Focus Stacking Associated key issues: - Depth-of-Field - Image Quality Overview 1. Reproduction of slides (pages 2-11) 2.Two-page summary (pages 19-20) Detailed notes 1. Depth-of Field (pages 12-15) 2. Large Prints (page 14) 3. Focus stacking (page 16) 4. Resolution & Diffraction Limit (pages 17-18) Graeme James 1 May 2017 millimetres stop - / f / 2 1/C x f x 1/C ‘C’ number a in just is ) distance distance DoF up to H up to - hyperfocal the image to be inbe to image the Field ( Field field is from H to ∞ H to from is field - - of - of field - - perceive of - extends from H/2 ∞ H/2 to from extends focus the camera to H and now the now H and to camera the focus - The value for H depends on depends H for The value With the camera focused at infinity at focused camera the With we (∞) camera the H from distance a to focus depthThe Re DoF focus ever need only we principleIn close from camera the as the is knownH indefining number crucial is a and depth Page Page 2 Depth 1. 2. 3. 4. 5. ”) Not toscaleNot (defined by the “Crop Factor “Crop the (defined by sensor or film size size film or sensor The The distance and viewing size Image 1. 2. Combining the above factors we get 1/C = 50 x (Crop Factor) x (Crop 50 = 1/C get we factors above the Combining What is ‘’C’’? What The value of C depends on the level of detail you can see. see. can you detail of level onthe depends of C value The factors: maintwo affects This diagonal. image thetimes 1.5 is around distance a comfortable prints, or images For Page Page 3 8 f mm @ 8m 23m 16m 12m 2.8m 113m H 0.7m** formula stop; stop; - / / f 2 f distance distance 75mm 50mm 35mm 25mm 10mm 360mm 4.15mm* Standard lens Standard 2.2 giving H = 2.8m, the same as a compact camera H compact as the a 2.2 = 2.8m, same giving f x (Crop Factor) x Factor) x (Crop 1 2 1.5 4.8 7.2 50 Hyperfocal 0.14 0.65 = H Crop factor Crop The (Full (Full Frame) almost almost C - is x 10 inch film inch 10 x Camera Format Camera 8 Format Medium 35mm APS 4/3 Micro Compact 6 iPhone * This is wider than a standard lens and equivalent to a 29mm Full Frame lens Full Frame to 29mm a equivalent lens and standard a is wider than * This at aperture fixed hasiPhone a 6 ** Thelens → → iPhone 6 iPhone traditionally. 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An exception is the view is exception oflargeAnthe cameras. majorityfor least * At Depth of controllingmeans additional allowswhich camera Field Overview Field - of - Page Page 5 Depth C - 5 5 stops - 6400 ISO 6400 By 4 By FF and and APS FF Loss with both both Losswith DLSR design DLSR 4 4 stops - C sensors C - Noise performance highly Noise performance 1600 ISO 1600 dependent on sensor design sensor on dependent By 2 By APS Some Some with loss 2 2 stops - Typical reduction in performance with ISO with in performance reduction Typical 400 ISO 400 By 1 By ≥ 13 stops 13 ≥ Mirrorless design Mirrorless Not an issue for most cameras most issue Not an for cameras most issue Not an for sensor @ 100 100 sensor@ ISO High performance performance High Noise sensitivity Dynamic range Dynamic Main attributes Main Colour rendition or rendition Colour Page Page 6 → Camera Image Quality (IQ)Quality Image Camera The sensorI. lens perfect diff sensor sensor resolution f = – lens resolution resolution lens stop - Diffraction limit, Diffraction rop Factor rop C where where s fixed in valuein s fixed stop i - f reduces with f with reduces The resolution and diffraction limit a limit with anddiffraction resolution And megapixel count megapixel And – IQ (cont.) 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Points to note: to Points Page Page 8 Camera IQ (cont Camera lens III.The the From * )/H f - focus up Subjectup - camera movement. movement. camera = 2 (S+X (S+X) = x x minimise 2 www.youtube.com/watch?v=NgoUF1DA_T4 https:// stop - f / ) /H and at ‘S+X’ where DoF where at‘S+X’ /H and ) 2 f f - = 2 x 2 x S x (S= 1 stabilisation 0 x (Crop factor) x x factor) x 0 (Crop camera 5 image , , = H for your lens/camera combination lens/camera your for diff f distance Field at ‘S’, where where DoF ‘S’, at Field - of - at ‘S’ and ‘S+X’, with the aid of a test target, determine how far to rotate the focusing ring between eachbetween ring the shot focusing torotate determine how far target, the a test with aidof and ‘S’ ‘S+X’, at of Field at S to determine how many images are required to have the entire in subject the entire have to are images many required how determine at to Field of S stop set at set stop - - f Hyperfocal DoF up : stack the images, go to Edit > Auto Align followed by Edit > Auto Blend. Flatten. Done! Blend. > Auto Flatten. by Edit Align followed > Auto toEdit the go : images, stack - : you will need to add ‘elements plus’. For a demonstration see see demonstration a For plus’. add : need ‘elements will you to Detailed procedure for Focus Stacking of Extended Close of Extended Stacking Focus for procedure Detailed focus (gently!) between shots rotating the focus ring by the amount determined in in ring amountdetermined 3.3. the by focus the shotsrotating between focus(gently!) - e Basic set Basic image tripodturnandany on offCamera ofsubject,mm X, ofin subject, in S, extent mm, front to Distance Calculate Depth Calculate the From to release shutter remote by possible, if of images, aseries take ‘S+X’, Beginning at R hotoshop Page Page 9 P Elements 1. X extent of subject the of front S the from a distance length f, on tripod, lens focal a Camera 1. 2. settings 2. Camera of the optimum the settings Determine and= ISO 100 3. Calculations Depth Calculate 1. 2. 3. capture Image4. 3. step from positions focus as determined images ofdifferent series at a on take manual With the focus camera 1. 2. processing Post 5. one images ofinto set Combine the In In ) /H )/H = 6.6mm f - stop - f (S+X = 18m = ) /H /H = mm 6 ) f - = = 11= stop - f diff / f = 2 (S+X) 2 = 2 f 2 = = S2(S 1 , H , = 50 ) =14MP → DxO distance from from ( Mpix - Settings: ISO = 100 Crop factor = = 1 = factor 100 ISO Settings: Crop P Hyperfocal 24MP with frame lens full 50mm Page Page 10 Example of focus stacking focus of Example Camera: Subject: → S =21cm DoFSubjectdistance, 6cm X DoF= at ‘S+X’ Subjectextent, Page 11 Post Processing Post Page 12 Depth-of-Field The basic concept of Depth-of-Field In the image below the camera is focused at infinity on the most distant part of the scene. While the image is strictly focused only at the plane at infinity, to the human eye much of the scene in the mid-ground is perceived to be in focus.