Secrets of the blue dot revealed! (and other M8 metadata)

[sdai]

The CCD board variance must be very trivial ... it could be a driver update due to the change of the controller chip in the chassis.

[yeungkeefu]

Great work and thanks for sharing.

Keith

[luigi bertolotti]

Gave a quick look... sufficient to say "GREAT !" to our friend Carl ; together with Mark's exceptional work & pics on the M8 disassembled, it stands as a document to save with care and be studied in depth.

[marknorton]

Originally Posted by sdai

The CCD board variance must be very trivial ... it could be a driver update due to the change of the controller chip in the chassis.

Simon, I think you're right, the same components imbedded in the UPD file are installed whatever the hardware versions.

At most, there may be detailed logic or hardware setup changes such as:

If CCD_BoardID <= 2 Then Do_This Else Do_That

[chris_tribble]

Carl - many thanks!

Do any of you really clever people out there think that there's a way of getting aperture and lens information across to Lightroom... or will it pick up the information from the exif that CF re-writes during a batch process? Just tried to do this with a small set of files - but LR still shows Leica lenses as "unknown" - an annoyance.

Grateful if any of you have thoughts...

[sandymc]

Originally Posted by chris_tribble

Carl - many thanks!

Do any of you really clever people out there think that there's a way of getting aperture and lens information across to Lightroom... or will it pick up the information from the exif that CF re-writes during a batch process? Just tried to do this with a small set of files - but LR still shows Leica lenses as "unknown" - an annoyance.

Grateful if any of you have thoughts...

Chris,

If you run the images through CornerFix 0.9.1.6 with the "Update EXIF" option enabled the "Lens" information should show, and the aperture should show under "Exposure". But you have to enable the "Update EXIF". It's disabled by default.

Sandy

[asfeir]

Thank you for such a detailed and thorough work.
I do not know if I missed anything, but will maker notes be affected by Adobe DNG converter? You mentioned a number of problem under the heading "Maker notes safety", but Adobe DNG converter is not included.

Again, thanks

[Paul_S]

Great job, many thanks to Carl, Scott and Sandy.
I did a quick scan of the PDF, will be happy to spent more time with it.

[chris_tribble]

Sandy - got this - thanks. The issue then is that CF (sensibly) creates a copy rather than over-writing the original DNG. My problem is that I rarely need to use CF as my wide lenses coded + I have IR cut filters on all lenses... What I would love to be able to do is to run a batch across gigabytes of files adding the exif data to Leica files ... creating copies would clearly not do the job.

I suppose what I'm asking for is something that CF isn't designed to do - so please don't take this as a criticism of an outstandingly good piece of work ... still looks as if I'm going to have to live with unknown lenses in LR unless I can put enough pressure on the LR developers to treat Leica users as well as they treat owners of Canon systems...

Many thanks

[sandymc]

Originally Posted by chris_tribble

The issue then is that CF (sensibly) creates a copy rather than over-writing the original DNG. My problem is that I rarely need to use CF as my wide lenses coded + I have IR cut filters on all lenses... What I would love to be able to do is to run a batch across gigabytes of files adding the exif data to Leica files ... creating copies would clearly not do the job.

Chris,

Yes, that's correct - CornerFix will not overwrite original files in batch mode - a safety feature. One possible work around might be to convert with CornerFix in batch mode, then use a batch renaming tool - there are a lot around - to convert back to the original filename. Pretty much any batch renaming tool should be able to handle removing a trailing _CF

Sandy

[c6gowin]

Originally Posted by Mark_Schretlen

So when the Summarit is set at f/11, the G-stop estimates it at f/18? Even though it is off by almost two stops, I still think it is better than Leica's current method of reporting an f/11 f-stop as f/2.5 in the EXIF.

Yes, you are correct. In my very limited trial of the EFIX update feature in Corner Fix, the reported g-stop was shifted about 2 stops from the actual f-stop in all photos except one where the shift was less than 2 stops. Perhaps in the future it will be possible to better predict the behavior of the blue dot and g-stop estimate under different conditions as the M8 community gains more experience using this new EFIX update feature in Corner Fix. (thank you again Carl, Sandy, and Scott).

I think most of us wished Leica had provided an accurate method to report aperture in the EFIX data. However, based on Carl's paper and design limitations inherent in M lenses it is understandable to see why Leica chose not to use the f-stop estimate provided by the blue dot. I am sure the M8 community would be screaming at Leica if they had reported the f-stop in EFIX with the inaccuracy I saw in my limited trial. The M8 community is fortunate to have talented people who are able to provide features/fixes that may not fit the confines of a corporation. Grass roots efforts such as this are not met with the same expectations and liabilities as if it came from a corporation.

