why digitally code lenses?

D

daniel buck

Established
Local time
11:16 AM
Joined
Jan 9, 2008
Messages
56
Maybe my google skills have been lacking lately, or maybe I'm just not seeing the obvious. Buy what is the reasons that one would want to digitally encode lenses?

At first, I thought it was just to have the correct EXIF data, which I don't really care about at all. I use manual lenses on my 1-series canon all the time, so I'm not used to geting full EXIF data, and I wouldn't have a use for it even if I did have full data on all my manual lenses.

But then as i was reading some reviews on some M-mount lenses lenses, I picked up that one reviewer said that they had better lens performance (corner sharpness and better CA, i believe it was?) once they digitally coded the lens.

So, does coding the lenses alter the images produced as well as the EXIF? Does this stand true when shooting RAW/DNG files, or only JPEG files? I rarely ever shoot JPEG files (can't remember the last time I did), so for someone who only shoots RAW (DNG), and doesn't care about EXIF data, is there any practical reason to code lenses?

Another thing to note, my M9 has is still in shipping, so maybe once It actually arrives and am using it, the answers will be more apparent. But right now in all my searching, I'm left with a little bit of a cloud infront of the answers.

Thanks for any thoughts on this!

Daniel
 
Apparently, in addition to add to the EXIF, the coding tells the camera what to expect with certain lenses. For instance, if wide angles tend to cause vignetting, the sensor will compensate for it, or increase contrast with lenses reputedly having low contrast, and so on.
 
so this would be something that would benefit someone who is shooting RAW/DNG files as well, right? More than just some processing done to JPEG files?
 
Thanks PKR, I just scanned quickly through that thread and the article, I don't see how that is related to digitally coding lenses? I will read it more thoroughly when I get home tonight. :)
 
Coding on both the M8 and M9 is needed for lenses of 35mm and wider to deal with the side-effects of the IR filters (front on M8, on-sensor on M9) unless you are ok using Cornerfix for all those shots. Those are compelling enough reasons for me, but otherwise, the coding seems to add very little other than EXIF data.

Also if you use AUTO-ISO and the lens is coded it will specify a slowest-speed default based on the 1/focal-length rule. Personally I've always liked to double that rule, so I don't use the feature.
 
Ben Z said:
Coding on both the M8 and M9 is needed for lenses of 35mm and wider to deal with the side-effects of the IR filters (front on M8, on-sensor on M9) unless you are ok using Cornerfix for all those shots. Those are compelling enough reasons for me, but otherwise, the coding seems to add very little other than EXIF data.

Also if you use AUTO-ISO and the lens is coded it will specify a slowest-speed default based on the 1/focal-length rule. Personally I've always liked to double that rule, so I don't use the feature.
Click to expand...


is this only for older lenses? Are newer lenses already coded? such as a Voigtlander 28/2.0 Ultron?
 
Last edited:
I think that if you set the lens in the M8/M9 menu then it will use processing for that lens. The digital encoding allows that to happen automatically without using the menu to set it. Therefore in answer to your question, you don't need it because you can set it manually with menu. But it is a convenience which may save you making mistakes by forgetting to set it manually when you change lenses, the result of which may be vignetting / colour cast in the corners of images.
 
ah, so it's more of an automation type thing, gotcha.

Roger, so lenses like the Voigtlander would need to be dealt with after the fact, with cornerfix?
 
daniel buck said:
ah, so it's more of an automation type thing, gotcha.

Roger, so lenses like the Voigtlander would need to be dealt with after the fact, with cornerfix?
Click to expand...

Not quite, you can set the camera manually to an equivalent leica lens. i.e. one of same or close focal length. Some experimentation will tell you which is optimum for your third party (CV) lens and that should give you images which don't require significant fix in software. Maybe no fix. With no coding and forgetting to set lens manually, then yes you need to fix image for lenses that require special processing to correct for angles.

But the M Coder kit will save you from forgetting to set lens manually in camera menu.
 
Last edited:
daniel buck said:
ah, so it's more of an automation type thing, gotcha.

Roger, so lenses like the Voigtlander would need to be dealt with after the fact, with cornerfix?
Click to expand...

If the lens mount is suitable you can code it yourself with either a Dremel supposing there are no screw heads in the coding area, or bars of black paint if there is a groove in the mount as done with the newer CV lenses. If you want to code a screw mount lens you can buy an LTM adapter with code recesses already machined in reday for you to fill with black paint.

Coding only helps with wider lenses than 35mm (adjusting vignetting mainly) but benefits all your Exif data on any lens. You can make your own coding kit

http://bophoto.typepad.com/bophoto/2009/01/m8-coder-simple-manual-handcoding-of-m-lenses.html

but be aware a black Sharpie rarely works with the M9 like it does with the M8. The M9 needs denser black paint, and this rubs off even quicker than a Sharpie, so machined grooves of some sort are the only realistic answer. Ideally you test your coding with black paint, and use the marks as guides for permanent coding with a Dremel (you only need the black marks, the white ones are irrelevent). Many Leica lenses can be sent to Solms for conversion to a coded mount, but the results are the same.

Steve
 
The M8 has no manual lens menu. That is only the M9. The corrections are mostly to correct, As Ben says, system-induced problems. Due to the short register distance of a rangefinder there will be some (extra) vignetting on wideangle lenses, and there will be cyan drift towards the corners due to the IR filtering. The camera automatically corrects for such phenomena before the RAW file is written, as long as it knows which lens is mounted. therefore all Leica lenses since 2006 are coded and the factory will code virtually all older lenses. There are third-party options as well. The camera needs coding to write the focal length to EXIF.
 
tlitody said:
Not quite, you can set the camera manually to an equivalent leica lens. i.e. one of same or close focal length.
Click to expand...

That held true for the M8, but I haven't found that to work very well with the M9. For example on my M8 I used 21/2.8-ASPH code for the Voitlander Skopar, the 28 Summicron code for the Voitlander Ultron f/1.9, and the WATE 16mm code for the Voitlander 15. None of those works well on the M9, suffering from pronounced red-edge. The only code I found that works decently with those 3 lenses is the code for the pre-ASPH 21 Elmarit and only at ISO 160. As ISO increases, so does red-edge, progressively. So a different Cornerfix profile would be needed for each ISO value for each lens. Sandy (Cornerfix inventor) suggests shooting the lenses uncoded, which then requires only one profile for each lens. Since I no longer own an M8 I just painted the code recesses white on those lenses, so I can leave lens detection "ON" for the others.
 
You must log in or register to reply here.
Back
Top Bottom