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View Full Version : Distance to Subject in exif


Daveart
16th February 2013, 05:09 PM
Hi I have noticed the distance to subject in the exif, varies, I notice on 2 photos taken from the the same place and the subject remained in the same place came up with 2 differrent distances not by a small amount but by quit a lot like one came up with 2.6mtrs and the second said 3.8mtrs.

Has any one else noticed this?.

Dave

CJJE
2nd March 2013, 09:03 PM
Hi Dave,

Sorry about the delayed reply, but after checking some of my pics I cannot find any which show the distance between camera and subject! I presume this is being set by the lens knowing where it is focused, and perhaps this varied on your examples? But my EXIFs only quote the focal length of the lens and not where it focused. My pics were taken on my E-M5, Lumix G1 and Lumix GF2. Were you using a different camera for your EXIFs? Or are you using a different EXIF reader perhaps? (I have been checking mine using OPANDA IEXIF2 as I don't have Photoshop on this PC.)

Daveart
2nd March 2013, 09:13 PM
Hi and Thanks for commenting, it is in the exif within photoshop, it shows on the raw file, I took a couple photos using the 75mm lens from the same position at the same subject and recorded 2 different distances both were indoors and the room in total was 4 metres at the extremes and they were taken about half way the one images said 2.6 metres the other said it was 6.2 meters that would have been impossible. I just woundered if any one else noticed the discrepancy.

Dave

CJJE
2nd March 2013, 09:45 PM
Hi Dave,

I've just Googled for this and found a new EXIF viewer (free still) - the KUSO EXIF viewer which gives the depth of focus and focus distance for pics taken with my EM-5 (but not pics taken with my Lumixes). I presume it is reporting data from the lens captured by the camera. (I think the camera needs this info for flash exposures.) Interestingly my new EXIF viewer doesn't know which lens I've used (only its focal length and serial number!) while the OPANDA viewer tells me its a Lumix 12-35 etc!

Daveart
2nd March 2013, 09:55 PM
That is quite strange chris, I know that once I convert to jpeg it no longer appears in the jpeg exif file, but that could be photoshop removing it from the EXIF data as not required.

Who knows maybe Olympus could explain this.

Dave

CJJE
2nd March 2013, 10:12 PM
All the pics I've been looking at are JPGs (this PC doesn't have a RAW reader on it so the RAW images are on my main PC). So I'm able to see the EXIF data in the JPGs albeit differing parts depending on which EXIF viewer I use!

I'll have to check out what I see in Photoshop Elements tomorrow.

But to get back to your query, the focus distance must be based on where the lens has been set by the camera (I see that a Pentax forum reports that they see the distance in terms of "steps" rather than metres or feet.) The depth of focus and hyperfocal distance is interesting and I believe this is calculated from the aperture, focal length and focus distance. But all of the pics I've looked at seem to have consistent distances, and I can only think that a distance outside the length of a room suggests that the lens wasn't focused when the image was recorded?

Daveart
2nd March 2013, 10:17 PM
Hi again chris the image that had a distance further than the distance of the room was in perfect focus as it was at f1.8 so hyperfocal distance couldn't account for the being in focus.

peak4
2nd March 2013, 11:15 PM
I've found that the focal distance, as opposed to length, in exif is at best misleading and often gibberish. It's as though the gremlins have been making anagrams with the numbers.

It's not the easiest to use, but probably the most powerful exif viewer is Phil Harvey's ExifTool (http://www.sno.phy.queensu.ca/~phil/exiftool/) available as a stand alone or can be used from command line.
It can read, amend and add to the exif should you have the need, and is able to change the times if you've forgotten to reset the camera when you went half way round the world.

There's also a basic GUI for it available from HERE (http://freeweb.siol.net/hrastni3/foto/exif/exiftoolgui.htm)

CJJE
3rd March 2013, 12:31 PM
I've now been on my main PC and find that Photoshop Elements doesn't give this info in its EXIF reader for either JPGs or RAW files. So its not surprising that I hadn't seen this before.

OM USer
5th March 2013, 05:26 PM
I've downloaded exiftool and exiftoolgui and run them. Great.
I can see the focus distance under "FocusDistance" in the "MakerNotes" tab. Great.
But can anyone tell me where I might find the light level if indeed it is recorded (can't find this in Oly Viewer 2 either).