New Sean Reid Article

[rvaubel]

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I'm sorry that I have to admit that it's quite difficult to follow all these mega long threads.

 

I understand these discussions as a learning process to understand how good the work arounds found by some members really are. For example user camera profiles, usage of profiles from medium format digital backs etc.

 

What's the intended benefit?

a) Finding 'usable' temporary work-arounds until Leica presents their final solution (filter availability)?

Finding your own final solutions because you cannot live with the filter solution?

c) RAW developing for better colours because you don't like M8's colours beside the magenta problem?

 

I'm sure it would be helpful for many readers if one of the key posters could spend a few minutes to sum up in a few sentences 'where you are' and what the key results of all these discussion are at this point.

 

Thanks in advance.

 

Philip

 

Fortunately, all the above.To get to the point

 

1) the problems aren't really all that bad....and its a great camera

 

2) There are so many different solutions to the problems, that no one solution fits every user. We are currently in the process of figuring out the range of solutions available. Most people are figuring that with the many choices that are developing that something will fit into their workflow even though it isn't entirely clear what those individual choices are yet.

 

Is that clear?

 

Rex

[like_no_other]

Fortunately, all the above.To get to the point

 

1) the problems aren't really all that bad....and its a great camera

 

2) There are so many different solutions to the problems, that no one solution fits every user. We are currently in the process of figuring out the range of solutions available. Most people are figuring that with the many choices that are developing that something will fit into their workflow even though it isn't entirely clear what those individual choices are yet.

 

Is that clear?

 

Rex

 

Has your answer someting to do with the 'TEXAS solution deriving model'?

 

My English is not the best but I understand everything.

[sean_reid]

Philip,

 

Sure... In a nutshell, we're trying to understand patterns of cyan drift and vignetting and how they relate to focal length, lens type and aperture. The ultimate goal, in my case, is to figure out which lenses can probably be coded as if they were specific Leica lenses with good results. I'm putting my own results into practice now as I hand code various lenses and/or LTM/M adapters. So far I have coded:

 

CV 28/3.5 with Leitz adapter

Canon 28/2.8 with same Leitz adapter

CV 35/2.5

CV35/1.7 with Leitz adapter

Zeiss 35

Zeiss 28

 

I'm also working on coding adapters for the CV 25 and CV 21. The implications of all this can potentially be useful for any lens that is not already on Leica's "codable" list. Many of those are Leica's own LTM lenses. One we understand the patterns (and I now have enough of a sense of them to have begun coding) we then see how things play out in practice.

 

Cheers,

 

Sean

[waterlenz]

Jean,

 

We have moderators here. E-mail them to get whatever clarifications you need about what is and is not seen as promotion, abuse, etc. Then, once you get this out of your system, see what constructive things you can contribute to the forum.

 

I hope we do not have a repeat of what happened over on FM

Tom

[waterlenz]

Philip,

 

Sure... In a nutshell, we're trying to understand patterns of cyan drift and vignetting and how they relate to focal length, lens type and aperture. The ultimate goal, in my case, is to figure out which lenses can probably be coded as if they were specific Leica lenses with good results. I'm putting my own results into practice now as I hand code various lenses and/or LTM/M adapters. So far I have coded:

 

CV 28/3.5 with Leitz adapter

Canon 28/2.8 with same Leitz adapter

CV 35/2.5

CV35/1.7 with Leitz adapter

Zeiss 35

Zeiss 28

 

I'm also working on coding adapters for the CV 25 and CV 21. The implications of all this can potentially be useful for any lens that is not already on Leica's "codable" list. Many of those are Leica's own LTM lenses. One we understand the patterns (and I now have enough of a sense of them to have begun coding) we then see how things play out in practice.

 

Cheers,

 

Sean

 

 

I seems to me that you would have to have a complete database of the effects of all the coded Leica lenses to find the best match for any given uncodable lens, Leica or otherwise

Tom

[waterlenz]

 

Finally, I would like to see what the influence of the exit pupil (as opposed to the focal length) is in accounting for the differences between these lenses' behaviors. But I don't have that information.

scott

 

I have been wondering the same question. It may be answered by adapting an SLR lens and comparing to Leica and other rangefinder lenses. Plan on doing this myself with the Novoflex adapter and my Nikkor collection. I expect the 35 1.4 asph to blow away the 35 1.4 Nikkor (decades older design) :-}}

Tom

[rvaubel]

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I will bet dollars to donuts that the main parameter that dictates the amount of radial cyan shading is the back focal length of the EXIT PUPIL, not the focal length of the lens. In fact, I will bet it is the only determining variable.

 

Rex

just sticking my neck out in Bezerkeley

[scott kirkpatrick]

I will bet dollars to donuts that the main parameter that dictates the amount of radial cyan shading is the back focal length of the EXIT PUPIL, not the focal length of the lens. In fact, I will bet it is the only determining variable.

 

That's not what I expected, since the angle-sensitive IR filter is out in front, where every lens sees the same angle of view, since they all end up making the image expected of a 28mm lens. (Well, almost, there was a slight sideways jump in the vertical electrical conduit in Sean's first pass at white wall images, with the telephone. The first three lenses, the smaller ones, looked as if they might have a slightly longer actual focal length then the last four, which are more telecentric.)

