Help me make sense of the lens codes!

[johnastovall]

Ok, I'm getting an M8. I had hoped to use some older lenses (screwmounts) with adapters on it as well as Zeiss and others. Now it looks like this may not be the case.

My questions:

Should I just stick to the lenses on Leica's list which they will code and forget other kinds of lenses with M mounts?

What about the Zeiss ZM 21mm, I was ready to buy last night? Will it be usable or have a code in the future or just plan on the 21 Elmarit?

 

[jlw]

How about waiting until you get the camera, then try some of your other lenses on it and see how they work without the coding?

My experience with the R-D 1 has been that most of the lenses I already owned, including some really old screwmounts, yielded good results. The only ones that require vignetting compensation are ultrawides, and it's easy to apply that compensation to the raw files on a batch basis.

Nobody will know anything until the M8 actually appears and has been tested, but I suspect that the coding is more of a convenience than a necessity.

 

[kbg32]

The coding as far as I know and what I have read, is for exif data. It won't affect the functionality of the camera for taking pictures.

 

[Mark Norton]

Seems to me they're going to significant lengths if it's only a matter of convenience. We know the camera will include the lens data in the EXIF file header, will display the focal length on the display (in case you're too lazy to look at the lens mount), and will adjust the reflector of Metz flash units (or badged Leica ones).

Beyond that, we don't know much, but it's safe to assume there will be some sort of vignetting correction in the camera but that can only go so far because the camera will not know the working aperture of the lens.

Still, Leica obviously think it's worth the expense and effort of doing it.

I've had my lenses done (sounds like having a cat "done") but more cautious people will play wait and see.

 

[johnastovall]

The coding as far as I know and what I have read, is for exif data. It won't affect the functionality of the camera for taking pictures.

Leica says it goes beyond the EXIF data.

The lens coding is called ‘6-bit coding‘ because six fields in the bayonet ring are marked in
black or white to represent a number from 1 to 64 in binary code. The planned digital M
camera reads this information optically and can identify the lens on the basis of this code.
Apart from the improvement in image quality, this information is also written into the EXIF
image file.

“On account of their legendary quality, nearly all Leica M lenses are ideal for digital use.
However, the new 6-bit coding also uses the performance reserves in the image processing of
the camera to give our customers the excellent image result they expect from Leica,“ says
Rainer Bültert, product manager for the M system at Leica Camera AG.

http://www.leica-camera.us/assets/file/download.php?filename=file_283.pdf

 

[Chris Lynch]

to be completly honest, i'm having trouble understanding what could be done with manual-focus lenses to improve image quality, just by coding.... I'm thinking -possibly- (and this is reaching) that with wides, it does some in-camera vignetting fix? maybe?

but other than that, what could the coding provide?

 

[Bob Ross]

to be completly honest, i'm having trouble understanding what could be done with manual-focus lenses to improve image quality, just by coding.... I'm thinking -possibly- (and this is reaching) that with wides, it does some in-camera vignetting fix? maybe?

but other than that, what could the coding provide?

The first correction will probably be sensor fall off due to the short back focus of M mount lenses. The sensor will probably have off set microlenses, but they may provide offset for a narrow range of focal lengths. After that, as you mentioned, vignetting with wide angles. Now, if they go exotic and use something like DxO to correct distortion, the engineers could have fun, because they know about distortions that we don't even notice. That type of software can also sharpen acording to the resolution profile of a lens design. Could they change those MTF curves to straight lines? Will they cook the Leica look out of the lens fingerprints? Will they create a new Leica look?
It is going to be fun to find out what those dang dots do😀
Bob

 

[Chris Lynch]

can they even DO some of that stuff? hahaha that'd be wild

 

[blakley]

So R3MChris brings up a point which has been bothering me, too....

to be completly honest, i'm having trouble understanding what could be done with manual-focus lenses to improve image quality, just by coding.

Since the coding doesn't help the body know what aperture has been selected on the lens, how does the body figure out what to do....... ?

 

[Bob Ross]

can they even DO some of that stuff? hahaha that'd be wild

Yes, I think it can be done, however a program like DxO is processor intensive and the M8 body might not have the space for an exotic processor. Concepts like this have come up for in-camera lens corrections for P&S digicams.

 

[Bob Ross]

So R3MChris brings up a point which has been bothering me, too....

to be completly honest, i'm having trouble understanding what could be done with manual-focus lenses to improve image quality, just by coding.

Since the coding doesn't help the body know what aperture has been selected on the lens, how does the body figure out what to do....... ?

Sensor fall off is not aperture affected. The angle of light hitting the corners of the frame depands on the focal length, back focus (registration) and lens design (exit pupil). The dots will tell the camera which lens to look up in a table and what to do to the image for sensor fall off.
I keep forgetting that the dots will also tell the TTL flash units how to zoom their flash thingy, too.
Bob

 

[jaapv]

But we can be confident that the quality of the photographs will be fine with uncoded lenses as well, so it is not worth agonising about.

 

[SoBeahKid]

In theory, it should be possible to figure out the aperture by comparing the reading of the main TTL meter with the reading of a small secondary meter that would be directly exposed to the light. It would be a bit clumsy and inelegant but it should work.

 

[jaapv]

If you don't use a filter.....

 

[Mark Norton]

...and both sensors are looking at the same thing...

 

[jaapv]

But on the other hand, the M8 might well have an extra external sensor for colour balance like the Digilux2 anyway. We'll just have to wait and see.....

 

[jdos2]

I have a lens I use on my 5D that's a manual focus- an old 28mm f/3.5 that fits the M42 mount.
If I just throw it on the camera, though, the camera over-exposes. I have to compensate between a stop and two for the pictures, and the compensation is on a curve where I have to compensate less as I stop down the lens.
I'm guessing that this is one of the effects that the Digital Leica will help stop.

 

[SoBeahKid]

That's a good point indeed.

 

[Mark Norton]

I have a lens I use on my 5D that's a manual focus- an old 28mm f/3.5 that fits the M42 mount.
If I just throw it on the camera, though, the camera over-exposes. I have to compensate between a stop and two for the pictures, and the compensation is on a curve where I have to compensate less as I stop down the lens.
I'm guessing that this is one of the effects that the Digital Leica will help stop.

It's possible the aperture cam on your old lens is out of alignment so that when you select f4, it's not actually that when the lens stops down.

It's tough to see how the M8 can correct aberrations which vary by aperture if the camera cannot find out what aperture is in use. I think we'll all be a bit underwhelmed by it though if all it does is a touch of vignetting correction.

 

[jdos2]

There's no connection between the 5D and lens, so the camera doesn't know aperture- just EV as read off the sensors in the camera. That's the trouble- the projection of the lens and camera interact in such a way that the camera over exposes at all apertures, and worse when nearly wide open.

The M8 could figure out aperture as on the G2- if it has an external light meter. We'll see, indeed!