M8 Red Vignetting Over-Correction

[rfnoob]

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Hi all, I'm relatively new to this forum so please point me in the right direction if this has been discussed before.

 

I recently purchased a used M8 and I have 2 lenses which I use with the M8, a 35m Cron ASPH with a B+W UV/IR Cut Filter and a 50mm Summulux v2 with the Leica E43 UV/IR Cut Filter.

 

After a couple of shots, I notice that I like the colour from the lux was more natural and after playing around with the settings and a number of test shots, I noticed that the M8 was over-correcting (sometimes) the red-vignetting from the use of the UV/IR on the 35 Cron.

 

I get a slight red tint in the corners when the Lens Detection is set to On UV/IR.

But when I turn it off, I just get a hint of vignetting across all colours which is similar to my M9 when I'm shooting a 50 Cron at f/2.

 

Anyone else encountered this? Nothing to correct, just turning it off gets me better pictures. But it's a little irritating not to have the lens in the meta-data.

 

Thanks.

[Jark89]

Hi rfnoob, I think your experience parallel's mine. In fact I also started a topic regarding this: http://www.l-camera-forum.com/leica-forum/leica-m8-forum/142932-m8-2-005-coded-35-cron.html

 

Anyway, my 35mm is a version 4 summicron. With a B+W UV/IR on, coded, and Lens Detection "on", I get reddish corners. But only noticeable in certain conditions, ie. shooting white clouds, etc. If I turned off Lens Detection, the corners just had "regular" darkish vignetting.

 

I never really got an answer myself as to why this happens. So now I just shoot without the coding on the lens.

[rfnoob]

Well, it's not really worth a trip to Solms to get it fixed since the pics turn out fine when I turn off lens detection. Also, it onky happens under certain conditions and I think it would be too hard for Leica to reproduce the problem.

 

The onky way I've been able to consistently reproduce it is with an expodisc but I think that actually causes the light to enter the lens fairly perpendicular to the axis and therefore there would be no red vignetting which then will almost certainly result in over correction.

 

Looks like we're the only people to have encountered this problem.

[lct]

... If I turned off Lens Detection, the corners just had "regular" darkish vignetting...

Would you mind showing a pic at f/2 with Lens Detection off? I would like to compare the M8's real vignetting to my Epson bodies' with 35/2 IV.

[UliWer]

...

 

Looks like we're the only people to have encountered this problem.

 

The problem with the "red edges" on wide angle lenses has always been there with the M8 - but it went almost unnoticed until the M9 came. Notwithstanding many opinions which state that the issue is limited to the M9, I know it as well from the M8. It shows slightly different patterns, but I'd not call one of the two cameras better or worse in this respect - which is astonishing as one should think that the M8 crop cuts off a lot from the corners.

 

From my experience I'd say that it is very rare to see the red in the edges with a 35mm-lens, much more so with e.g. the 3.8/18mm. I can also confirm, that with an Expo-Disc you can provoke the red to become extremely obvious, which - fortunately - does not represent what we see on normal photos.

 

In many threads about this issue (with the M9) one can find different sorts of remedy for it: CornerFix or the de-vignetting function in Capture One work pretty good - though it certainly is a nuisance.

[rfnoob]

I've read about red edges on the M9 but not so much on the M8.

 

My take is that it's a sensor problem on the M9 as I have both and have not really seen the problem on the M9 although I've not shot anything wider than a 35mm (Cron and Lux).

 

As to why it occurs on the M8, my understanding is that when one uses an IR cut filter, at wide angles, it also cuts out red which means that there should be some amount of red vignetting, i.e., the picture at the edges appears more blue/green. The software then corrects for this by adding red to the edges.

 

One hypothesis could be that because I'm using a B+W IR cut filter, it's not cutting out as much red at wider angles but the firmware is correcting assuming it's a Leica filter which does cut out more red at the edges. This results in too much red being added to the edges.

[UliWer]

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I've read about red edges on the M9 but not so much on the M8.

 

My take is that it's a sensor problem on the M9 as I have both and have not really seen the problem on the M9 although I've not shot anything wider than a 35mm (Cron and Lux).

 

As to why it occurs on the M8, my understanding is that when one uses an IR cut filter, at wide angles, it also cuts out red which means that there should be some amount of red vignetting, i.e., the picture at the edges appears more blue/green. The software then corrects for this by adding red to the edges.

 

One hypothesis could be that because I'm using a B+W IR cut filter, it's not cutting out as much red at wider angles but the firmware is correcting assuming it's a Leica filter which does cut out more red at the edges. This results in too much red being added to the edges.