 

Plotting up the featureless white wall images (many posts back) it looks like both the front and back angles matter. This could mean that some of the red vignetting happens in the photometric filter, the thin layer of blue-green glass glued to the Kodak chip. It also has angle sensitivity, suppressing reds more when the path through it is longer. Adding pictures to the set in which the IR filter is left off will help to separate these effects.

 

scott

[rvaubel]

That's not what I expected, since the angle-sensitive IR filter is out in front, where every lens sees the same angle of view, since they all end up making the image expected of a 28mm lens. (Well, almost, there was a slight sideways jump in the vertical electrical conduit in Sean's first pass at white wall images, with the telephone. The first three lenses, the smaller ones, looked as if they might have a slightly longer actual focal length then the last four, which are more telecentric.)

 

Plotting up the featureless white wall images (many posts back) it looks like both the front and back angles matter. This could mean that some of the red vignetting happens in the photometric filter, the thin layer of blue-green glass glued to the Kodak chip. It also has angle sensitivity, suppressing reds more when the path through it is longer. Adding pictures to the set in which the IR filter is left off will help to separate these effects.

 

scott

 

Hmmmm, maybe your right. So much for my dollars.

 

I think what I was trying to say is that the cyan effect in a lens without a filter is determined by exit pupil FL and not lens FL.

 

With a lens filter the whole thing gets to complex for my poor brain at this time of night.

 

Rex

empericalism rules!

[like_no_other]

Philip,

 

Sure... In a nutshell, we're trying to understand patterns of cyan drift and vignetting and how they relate to focal length, lens type and aperture. The ultimate goal, in my case, is to figure out which lenses can probably be coded as if they were specific Leica lenses with good results. I'm putting my own results into practice now as I hand code various lenses and/or LTM/M adapters. So far I have coded:

 

CV 28/3.5 with Leitz adapter

Canon 28/2.8 with same Leitz adapter

CV 35/2.5

CV35/1.7 with Leitz adapter

Zeiss 35

Zeiss 28

 

I'm also working on coding adapters for the CV 25 and CV 21. The implications of all this can potentially be useful for any lens that is not already on Leica's "codable" list. Many of those are Leica's own LTM lenses. One we understand the patterns (and I now have enough of a sense of them to have begun coding) we then see how things play out in practice.

 

Cheers,

 

Sean

 

 

Sean, thank you very much for the explanation. This is a very valuable work for all users of third party lenses. Keep on your efforts. I wish you lots of success with your analysis.

 

Best regards,

Philip

[scott kirkpatrick]

Hmmmm, maybe your right. So much for my dollars.

 

That's OK, in return I can offer jelly donuts, the food for Hanuka, which will probably start before I get my own M8.

 

I think what I was trying to say is that the cyan effect in a lens without a filter is determined by exit pupil FL and not lens FL.

 

With a lens filter the whole thing gets too complex...

 

Exit pupil information is still a mystery to me. Erwin Puts doesn't tabulate it in the Leica Lens Compendium. Joseph S. Wisniewsky says that he only measures it on an optical bench for technical lenses that he has personally worked with. It's certainly possible that there are 28mm lenses (like the CV Ultron 28/1.7) with exit pupil distances greater than that of symmetric 35mm "pancake" lenses, since the lengths of the 28mm lenses that Sean Reid has measured vary by almost 28mm.

 

In the meantime, I'll bet that if you work with Steven Gandy at Cameraquest to be your retail channel and gatherer of raw materials you could have a nice business producing a kit for permanently encoding any CV lens to enable firmware and the proper viewframe on the M8 as soon as the Leica filters and final firmware is shipping. Leica's $150 for six dots provides a price umbrella. And the table of codings and recommendations for best match is moving along nicely.

 

scott

[sean_reid]

I hope we do not have a repeat of what happened over on FM

Tom

 

No, the FM thing actually came about when myself and others challenged Fred's inconsistencies in his policies on the forum. Myself, my wife (also a photographer) and various other people were all banned for those posts which were then conveniently deleted. Several people on this forum were around on FM when all this happened. Very totalitarian all in all. Anyway that's an old soap opera and I don't want to get back into it. There are already too many threads on camera forums that are more about soap operas than photography.

 

Back to the M8.

 

Sean

[sean_reid]

I seems to me that you would have to have a complete database of the effects of all the coded Leica lenses to find the best match for any given uncodable lens, Leica or otherwise

Tom

 

Ideally, yes, but lacking that, pragmatic experimentation with combinations will be useful. I suggest we work with whatever we have.

 

Cheers,

 

Sean

[sean_reid]

Sean, thank you very much for the explanation. This is a very valuable work for all users of third party lenses. Keep on your efforts. I wish you lots of success with your analysis.

 

Best regards,

Philip

 

My pleasure. This may also be useful for the many Leica lenses (M and LTM mount) that are not "codable" right now. There are a lot of them and the wide angles will all need some kind of cyan drift correction to be useable for color work with filters.

 

Cheers,

 

Sean

[sean_reid]

It's certainly possible that there are 28mm lenses (like the CV Ultron 28/1.7) with exit pupil distances greater than that of symmetric 35mm "pancake" lenses, since the lengths of the 28mm lenses that Sean Reid has measured vary by almost 28mm.

scott

 

28/1.9 actually

 

Best,

 

Sean