A question to Canon re. focusing distance in EXIF

[Nicolas Claris]

Bonjour Chuck
my turn to welcome you here. I've read you a lot before on another forum.
I use a 1DSMII mostly with L Canon lenses except for ultrawide.

BTW If you have any info on if/when Canon will launch a prime lense between, say 12 and 18mm, do not hesitate to inform us, we're a lot to wait for it!

My concern today is that I use DXO software to devellop some of may raw files (mostly the shot done in interior of yachts) to correct some distortion as well as "piqué".
This software needs to read the distance of focusing info in the EXIF. Otherwise I have to enter it manually, and this is of course not very precise.
This info is not written in the EXIF produced by the camera.

Would that be difficult to add within a new firmware? Is this already planned?
Do you have any information to give us in this regard?

Thank you for reading me and my far-from-perfect English.

Very best regards

[Michael Tapes]

Nicolas,

As fellow admin, I must be fair to all, and also ask that we do not address chuck directly in our posts. That was the RG policy and I think we should follow. (wow, that was weird)..

perhaps I can shed some light on the subject in the meantime. Not all Canon lenses make the shooting distance available to the camera. In previous cases this was the cause of the distance field not being filled or being empty or wrong.

Can you check to see if this is lenes dependant, or if it is across the board.

HTH.

We still friends? :>)

[Doug Kerr]

Hi, Michael,

Not all Canon lenses make the shooting distance available to the camera. In previous cases this was the cause of the distance field not being filled or being empty or wrong.

It was always my understanding that whether or not the lens fed distance information to the camera (for example, to be used in coinnection with E-TTL II flash metering), the distance information placed in the Exif metadata was (almost?) always meanigless.

Perhaps others here know something different about this.

To Nicolas: How does DxO use the focus distance? I know of course that it requires the focal length of the lens (which is reliably found in the Exif metadata).

[Nicolas Claris]

Nicolas,

As fellow admin, I must be fair to all, and also ask that we do not address chuck directly in our posts. That was the RG policy and I think we should follow. (wow, that was weird)..

perhaps I can shed some light on the subject in the meantime. Not all Canon lenses make the shooting distance available to the camera. In previous cases this was the cause of the distance field not being filled or being empty or wrong.

Can you check to see if this is lenes dependant, or if it is across the board.

HTH.

We still friends? :>)
Mon ami Michael
Of course we're still friends, One of the good reasons (there are plenty others, but shhhhhh...) is that I just see now your post!
Anyway I understand your remark but do not feel guilty as my post and questions were/are directly toward Canon in order to know if this could be in an upcoming new firmware, who else than CW could answer?
My question is really objective without any incorrect means. On the contrary!
I still hope that CW will have a minute to enlight us on this subject...
And if this was weird at RG why should we stay on this.
My opinion is that if posts are correct and polite why shouldn't we post to whoever, I've seen on another forum someone asking about cameras to be brought in a marine atmosphere, and someone did suggest to contact me, here. I would of course answer and wouldn't feel personnaly attacked by a direct question...

:-) - :-) - :-) - :-) - :-) - :-)

[Doug Kerr]

Hi, Nicolas,

Perhaps it's the old taboo about mentioning the name of the deity.

Would asterisks help, as in "J*h*v*h"?

Now how does this work? Can we hail you, but not Chuck Westfall?

Best regards,

Doug

[Nicolas Claris]

Not all Canon lenses make the shooting distance available to the camera. In previous cases this was the cause of the distance field not being filled or being empty or wrong.
Can you check to see if this is lenes dependant, or if it is across the board.

I've checked and DXO can't get this info with the following lenses:
EF24-70mm f/2.8L USM
EF400mm f/5.6L USM
EF70-200mm f/2.8L IS USM
and Sigma 12-24 as well
good question, but bad answer!

[Nicolas Claris]

To Nicolas: How does DxO use the focus distance? I know of course that it requires the focal length of the lens (which is reliably found in the Exif metadata).
Hi Doug
I know it needs it but I really don't know how, I only know it needs this info for "piqué" as well as lense corrections. (http://dxo.com/en/photo/support/form_pb_known_problems.php#q7
When DXO can't find this info, you may enter it manually, but as you have to guess it is far from accurate! (http://dxo.com/en/photo/support/form_tips_n_tricks.php#q1

BTW I have never seen distance info (bad or reliable) in the Exif metadata.

