"Subject Distance" in EXIF data

micloi

micloi

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Michael
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Just noticed in my exif data a field called "Subject Distance" which I found very interesting.

Does anyone know how this is calculated and how accurate it is?
 
I do not know how it is calculated, but I would be interested if any one does....

I have seen values reported in several other peoples EXIF data - but in my own shots, the "Subject Distance" is not always included in the EXIF data, but if present it's '0'.
 
Have you tried a tape measure to confirm it, do this on several test shots and let us know the outcome.
 
Tried in only 1 shot in the garden. It reported 7.11 meters and a rough measure of the distance gave me 7m so it seemed to be pretty accurate.

Will try a lager distance when it stops raining and can get the 400mm out in the street, my garden is not that long !!!

Wanted to see if other people had any experience on this.
 
It's just based off the position of the lens focus ring - It's used in ETTL-II modes as an additional calculation for the flash exposure - Do you have any lenses that don't have ETTL-II compatibility? You could try those and I expect there to be an empty Distance box in the EXIF.

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adsayer said:
It's just based off the position of the lens focus ring - It's used in ETTL-II modes as an additional calculation for the flash exposure - Do you have any lenses that don't have ETTL-II compatibility? You could try those and I expect there to be an empty Distance box in the EXIF.

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Thanks for the input!
So, if that is the case, and you get the focus right, it should be quite precise, it is good to know and very interesting for bird shots.
 
I'm not sure how precise it would be at birding distances dude... The accuracy will certainly be pretty good for short distances (mainly to do with the inverse square law of light exposure, where getting the distance/flash exposure correct is fairly critical) but I suspect it'll decrease as distance increases... a sort of % error. To be honest I'm surprised it's given a value with 2 decimal points of precision at ~7m for your test EXIF... can I ask what lens were you using?
 
I was using a Canon 400mm f/2.8 IS

Tried another shot to my bird feeder and got 9.76m. Measuring the distance I got around 10m (had to use the measuring tape a few times as it is not 10m long so cannot be exact) so the calculation sounds about right.
 
micloi said:
I was using a Canon 400mm f/2.8 IS

Tried another shot to my bird feeder and got 9.76m. Measuring the distance I got around 10m (had to use the measuring tape a few times as it is not 10m long so cannot be exact) so the calculation sounds about right.
Click to expand...

ooo so the shorter end then... as you said earlier, it'd be interesting to see how the values come out over much longer distances... can you update the thread when you do?
 
FWIW, I'm fairly sure not all Canon lenses report this parameter. DXO use it in some of their more advanced lens correction routines where it's available.
 
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Looked at some birds I took last week at a natural reserve.
Although I cannot be sure about the exact distances, what the field reposts seems to be a very good approximation of what I would perceive the distance to be (I have files that repost between 3.1m (damselfly) to just over 60m!)

For a more exact test though I will have to go out, measure a distance and take a shot.

Any tips on how I can measure long distances easily (20 to 50m) as my 3m tape will not work in this case? ... ;)
 
micloi said:
Any tips on how I can measure long distances easily (20 to 50m) as my 3m tape will not work in this case? ... ;)
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A 20 or 30 meter tape perhaps :thinking: :lol:

So how does it measure to target without without IR feedback? I am behind the times though.

micloi said:
My wife's Sigma 150-500mm also reported it and made a lovely cappuccino to boot :D
Click to expand...
I'm sold, bank card in hand :thumbs:
 
micloi said:
Looked at some birds I took last week at a natural reserve.
Although I cannot be sure about the exact distances, what the field reposts seems to be a very good approximation of what I would perceive the distance to be (I have files that repost between 3.1m (damselfly) to just over 60m!)

For a more exact test though I will have to go out, measure a distance and take a shot.

Any tips on how I can measure long distances easily (20 to 50m) as my 3m tape will not work in this case? ... ;)
Click to expand...

