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FORUMS Photography Talk by Genre General Photography Talk
Thread started 30 Apr 2017 (Sunday) 11:53
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Is it possible to tell Subject Distance from EXIF data?

 
PCousins
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Weston-Super-Mare (UK)
Post has been edited 4 months ago by PCousins.
Apr 30, 2017 11:53 |  #1

The image below of a Song thrush is heavily cropped. The bird was a fair distance away and considering it was taken at 1/160s I did not expect it to be so sharp. I was interested in knowing how far the bird was from me, so I went to the exif data as there is so much information and there was no indication......So out of interest only does anyone know if at all possible can you tell distance to subject????


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Mark IV
EF500mm f/4L IS USM +1.4x
ƒ/6.3 700.0 mm 1/160 800 Flash (off, did not fire) Hide EXIF
Make - Canon
Orientation - Horizontal (normal)
X-Resolution - 350 dpi
Y-Resolution - 350 dpi
Software - Digital Photo Professional
Date and Time (Modified) - 2017:04:29 10:11:29
Artist - XXXXXXXXXXXXXXX
YCbCr Positioning - Centered
Copyright - Paul Cousins Photography
ISO Speed - 800
Exif Version - 0221
Date and Time (Original) - 2017:04:29 10:11:29
Date and Time (Digitized) - 2017:04:29 10:11:29
Components Configuration - Y, Cb, Cr, -
Exposure Bias - -1/3 EV
Metering Mode - Spot
Sub Sec Time - 09
Sub Sec Time Original - 09
Sub Sec Time Digitized - 09
Flashpix Version - 0100
Color Space - sRGB
Custom Rendered - Normal
Exposure Mode - Auto
White Balance - Auto
Scene Capture Type - Standard
Macro Mode - Normal
Self Timer - Off
Quality - Fine
Canon Flash Mode - Off
Continuous Drive - Continuous, High
Focus Mode - AI Servo AF
Canon Image Size - Unknown (-1)
Easy Mode - Manual
Digital Zoom - None
Contrast - +1
Saturation - +2
Metering Mode - Spot
Focus Range - Not Known
Canon Exposure Mode - Aperture-priority AE
Lens Type - Canon EF 500mm f/4L IS
Max Focal Length - 700 mm
Min Focal Length - 700 mm
Focal Units - 1/mm
Max Aperture - 5.7
Min Aperture - 45
Flash Activity - 0
Flash Bits - (none)
AESetting - AE Lock
Zoom Source Width - 0
Zoom Target Width - 0
Manual Flash Output - n/a
Color Tone - +1
SRAWQuality - n/a
Auto ISO - 100
Base ISO - 800
Measured EV - 9.25
Target Aperture - 6.3
Target Exposure Time - 1/161
White Balance - Auto
Slow Shutter - None
Sequence Number - 0
Optical Zoom Code - n/a
Flash Guide Number - 0
Flash Exposure Comp - 0
Auto Exposure Bracketing - Off
AEBBracket Value - 0
Control Mode - Camera Local Control
Measured EV2 - 8.875
Bulb Duration - 0
Camera Type - EOS High-end
NDFilter - n/a
Canon Image Type - Canon EOS-1D Mark IV
Canon Firmware Version - Firmware Version 1.1.4
Serial Number - 530502138
Canon Model ID - EOS-1D Mark IV
AFArea Mode - Single-point AF
Num AFPoints - 27
Valid AFPoints - 27
Canon Image Width - 3440
Canon Image Height - 1314
AFImage Width - 3440
AFImage Height - 1314
AFArea Widths - 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151 151
AFArea Heights - 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212 212
AFArea XPositions - -528 -283 -29 231 495 749 1013 1273 1527 -685 -425 -161 99 363 622 881 1145 1405 -528 -283 -29 231 495 749 1013 1273 1527
AFArea YPositions - -246 -246 -246 -246 -246 -246 -246 -246 -246 103 103 103 103 103 103 103 103 103 452 452 452 452 452 452 452 452 452
AFPoints In Focus - 14
AFPoints Selected - (none)
Bracket Mode - Off
Bracket Value - 0
Bracket Shot Number - 0
Raw Jpg Size - Large
Long Exposure Noise Reduction2 - On
WBBracket Mode - Off
WBBracket Value AB - 0
WBBracket Value GM - 0
Live View Shooting - Off
Flash Exposure Lock - Off
Lens Model - EF500mm f/4L IS USM +1.4x
Internal Serial Number - R024732
Tone Curve - Standard
Sharpness - 5
Sharpness Frequency - n/a
Sensor Red Level - 0
Sensor Blue Level - 0
White Balance Red - 0
White Balance Blue - 0
Color Temperature - 5800
Picture Style - User Def. 1
Digital Gain - 0
WBShift AB - 0
WBShift GM - 0
Measured RGGB - 594 1024 1024 462
Color Space - sRGB
Sensor Width - 5120
Sensor Height - 3318
Sensor Left Border - 152
Sensor Top Border - 50
Sensor Right Border - 5047
Sensor Bottom Border - 3313
Black Mask Left Border - 0
Black Mask Top Border - 0