Cheers

[Alan T. Price]

DxO Optics Pro is based on data from lens tests made at various focus distances as well as various apertures and focal lengths. If it can it uses the distance data to access the most appropriate test results and fiddle your image accordingly. For those who don't know, the software fixes all manner of distortion, vignetting and other problems associated with particular lens/camera combinations. The alternative PT Lens tests are I believe only done at one focus distance (infinity).

[Chuck Westfall(Canon USA)]

Hi, Nicolas et al:

Here are some obaservations on the topic of distance information in Exif data from EOS digital SLRs:

1) Most but not all current Canon EF lenses report distance data to the camera. The lens specification charts we've published since 2004 usually indicate which lenses support distance data. However, these are not comprehensive lists, because they typically do not contain information about discontinued lenses. I would be happy to provide a current listing, but I'm not sure if this forum provides a good way to publish it. Perhaps Asher K. or Michael T. could comment.

2) To the best of my knowledge, none of the current EOS digital SLRs records distance information in Exif data, even with lenses that support it. Most likely this is because our current software applications like DPP, RIT, etc., don't use it.

3) I understand that some 3rd-party software applications like DxO do use this information. Several users have requested that distance information should be restored to the Exif data generated by our cameras, in order to support these 3rd-party applications. We have forwarded these requests to Canon Inc. via our monthly reports, but so far there is no indication that these requests will be granted. If anything changes on this subject, I will let you know.

Best Regards,

Chuck Westfall
Director/Media & Customer Relationship
Camera Marketing Group/Canon U.S.A., Inc.

[Doug Kerr]

Hi, Nicolas,

Thanks.

Best regards,

Doug

[Jack Joseph Jr.]

Doug, you are the best! Why don't we settle on CWFL as the tetragrammaton signifying the unmentionable diety in this case.

[Nicolas Claris]

Thank you very much Chuck for your clear answer, I hope that Canon will here you! That would help us a lot especially when doing big enlargement as these:http://www.claris.fr/Diaporama_EXPO_DUPON/index.htm

[Michael Tapes]

I would be happy to provide a current listing, but I'm not sure if this forum provides a good way to publish it.

Hi Chuck,

Thanks for all of the great information that you provide. Please send the listing to me and I will make sure that we provide a link. Thanks...

[Michael Tapes]

Why don't we settle on CWFL as the tetragrammaton signifying the unmentionable diety in this case.


Everyone.....

I am not trying to be a hard ass. It is my opinion that we should post for information on Canon issues, and anyone who knows the answer or can provide info should do so.

Since we know that Chuck Westfall (there, *I* said it!) is monitoring this forum (thanks so much Chuck!) I see no need to address Canon issues to him. He will respond when and where he can and where only he can provide the proper information. I just think it unfair to him to direct specific questions to him, sort of forcing a reply. Eventually every question could be directed to him. So lets keep the forum what it is designed to be, that being a peer to peer forum, with people of great expertise either moderating or participating.

That is my opinion. I will discuss with Chuck and get his opinion.

Thanks to all for your participation in the forum!

[Doug Kerr]

Hi, Michael,

Well said.

Best regards,

Doug

[Sean DeMerchant]

How does DxO use the focus distance? I know of course that it requires the focal length of the lens (which is reliably found in the Exif metadata).

If I had to hazard a guess, I would guess the the PSF (Point Spread Function) (http://citeseer.ist.psu.edu/cis?q=psf&submit=Search+Documents&cs=1) of an optical system is affected by the chosen focal distance. Hence, this additional data would help increase the accuracy of the correction.

But without direct knowledge of the optical modeling done by DxO, I can hazard a guess at what I would measure to write such a tool.

enjoy,

Sean

[Doug Kerr]

Hi, Sean,

Makes sense to me.

Best regards,

Doug

[Bart_van_der_Wolf]

If I had to hazard a guess, I would guess the the PSF (Point Spread Function) (http://citeseer.ist.psu.edu/cis?q=psf&submit=Search+Documents&cs=1) of an optical system is affected by the chosen focal distance. Hence, this additional data would help increase the accuracy of the correction.