Howabout one of those golf rangefinder things don't know how acurate they are though
 
To my mind it must be calculating the distance using the autofocus data.
Thinking about it in reverse, focusing on an object then reading off a distance scale was exactly how older range finders worked
 
The following lenses will return distance info to the body

EF 14/2.8L USM
EF 20/2.8 USM
EF 24/1.4L USM
EF 28/1.8 USM
EF 35/1.4L USM
EF 50/1.2L USM
EF-S 60/2.8 USM macro
MP-E 65/2.8 1-5x Macro
EF 85/1.2 II L
EF 85/1.8 USM
EF 100/2 USM
EF 100/2.8 Macro USM
EF 135/2L USM
EF 180/3.5L Macro USM
EF 200/2.0L IS USM
EF 200/2.8L II USM
EF 300/2.8L IS USM
EF 300/4L IS USM
EF 400/2.8L IS USM
EF 400/4 DO IS USM
EF 400/5.6L USM
EF 500/4L IS USM
EF 600/4L IS USM
EF 1200/5.6L USM
EF-S 10-22/3.5-4.5 USM
EF 16-35/2.8L USM
EF 17-40/4L USM
EF-S 17-55/2.8 IS USM
EF-S 17-85/4-5.6 IS USM
EF-S 18-55/3.5-5.6 USM
EF-S 18-55/3.5-5.6
EF-S 18-55/3.5-5.6 II
EF-S 18-55/3.5-5.6 IS
EF 20-35/3.5-4.5 USM
EF 24-70/2.8L USM
EF 24-85/3.5-4.5 USM
EF 24-105/4L IS USM
EF 28-105/3.5-4.5 II USM
EF 28-105/4-5.6 USM
EF 28-105/4-5.6
EF 28-135/3.5-5.6 IS USM
EF 28-200/3.5-5.6 USM
EF 28-300/3.5-5.6L IS USM
EF-S 55-250/4-5.6 IS
EF 70-200/2.8L IS USM
EF 70-200/2.8L USM
EF 70-200/4L USM
EF 70-300/4.5-5.6 DO IS USM
EF 70-300/4-5.6 IS USM
EF 90-300/4.5-5.6 USM
EF 90-300/4.5-5.6
EF 100-300/4.5-5.6 USM
EF 100-400/4.5-5.6L IS USM

Out if production lenses with the same facility
EF 17-35/2.8L USM
EF 35-135/4-5.6 USM
EF 70-210/3.5-4.5 USM
EF 28-200/3.5-5.6
EF 28-70/2.8L USM
EF 28-80/3.5-5.6 USM
EF 28-105/3.5-4.5 USM
EF 100/2.8 Macro
EF 200/2.8L USM
EF 300/4L USM

Bob
 
I have just fired off a couple of shots using several lenses that should return the Subject distance information on a 7D but the subject distance is showing O on all lenses in the EXIF data.

Have I inadvertently somehow shut off this function?
 
I was about to check as I had it in Lightroom 3.0 but it appears to have been dropped form LR3.2. Certainly got the information previously on my 1DIV with 70-200 f/2.8L IS

Paul
 
I was amazed last week to see how much EXIF data Flickr calls up, some of my shots even had "camera temperature".

D
 
Does this only show on specific cameras or is it just down to the lens.
 
dinners said:
Does this only show on specific cameras or is it just down to the lens.
Click to expand...

"Canon Bob" listed above the lenses that return the subject distance, but I then believe its down to what software you are using to view the EXIF data.

I checked a few EXIF viewers and for example Canon's DPP & Zoom Browser / Opanda Iexif / Photoshop CS3 do not show the Subject Distance field at all, whereas IrfanView / ExifPro shows it, both with a Subject distance of Zero for a 7D with lenses that are supposed to return this information parameter.
 
Saw the list of lenses - just wondered if that was regardless of the body.

Cheers for the info the viewers though - will have to have a play to see if / where it shows.
 
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