 

It's true that the lens correction works different with the M8 and M9, whicvh makes the whole problem difficult.

 

Though it's certainly no fault of different filters. I only had the original Leica filters for the 3.8/18 on the M8 and almost constantly saw the red edges. Just some examples after I got aware of the issue:

 

http://www.l-camera-forum.com/leica-forum/forum-zur-leica-m8/98843-problem-mit-dem-super-elmar-18mm.html#post1040024

 

With 35mm I can remember only one example (snow and underexposure).

[efix]

I've read about red edges on the M9 but not so much on the M8.

 

My take is that it's a sensor problem on the M9 as I have both and have not really seen the problem on the M9 although I've not shot anything wider than a 35mm (Cron and Lux).

 

As to why it occurs on the M8, my understanding is that when one uses an IR cut filter, at wide angles, it also cuts out red which means that there should be some amount of red vignetting, i.e., the picture at the edges appears more blue/green. The software then corrects for this by adding red to the edges.

 

One hypothesis could be that because I'm using a B+W IR cut filter, it's not cutting out as much red at wider angles but the firmware is correcting assuming it's a Leica filter which does cut out more red at the edges. This results in too much red being added to the edges.

 

Interesting ... you haven't conducted any tests with a Leica filter, have you?

I recently had the same problem with my 15/4.5 Heliar with B+W UV/IR filter. In one shot (out of some dozens!) I got the whole left edge tinted in red, plus the bottom left and top right corner. It does indeed look like the cyan drift correction was overdone. But what strikes me is that it happened in only one frame. Might it be because the sun was hitting the sensor at an angle from top right? Light reflecions or something? Anyway, it doesn't happen often, so it doesn't really bother me. Still, would be interesting to know what exactly causes it.

 

EDIT: Here's another thought: It might also have to do with white balance. I noticed that depending on the colour temperature, the cyan drift in the corners is more or less visible even with lens detection + UV/IR set on. The picture above was taken in the mountains in mid-day sunlight. I'd also expect there to have been VERY strong UV and IR reflections from the snow and strong sunlight.

[rfnoob]

No I have not and am not really up to buying a Leica filter to try to replicate the problem. I will try to borrow one and post the results if I'm able to get my hands on one.

 

Yes, I did notice that white balance and exposure do play a part in whether this happens.

[ho_co]

With the exception of the Leica filter for the WATE, all the different brands of UV/IR-Cut filter are the same optically. It has nothing to do with brand of filter.

 

BTW, welcome to the forum!

[rfnoob]

Hi Howard,

 

Thanks, I'm pleasantly surprised at how many helpful people there are here!

 

On the 2 filters, there seems to be some difference because the colour rendering is slightly different when I hold the E43 Leica in front of my 35 Cron compared to using the B+W. The B+W appears to have warmer colours. Again, only way to really see a difference is to get an E39 Leica IR Cut to try out.

 

 

 

Thanks.

 

The noob who's only used digital RFs.

[ho_co]

I've got several Leica and several B+W filters. The latest B+W I got has a completely different surface reflectance, but seems to do the same job on camera.

 

What I said about the filters all being the same is based on hearsay, going back to the time we discovered the M8 needed IR filtration.

 

Leica did say that all their UV/IR-Cut filters were the same except for the one made for their filter adapter for the Tri-Elmar 16-18-21, had fewer layers of the semi-reflective coating.

 

To my knowledge, that's the only UV/IR-Cut filter different from the others; but you've actually experimented with them and I haven't.

[jamesk8752]

I've got several Leica and several B+W filters. The latest B+W I got has a completely different surface reflectance, but seems to do the same job on camera.

 

 

My filter supplier tells me that B+W is now providing their 486 UV/IR cut filter in MRC multicoated form, so if you have a recently manufactured copy you may have the MRC version, which will show much-reduced surface reflection vs. the older single-coated version. It would be interesting to see a comparison of the old vs. new filter in a flare situation.

 

I wish I could afford to replace all of my older Leica and B+W UV/IR cut filters with the new version, but the cost would buy me another lens...

 

Regards, Jim

[rfnoob]

Like the both of you, I have noticed the newer coatings but I have not seen any difference in performance between the 2 although one of them is on a 35 Cron and the other on a 50 Cron.

 

But I put up with the occasional flare/reflection by putting filters on all my lenses ever since the lens hood came off my brand spanking new 35 Cron ASPH and put a light scratch across the lens!