Yes, that is very likely why that parameter is used. Afterall, in the most simple of designs, focussing at a shorter distance requiring to extend the distance from lens to focal plane, results in using a smaller part of the image circle (and magnification of center aberrations). In more complicated internal focusing sytems, who knows what happens optically?

Bart

[Jan Luursema]

2) To the best of my knowledge, none of the current EOS digital SLRs records distance information in Exif data, even with lenses that support it. Most likely this is because our current software applications like DPP, RIT, etc., don't use it.


Wow that's weird, I always thought it did. But now I see with my 20D the distance info is not there!
With my former 300D the info indeed was there. Why would the Canon software engineers remove it from the firmware? It's not like it's a disadvantage I would think.

[Chuck Westfall(Canon USA)]

The R&D engineers haven't commented on their reasoning, so we can only speculate that they felt it wasn't necessary to include the information if it wasn't being used by Canon software.

Best Regards,

Chuck Westfall
Director/Media & Customer Relationship
Camera Marketing Group/Canon U.S.A., Inc.

[John_Schwaller]

DxO Optics Pro is based on data from lens tests made at various focus distances as well as various apertures and focal lengths. If it can it uses the distance data to access the most appropriate test results and fiddle your image accordingly. For those who don't know, the software fixes all manner of distortion, vignetting and other problems associated with particular lens/camera combinations. The alternative PT Lens tests are I believe only done at one focus distance (infinity).

I am not sure if PTLens use "infinity" as the setting. It does lens correction very well for most normal distance...from reasonably close in out to infinity....and it's price is VERY resonable.

PTLens' main weakness is very close distances. DxO does, as I remember, do their analysis and correction based on 3 distance "bands", so it's correction capability is better closer in.

I did some tests on these "back when" and no longer have the results, but the added ability, for me, was not worth the large cost, particularly since DxO classes the 5D in the "Pro" pricing grid.

Both PTLens and DxO will do vignetting correction. However, I prefer to correct this on the RAW image in ACR. This allows me to then batch the output (for posting on my personal family website) using first PTLens, then Noise Ninja and Focal Blade.

BTW....Canon did provide focal distance info in earlier EOS digitals. I don't remember at this time, but I beleive the 10D, D30, D60's may have. However, it appears they deliberately stopped doing such with the 20D, 350D, 1D, etc. I doubt they will add it back....and, I suspect, Doug Kerr is correct, that it was not necessarily accurate for the purpose of DxO. Actually guessing the band is not to bad, except it keeps one from being able to batch process.

John

[Anita Saunders]

BTW If you have any info on if/when Canon will launch a prime lense between, say 12 and 18mm, do not hesitate to inform us, we're a lot to wait for it!

There is of course the 15mm fisheye, but alas no exif info re focus distance. A useful snippet to add when considering post process corrective filters or formulas. I guess it's another 'stick it on the wish list'. ;)

[Anita Saunders]

BTW....Canon did provide focal distance info in earlier EOS digitals. I don't remember at this time, but I beleive the 10D, D30, D60's may have. However, it appears they deliberately stopped doing such with the 20D, 350D, 1D, etc. I doubt they will add it back....John
I just checked an old exif file from my D60 - 15mm was recorded under a 'focal length' field, however the 'lens' field was left blank. Not therefore an actual focus distance.

In a more recent 5D exif file, both 'focal length' and 'lens' field say 15mm but still no 'focussing distance'.

[Bart Hazes]

Dear all,

I'm just new to this list (my home base is wetpixel an underwater photography forum) but I have a canon camera question that members of wetpixel said would be best addressed to Chuck Westfall. Using google I found that my main question had already been answered here on OPF. Actually it is a pity I didn't find the open photograph forum earlier since it clearly has a lot of good and detailed information. So thanks for providing this resource.

My question/comment is that for me the distance information in EXIF is very important to use the camera as a measuring device. Basically, I want to add a scale bar to my images and write a program where users can click on two points and the program will report the real-world distance between those two points. Obviously, the scale bar will only be accurate in the plane of focus but by using a large aperture (relative to the magnification) the shallow DOF should take care of that.

