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focus distance in EXIF

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bartman View Drop Down
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Post Options Post Options   Quote bartman Quote  Post ReplyReply Direct Link To This Post Topic: focus distance in EXIF
    Posted: 22 March 2011 at 21:27
Isn't it that modern lenses provide the focus distance to the camera (for ADI flash)? Why is that information not found in the EXIF information? Or is it, but I did not find it.

Bart
 



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sybersitizen View Drop Down
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 22 March 2011 at 21:39
Distance data was recorded in the KM5D/7D files, though very few programs could display it. I don't know about Sony files - apparently not even Sony's PMB shows it.
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Post Options Post Options   Quote kiklop Quote  Post ReplyReply Direct Link To This Post Posted: 22 March 2011 at 22:36
sybersitizen is right; it is only up to Sony to make this info available (it is present in the data .. no doubt about it, but so far i don't think anyone has been able to decrypt that part of the Sony makernote).
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Post Options Post Options   Quote analytical Quote  Post ReplyReply Direct Link To This Post Posted: 22 March 2011 at 23:34
ADI is useful only at relatively short distances because it exists solely to provide information for flash exposure. Anything beyond 5 meters or so is infinity so far as ADI requirement is concerned. Flash exposure distance doesn't have to be as precise as focus, so it probably isn't.    ADI likely will give no better measure of focus distance than inspecting the image.

ADI might not function at all unless ADI flash mode is selected in menu. Even if ADI is selected, it might not function when no flash is used.
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Post Options Post Options   Quote mikebr Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 00:27
It would appear that Sony do not add this information to the Exif data - at least they don't on the A700 and A900.

There is space for this information in the Exif 2.1 specification at tag location 37382
Ref JEIDA Exif Specification - see Page 35

One freeware Exif viewer/editor that displays this data is PhotoME which shows the subject distance for the sample photo provided, (taken with a D80) but does not show this information for either of my Sonys.

Edited by mikebr - 23 March 2011 at 12:00
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 03:41
Originally posted by analytical analytical wrote:

ADI is useful only at relatively short distances because it exists solely to provide information for flash exposure...

ADI is not the only reason why distance data is important. According to Sony it's also used in AS/SSS: 'Highly accurate image sensor shifting is achieved by analyzing input from two gyroscopic motion sensors, an IC chip (focal length) and distance encoder (subject distance) in the lens, and a high-sensitivity Hall device that monitors image sensor position.' Since it's being monitored, it makes sense that it would be recorded in the metadata.
 



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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 03:45
Originally posted by mikebr mikebr wrote:

One freeware Exif viewer/editor that displays this data is PhotoME which shows the subject distance for the sample photo provided, (taken with a D80) but does not show this information for either of my Sonys.

But that's not a definitive test. PhotoME also fails to display the distance data recorded in KM5D/7D files; but Dalifer - a program developed specifically to read those files - does show it.
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Post Options Post Options   Quote analytical Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 03:58
Originally posted by sybersitizen sybersitizen wrote:

Originally posted by analytical analytical wrote:

ADI is useful only at relatively short distances because it exists solely to provide information for flash exposure...

ADI is not the only reason why distance data is important. According to Sony it's also used in AS/SSS: 'Highly accurate image sensor shifting is achieved by analyzing input from two gyroscopic motion sensors, an IC chip (focal length) and distance encoder (subject distance) in the lens, and a high-sensitivity Hall device that monitors image sensor position.' Since it's being monitored, it makes sense that it would be recorded in the metadata.


Please cite the source of this information. Neither the owners' nor the service manual nor various catalogs and brochures for the A700 or lenses say this. In fact they say what I said. ADI is only mentioned referring to flash exposure.


Edited by analytical - 23 March 2011 at 04:11
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Post Options Post Options   Quote mikebr Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 07:08
@sybersitizen What operating system are you using? I downloaded Dalifer but it didn't work properly - it doesn't integrate with windows explorer to show the additional Dalifer tab when right clicking and selecting properties.
Also the Dalifer viewer works with .jpg files but not with .arw files
I'm running Win 7 64bit
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Post Options Post Options   Quote pnaciona Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 07:31
Originally posted by analytical analytical wrote:

Originally posted by sybersitizen sybersitizen wrote:

Originally posted by analytical analytical wrote:

ADI is useful only at relatively short distances because it exists solely to provide information for flash exposure...