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Black Mask Bottom Border - 0
Color Data Version - 7 (500D/550D/7D/1DmkIV)
White Balance RGGB Levels - 2001 1024 1024 2158
Color Temperature - 3896
WB_ RGGBLevels Auto - 2001 1024 1024 2158
Color Temp Auto - 3896
WB_ RGGBLevels Measured - 1995 1027 1020 2151
Color Temp Measured - 3896
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Color Temp Daylight - 5200
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Color Temp Tungsten - 3200
WB_ RGGBLevels Fluorescent - 1876 1024 1024 2236
Color Temp Fluorescent - 3704
WB_ RGGBLevels Kelvin - 2294 1024 1024 1477
Color Temp Kelvin - 5792
WB_ RGGBLevels Flash - 2378 1024 1024 1432
Color Temp Flash - 6185
Average Black Level - 2048 2048 2048 2048
Raw Measured RGGB - 144758 253745 253469 115325
Per Channel Black Level - 2048 2048 2047 2047
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Linearity Upper Margin - 10000
AFMicro Adj Mode - Adjust by lens
AFMicro Adj Value - 0
Peripheral Lighting - On
Chromatic Aberration Corr - On
Peripheral Lighting Value - 0
Original Image Width - 4896
Original Image Height - 3264
Peripheral Lighting Setting - Off
Auto Lighting Optimizer - Off
Exposure Level Increments - 1/3-stop set, 1/3-stop comp.
ISOSpeed Increments - 1/3 Stop
ISOSpeed Range - Enable; Max 12800; Min 100
AEBAuto Cancel - On
AEBSequence - 0,-,+
AEBShot Count - Unknown (7); 0
Spot Meter Link To AFPoint - Disable (use center AF point)
Safety Shift - Enable (Tv/Av)
Usable Shooting Modes - Disable; Flags 0xfc
Usable Metering Modes - Disable; Flags 0xf0
Exposure Mode In Manual - Specified metering mode
Shutter Speed Range - Enable; Hi 1/8192; Lo 32
Aperture Range - Disable; Closed 91; Open 1
Apply Shooting Metering Mode - Enable; 1; 2; 1; 133; 51; 0; 1
Flash Sync Speed Av - Auto
FEMicroadjustment - Disable; 0; 8; 0
AEMicroadjustment - Disable; 0; 8; 0
Long Exposure Noise Reduction - On
High ISONoise Reduction - Off
Highlight Tone Priority - Disable
Auto Lighting Optimizer - Disable
ETTLII - Average
Shutter Curtain Sync - 1st-curtain sync
Flash Firing - Fires
View Info During Exposure - Disable
LCDIllumination During Bulb - Off
Info Button When Shooting - Displays shooting functions
USMLens Electronic MF - Disable after one-shot AF
AIServo Tracking Sensitivity - Unknown (254)
AIServo Image Priority - 1: AF, 2: Drive speed
AIServo Tracking Method - Main focus point priority
Lens Drive No AF - Focus search on
Lens AFStop Button - Spot AF
AFMicroadjustment - Adjust by lens; 8; 0; 0; 0
AFPoint Area Expansion - Surrounding AF points
Multi Controller While Metering - Off
Selectable AFPoint - 45 points
AFPoint Auto Selection - Control-direct:disable/Main:di​sable
Switch To Registered AFPoint - Disable
AFPoint Display During Focus - Off
AFPoint Brightness - Brighter
AFAssist Beam - Emits
Orientation Linked AFPoint - Select different AF points
Mirror Lockup - Disable
Continuous Shooting Speed - Enable; Hi 10; Lo 3
Continuous Shot Limit - Disable; 99 shots
Shutter Button AFOn Button - AE lock/Metering + AF start
AFOn AELock Button Switch - Disable
Quick Control Dial In Meter - Exposure comp/Aperture
Set Button When Shooting - Normal (disabled)
Manual Tv - Tv=Main/Av=Control
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Lock Microphone Button - Protect (hold:record memo)
Button Function Control Off - Normal (enable)
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Focusing Screen - Ec-CIV
Timer Length - Disable; 6 s: 6; 16 s: 16; After release: 2
Short Release Time Lag - Disable
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Related Image Width - 3440
Related Image Height - 1314
Compression - JPEG (old-style)
Thumbnail Offset - 6246
Thumbnail Length - 4759
Camera ID - 72157603810225532
Camera Type - Digital SLR
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BigAl007
Cream of the Crop
Joined Dec 2010
Repps cum Bastwick, Gt Yarmouth, Norfolk, UK.
Apr 30, 2017 11:59 |  #2

Some lenses do seem to pass distance information to the body, as it is used by the ETTL flash system. This is then also recorded in the EXIF data, as part of the "Maker's notes" IIRC. The issue is that it seems as if the data is very unreliable, and is so of virtually no practical use. it may be of a little more use for images shot close in, but much over ten feet seems to result in almost random results.