As an end-user it is very hard to understand why Canon has stopped making this information available (the 10D still reports distance in EXIF) especially since competing brands do include the information. The DxO argument made on this forum is probably the strongest reason for Canon to include distance information; us underwater photographers are just too small a market to have much clout. But Canon has a reputation in scientific instrumentation and transforming their cameras into measurement devices, even if with only moderate precision, should be of more general interest.

Perhaps Canon is just protecting its reputation by taking an "If we can't do it perfectly we'd rather not do it at all" attitude. Or maybe they are afraid that people will use a diopter and not realize that the distance information is now plain wrong (at least I think it will be). Either way I still think Canon should make the information available and give some credit to the intelligence of their users to decide if and how to use the distance data.

So one more BIG VOTE for updating the firmware to show distance information in EXIF.

Bart Hazes

PS: I'm shooting with a Canon 20D but decided to post in this Canon Pro series forum because it fits with this ongoing discussion and it is really independent of which body you use.

[John Craig]

I wonder if this stopped showing in Exif around same time that A-DEP mode got removed from cameras -- would these be related?

Also, on a similar note, I put in a request that perhaps for future camera models, there could be an added functionality to get a focused distance readout on the LCD, and likewise also expected DOF for whatever aperture has been selected (obviously calculated by this distance, sensor size, and lens FL mounted). Wouldn't it be cool to be able to look at your camera, know that you're focused at 4.8 feet, and with your selected aperture, DOF will range from eg. 4.4 feet to 5.2 feet?

Obviously DOF is only a guideline with some built in presumptions.. but still I think could be really useful.

[Nicolas Claris]

Hi John
cool! that's a very great idea...

Also, on a similar note, I put in a request that perhaps for future camera models, there could be an added functionality to get a focused distance readout on the LCD, and likewise also expected DOF for whatever aperture has been selected (obviously calculated by this distance, sensor size, and lens FL mounted). Wouldn't it be cool to be able to look at your camera, know that you're focused at 4.8 feet, and with your selected aperture, DOF will range from eg. 4.4 feet to 5.2 feet?

Obviously DOF is only a guideline with some built in presumptions.. but still I think could be really useful.

[Ray West]

I have no idea why canon have stopped showing the focal distance, but there is no need for it to be known by the camera for it to operate successfully. The same for much of the information that is displayed, e.g. iso, speed, etc. I am not talking about manual settings, but just what the camera needs to function. If they give the distance as, say, 25 feet, how long before folk want it in fractions of an inch, and then start complaining that the indicated 25 ft is in fact 23 ft.

[Nill Toulme]

Hmmm... Isn't one of the main differences between e-ttl and e-ttl2 that the latter makes use of focus distance info provided by certain lenses? And wasn't Canon precluded for a long time from making use of focus distance info in their flash systems because of some patent conflict with another well-known camera manufacturer? And didn't focus distance info stop getting reported by the cameras at about the same time as e-ttl2 came out? And wasn't there a second shooter in Dallas in 1963?

Nill
~~
www.toulme.net

[Bart Hazes]

Interesting hypothesis Nill! The most plausable reason I've yet heard for Canon not to report the focus distance.

I wonder if Canon would be allowed to report the raw encoder value (or whatever means they use to determine the focus gear setting). Shouldn't be too hard to correlate those raw values to real focus distances. That would be good enough for me and I'm sure the DxO people would be smart enough to use that information as well.

Bart

[Bo-Ming Tong]

D30, D60 and Digital Rebel support EXIF distance info. But 1D does not seem to have it. Pretty odd given 1D was one of the older cameras, and it is supposed that older cameras have it but newer cameras don't. Or am I not using the correct exif reader? (I used a program called exiv2.)

[Joseph A. Kurkjian]

Hmmm... Isn't one of the main differences between e-ttl and e-ttl2 that the latter makes use of focus distance info provided by certain lenses? And wasn't Canon precluded for a long time from making use of focus distance info in their flash systems because of some patent conflict with another well-known camera manufacturer? And didn't focus distance info stop getting reported by the cameras at about the same time as e-ttl2 came out? And wasn't there a second shooter in Dallas in 1963?

Nill
~~
www.toulme.net

Wow, the old "second shooter" theory; yes there was at least one according to a LOT of technical analysis but they couldn't find a smoking gun(s). Maybe Canon engineers can't find the distance information (new theory but lacking juicy sub-plots)?

Regards,

Joe Kurkjian