smartphone cameras in health care services. That requires an accurate and thorough analysis of safety and integrity aspects. Furthermore, the usability of the guidelines should be developed and improved. This could be done by adapting and extending them to diﬀerent medical situations.

Chapter 7

References

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[12] J. Khavkin and D. A. Ellis. Standardized photography for skin surface. Facial Plast Surg Clin North Am, 19(2):241–6, 2011. [13] J. R. Nayler. Clinical photography: a guide for the clinician. J Postgrad Med, 49(3):256–62, 2003. [14] Jonas Brane. Studio and ward protocol 2014. 2014. [15] Michael R. Peres. Focal Encyclopedia of Photography. Elsevier Inc., 4th edition, 2007. ISBN 13: 978-0-240-80740-9. [16] John Paul Vetter. Biomedical Photography. Butterworth-Heinemann, 1992. ISBN: 0-240- 80084-2. [17] Henry Lou Gibson. Medical Photography. Eastman Kodak Co., 1973. ISBN 13: 978- 0879850760. [18] Simon Crisp. Camera sensor size: Why does it matter and exactly how big are they? http://www.gizmag.com/camera-sensor-size-guide/26684/, 2013. [Online; retrieved 2014-04-01]. [19] Brian Klug. Understanding Camera Optics & Smart- phone Camera Trends. http://www.anandtech.com/show/6777/ understanding-camera-optics-smartphone-camera-trends, 2013. [Online; retrieved 2014-04-11]. [20] Hugh D Young, Freedman Roger A., and A. Lewis Ford. University Physics. Jim Smith, 13th edition, 2012. ISBN 13: 978-0-321-76218-4. [21] Diego Noriega Mendoza. A Tour of the Hardware Found in Mod- ern Smartphone Cameras. http://petapixel.com/2013/08/01/ a-tour-of-the-equipment-found-in-modern-smartphone-cameras/, 2013. [Online; retrieved 2014-04-11].

[22] QP-card. Qp-card 101. http://www.qpcard.com/en_b2c/qpcard101.html/, 2014. [23] He Shi, Hongbin Liu, Yonghao Ni, Zhirun Yuan, Xuejun Zou, and Yajun Zhou. Review: Use of optical brightening agents (obas) in the production of paper containing high-yield pulps. BioResources, 7(2), 2012. [24] Lee Varis. Skin: the complete guide to digitally lighting, photographing, and retouching faces and bodies. Jim Smith, 2nd edition, 2010. ISBN-13: 978-0470592120.

[25] CIE. Equivalent white light sources and cie illuminants. http://www.cie.co.at/, 2008. Vol. 17, No. 5.

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22 Chapter 7 References

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Appendix

Photos

Figure 1: Comparison of the color representation with diﬀerent gamuts. From left: Adobe RGB 1998 - white balanced, Adobe RGB 1998 - non-edited, sRGB converted from Adobe RGB 1998, sRGB straight from D700

Figure 2: Galaxy S4, overcast. From left; non-edited, WB - QP-card, WB - white paper

1 Appendix

Figure 3: Galaxy S4, incandescent. From left; non-edited, WB - QP-card, WB - white paper

2 Photos

(a) LED-light (b) Built-in ﬂash (c) Sunlight

(d) Florescent-light (e) Energy-saving lamp

Figure 4: Samsung Galaxy S4 photos taken in diﬀerent light settings.

3 Appendix

(a) LED-light (b) Built-in ﬂash (c) Sunlight

(d) Florescent-light (e) Energy-saving lamp

Figure 5: Apple iPhone 5 photos taken in diﬀerent light settings.

4 Photos

(a) LED-light (b) Incandecent light (c) Sunlight

(d) Fluorescent-light (e) Energy-saving lamp

Figure 6: Nikon D700 close-up photos taken in diﬀerent light settings.

5 Appendix

(a) LED-light (b) Built-in ﬂash (c) Sunlight

(d) Florescent-light (e) Overcast (f) Overcast

Figure 7: Apple iPhone 5 close-up photos taken in diﬀerent light settings.

6 Photos

(a) LED-light (b) Built-in ﬂash (c) Sunlight

(d) Florescent-light (e) Overcast (f) Overcast

Figure 8: Samsung Galaxy S4 close-up photos taken in diﬀerent light settings.

7 Appendix

Measurements

Figure 9: Measurements of whiteness

Lighting Color temperature Incandescent 2600K Energy-saving lamp 2800K Flourescent 3370K Overcast 4900K Sunlight 5000K LED light 6700K

Table 1: Measured color temperature of diﬀerent light sources

The SB-900 ﬂash has a color temperature of 5500K [26]. The color temperature of the Galaxy S4 and the iPhone 5 was not measured. [3, 29]