[scott kirkpatrick]

Originally Posted by c6gowin

Out of curiosity, I ran Corner Fix in batch mode to update the EXIF data only (no lens profile loaded) for the set of 75mm Summarit lens resolution test photos I posted earlier today. The updated EXIF correctly identifies the Summarit lens but the reported G-stop is incorrect. The reported G-stop was 4.7 for an actual f-stop of 2.5 and incremented essentially relative to the actual f-stop as it was stopped down for the lens test. The G-stop inaccuracy for my test photos could be due to the 75mm focal length versus the theorized blue dot fov as discussed in the paper. Of course there are many other variables that could have caused the offset in G-stop versus f-stop.

Summarit tests are rare still. I just rechecked some CV21 and Summicron 35 asph shots using the latest .6 release of CornerFix and got the following results:

CV21: actual f/8 Leica 11.3 Sandy 8.0

35/2 asph actual f/8 Leica 9.5 Sandy 8.0
" actual 5.6 Leica 6.7 Sandy 5.7
" actual 2.0 Leica 2.4 Sandy 2.0

This is consistent with all of Carl's data. Maybe the Summarits do something unexpected. Try some more, with "normal" lighting -- a wide scene, not backlit, and see if you still get such big errors.

scott

[c6gowin]

Scott, I definitely plan to run Coner Fix to update the EFIX data on photos other than the Summarit. I chose the Summarit lens tets photos as a trial simply because I kept good notes on the actual f-stop.

[cbretteville]

Thank you for your kind words all. I really appreciate it. It has been a lot of work so I'm glad it is of interest.

- Carl

[cbretteville]

Originally Posted by asfeir

I do not know if I missed anything, but will maker notes be affected by Adobe DNG converter? You mentioned a number of problem under the heading "Maker notes safety", but Adobe DNG converter is not included.

Abudi,
The list in the paper is by no means an exhaustive one. I had not considered the DNG converter so I had to test it. Turned out I had to do a little work on my decoder to be able to read all the metadata in the converted files.

As I expected, it does not save the maker notes. The DNG Converter follows the DNG specification (I'm glad Adobe takes it's own medicine) and ignores the maker notes when it writes the converted file.

Yet another reason for Leica to add this tag to the files.

- Carl

Edit: Hold the phone! It seems I may be wrong. There are indicators that make me think the maker notes block is saved as "DNG Private Data". I will need to investigate this further and report back.

[cbretteville]

Originally Posted by scott kirkpatrick

iMaybe the Summarits do something unexpected. Try some more, with "normal" lighting -- a wide scene, not backlit, and see if you still get such big errors.

I can't see how the Summarits differ from any other. The only thing I can think of is that Leica has messed up when adding the lens specific info in the lens table in v1.110. This should be easily testable by switching lens detection off and shoot using a middle aperture, f5.6 to f8.

- Carl

[scho]

Originally Posted by scott kirkpatrick

Summarit tests are rare still. I just rechecked some CV21 and Summicron 35 asph shots using the latest .6 release of CornerFix and got the following results:

CV21: actual f/8 Leica 11.3 Sandy 8.0

35/2 asph actual f/8 Leica 9.5 Sandy 8.0
" actual 5.6 Leica 6.7 Sandy 5.7
" actual 2.0 Leica 2.4 Sandy 2.0

This is consistent with all of Carl's data. Maybe the Summarits do something unexpected. Try some more, with "normal" lighting -- a wide scene, not backlit, and see if you still get such big errors.

scott

I'll do some more testing with my CV and Zeiss lenses, but so far the trend I'm seeing is just the opposite - Leica f stop values are closer to actual than CF f stops, which tend to consistently report f stops values lower (wider opening) than actual. Is there a way of having the Leica values reported in exif, rather than the CF estimates?

[scho]

Originally Posted by scho

I'll do some more testing with my CV and Zeiss lenses, but so far the trend I'm seeing is just the opposite - Leica f stop values are closer to actual than CF f stops, which tend to consistently report f stops values lower (wider opening) than actual. Is there a way of having the Leica values reported in exif, rather than the CF estimates?

Example with CV 28mm f/3.5 lens. Aperture values are in the following order: actual aperture, leica estimated aperture, cornerfix estimated aperture. All data taken from the CF log window after processing each shot.

3.5, 3.4, 2.8
5.6, 5.7, 4.8,
8, 8.0, 6.7
11, 11.3, 9.5

[sandymc]

Originally Posted by scho

Is there a way of having the Leica values reported in exif, rather than the CF estimates?

Not in the current version. If many people have the same experience as you do however, an option could certainly be added in the next version of CornerFix.

Sandy

[guidomo]

Just an idea.

I could imagine that big lenses or lenses with large hoods tend to shade the blue dot somewhat. In this case, wouldn't the camera tend to underestimate the f-stop? (Thinking there was less ambient light than there really is, it would think the lens is wider open than it really is).

I guess all I am trying to say is that there may be a relationship between lens geometry and quality of f-stop estimate. But I do realise they have set the blue dot as high as possible to minimise this effect. And that would hardly be something one could possibly correct for.