ADI is not the only reason why distance data is important. According to Sony it's also used in AS/SSS: 'Highly accurate image sensor shifting is achieved by analyzing input from two gyroscopic motion sensors, an IC chip (focal length) and distance encoder (subject distance) in the lens, and a high-sensitivity Hall device that monitors image sensor position.' Since it's being monitored, it makes sense that it would be recorded in the metadata.


Please cite the source of this information. Neither the owners' nor the service manual nor various catalogs and brochures for the A700 or lenses say this. In fact they say what I said. ADI is only mentioned referring to flash exposure.

Here, let me help you with that... It's from Konica Minolta, not Sony, but I'm sure you'll agree that it's the same technology as SSS. Anyway, look for the section "Effective at any focal length":
http://ca.konicaminolta.com/products/consumer/digital_camera/slr/dynax-7d/02.html

I think you've misread sybersitizen's statement. He didn't say ADI is used in AS/SSS. He used the word "distance". ADI flash metering is one Minolta/KM/Sony technology that uses distance. AS/SSS uses distance information too but not ADI.

Anyway, I think all Minolta AF lenses can report distances regardless of ADI capability but I don't know that for sure.

Edited by pnaciona - 23 March 2011 at 07:47
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Post Options Post Options   Quote bartman Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 09:19
Thank you all for elaborating on my question. I posted it just for curiosity; I like to know how things work. From my part, I don't know why I should know the focus distance of a photo.
Originally posted by pnaciona pnaciona wrote:

Anyway, I think all Minolta AF lenses can report distances regardless of ADI capability but I don't know that for sure.

But old Minolta AF lenses have only 5 contactpoints. I thought that the three extra contactpoint of new lenses are for the distance information.

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Post Options Post Options   Quote kiklop Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 11:01
Originally posted by analytical analytical wrote:


Please cite the source of this information. Neither the owners' nor the service manual nor various catalogs and brochures for the A700 or lenses say this. In fact they say what I said. ADI is only mentioned referring to flash exposure.


That's one of the problem with a system-userbase not having highly regarded and knowledgeable persons like Thom Hogan is for Nikon for example; there is a lot of info about our gear that is unknown to the public or the info is getting lost with time (we have similar discussions in the past and i was writing about it) .

Anyway, back to to topic; subject distance is indeed part of the AS/SS system. It is logical to be so and personally i got this info from various sources inside Sony. Yes, it isn't in the user manual and you won't find this statement anywhere officially released by Sony AFAIK... except in one place; Alpha lens book that Sony released few years ago.

On pages 118-119 there is a short technical explanation of how SS works and among other things it states:

"system (SS) accuracy is also enhanced by focal length and shooting distance data feedback from the lens ..:"
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Post Options Post Options   Quote kiklop Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 11:07
Originally posted by mikebr mikebr wrote:


Also the Dalifer viewer works with .jpg files but not with .arw files
I'm running Win 7 64bit


Unfortunately, Dalifer is pretty much outdated software not updated to read arw maker note properly.
And subject distance info was something Dalibor (the author of Dalifer) was working on in the last stage of dalifer development and he didn't completed this part of the code. But he did succeed in tracking the chunk of mrw makernote that is carrying this info as can be read here

Unfortunately, nobody followed his work :(

Edited by Kiklop - 23 March 2011 at 11:09
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Post Options Post Options   Quote kiklop Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2011 at 11:19
Originally posted by bartman bartman wrote:


But old Minolta AF lenses have only 5 contactpoints. I thought that the three extra contactpoint of new lenses are for the distance information.


If you follow discussions at the the link i gave above you will get additional info about D and older lenses. In short, older (non d lenses) do forward subject distance info to the camera as well but this info is more accurate with "ADI chip" and doesn't get lost in certain scenarios (manual focus)
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