Alan


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Wilt
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Apr 30, 2017 13:15 |  #3

I have a number of lenses that pass distance info that is recorded into the EXIF. I discovered, very rapidly, that distance info is PATHETIC!


I have done testing multiple times, using different lenses, and using a lot of distances. The consistency of EXIF distance is 'SELDOM RIGHT', although it might be consistent.

In this test, I put markers every 1' as measured with a tape out to about 25', took a photo, and checked the EXIF for all photos"
http://photography-on-the.net ...showthread.php?p=16​743446

I also took a 70-200mm and shot photos at maybe 3m intervals...the distances only updated at intervals (without changed EXIF values for intermediate distances)!
http://photography-on-the.net ...showthread.php?p=16​502870

EXPERIMENT to learn best for your lens! Measure, with your camera on tripod, to something the EXACT distance as the last number of the scale of your lens. My Canon 100mm has last distance 15', my Tamron 28-75 has last distance 7'.) AF at that point and see where it lands. Now put something 1' closer in front of your original target, and as you press the focus button note how much/little the scale shifts for a 1' change.


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MalVeauX
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Apr 30, 2017 13:45 |  #4

I'm guesstimating approximately 17 feet.

Very best,


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Wilt
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Post has been edited 4 months ago by Wilt.
Apr 30, 2017 13:53 |  #5

Can you give us these two values?:


  1. what is the estimated length of bird (beak to tail) at life size?
  2. what is the estimated length of the bird as shot on sensor (size in mm?, or what percentage of the entire frame width?)


With both answers and knowing the FL of the lens used, it is indeed possible to compute the approximate distance.

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Archibald
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Post has been edited 4 months ago by Archibald.
Apr 30, 2017 14:12 |  #6

I agree with Alan and Wilt that the distance info in the EXIF is very unreliable.

You could estimate the distance if you need to know it, from a simple formula based on similar triangles. It is

SubjSize/Distance = ImgSize/FocalLength. You can use feet on one side and mm on the other side of the equation.

Solving for distance gives Distance = SubjSize*FocalLength/I​mgSize.

So if the bird is 6" long and its image is 5mm on the sensor, then the Distance is 0.5Ft * 700mm / 5mm = 70 ft.

EDIT - sorry, Wilt, didn't see your post in time.


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PCousins
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May 01, 2017 03:53 |  #7

Thank you to all for your investigations/help...​.

You can see from my EXIF data that there is a hell of a lot of useless information there yet distance to subject comes down to a calculation.

I am not at all any good at estimating distances, I tend to think on the lines of I'm 6ft tall, something which is approx 10 of me away is 60ft. I would say that Archibald & Wilt's calculation is fairly accurate.

In this example the thrush is about 6" and looking at the photo on camera I have just checked it is 5 mm so Archibald was spot on.
Thanks Again


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sidknee
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May 01, 2017 05:06 |  #8

This might be useful here,

http://www.scantips.co​m/lights/subjectdistan​ce.html (external link)


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SevenD2
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May 09, 2017 19:21 |  #9

Focus point plug-in in Lightroom.




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Wilt
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May 09, 2017 21:52 |  #10

SevenD2 wrote in post #18350458 (external link)
Focus point plug-in in Lightroom.

The focus point recorded in EXIF is horridly flawed and lacking in accuracy. In post 3 I reported two other posts of mine testing the focus distance precision vs. reality. And the scantips article linked in post 8 agrees with my testing:

"the DSLR Exif data may tell you Focus Distance, except you should realize that the focus distance reported is often seriously incorrect, especially for zoom lenses. "


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Archibald
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May 09, 2017 23:17 |  #11

Wilt wrote in post #18350576 (external link)
The focus point recorded in EXIF is horridly flawed and lacking in accuracy. In post 3 I reported two other posts of mine testing the focus distance precision vs. reality. And the scantips article linked in post 8 agrees with my testing:

"the DSLR Exif data may tell you Focus Distance, except you should realize that the focus distance reported is often seriously incorrect, especially for zoom lenses. "

This is my experience too.


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Picture editing OK

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Tom ­ Reichner
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May 11, 2017 20:22 |  #12

.

SevenD2 wrote in post #18350458 (external link)
Focus point plug-in in Lightroom.

I thought that we had already dismissed that earlier in the thread, as being terribly inaccurate.


.


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Is it possible to tell Subject Distance from EXIF data?
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