Red filter for monochrom?

[jaapv]

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On 6/18/2021 at 6:14 PM, hdmesa said:

With my 50 Summilux BC and an orange filter, I have to use live view when shooting wide open. However, using a light red filter on my CV 50 APO shows no change, and rangefinder focusing is fine wide open at f/2. Sounds like all non-APO lenses can be affected to varying degrees, at least at wide apertures.

Of course. As I said a long-known phenomenon and impossible to avoid. I find that on most lenses  orange will be OK, as it will be used in landscape photography where we tend to stop down. For the same reason just estimating the correction for a red filter will usually work. Normally about 1/2 a stop on the DOF scale will do the trick.

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[IkarusJohn]

5 hours ago, bilbrown said:

 

 

Orange acts the same as RED with the M10M and M246. I found this an issue the other night with my M10M, the focus shift was so bad I literally thought my eyes (new glasses) were off. The next day I shot the same scene without a filter at the same time and it was perfectly in focus.

I may want to mention, that live view didn't actually help much. This of course could be "user error".. but it makes me want to check a few more times and test. 

This was this the normal Leica orange filter, btw.

What lens?

[hdmesa]

On 6/10/2021 at 11:39 AM, IkarusJohn said:

Depends which version of the Summicron you have.  The first version was highly praised, particularly on film M cameras and the M8.  It didn’t really work that well for me (probably my copy, so I sold it), and it performed poorly on the SL.  I suspect it was one of those lenses found wanting with higher resolution sensors, with their very unforgiving depth of focus.  Leica then released the second versions of the ASPH 35 and 28 Summicrons, which seem to have fixed the problem.

As you say, the shift in the depth of focus will be lens specific (not sure it is “focus shift” in the way people use that expression - unlike the 35 Summilux ASPH, pre-FLE, it’s not a case of focus shifting with changes in aperture). I think it’s largely a theoretical problem, limited to lenses poorly apochromatically corrected on the original Monochrom.  

If you have a later version of the Monochrom it won’t be a problem using red filters if you use live view . 

Just to follow up with this:

With the M10M, the latest 28 Summicron still has so much focus shift with a red filter, it’s unusable with the optical viewfinder unless shooting stopped down at infinity (even then, I would verify infinity with the EVF/LCD). The latest 50 Summicron also has focus shift with a red filter, but it’s not as bad as the 28.

In contrast (pun), the 28 Lux doesn’t seem to have any focus shift with a red filter, so I guess being one of Leica’s most recent wides, it may be an “off-label APO” like the 50 Lux, only newer and better corrected.

[mmradman]

7 hours ago, hdmesa said:

Just to follow up with this:

With the M10M, the latest 28 Summicron still has so much focus shift with a red filter, it’s unusable with the optical viewfinder unless shooting stopped down at infinity (even then, I would verify infinity with the EVF/LCD). The latest 50 Summicron also has focus shift with a red filter, but it’s not as bad as the 28.

In contrast (pun), the 28 Lux doesn’t seem to have any focus shift with a red filter, so I guess being one of Leica’s most recent wides, it may be an “off-label APO” like the 50 Lux, only newer and better corrected.

Lux M 28mm may appear to be corrected when shooting with red filter but I wouldn't call it it APO, either off or on label, it displays colour fringe at maximum aperture when shooting into the light, which is to be expected.  In my practice with M246 and 28mm f1.4 orange is de-facto my standard contrast filter [modern Heliopan MC].  I tried red but no extra darkening observed, could be brand of the filter as I only have old 1980s vintage Hoya R25 filter.  

[hdmesa]

4 hours ago, mmradman said:

Lux M 28mm may appear to be corrected when shooting with red filter but I wouldn't call it it APO, either off or on label, it displays colour fringe at maximum aperture when shooting into the light, which is to be expected.  In my practice with M246 and 28mm f1.4 orange is de-facto my standard contrast filter [modern Heliopan MC].  I tried red but no extra darkening observed, could be brand of the filter as I only have old 1980s vintage Hoya R25 filter.  

True, the fringing when shooting into the sun is pretty bad with the 28 Lux. Yellow to orange seems to be a bigger jump than orange to light red, at least with B+W. I never use the dark red since it’s a bit too much light loss for my use. I wouldn’t be surprised if there is some variance in strength between brands.

[pippy]

As BrianS mentions in post #6 the 50mm f1.5 Summarit has an IR focus mark. On these lenses it is fractionally outside the f2 D-o-F mark.

I've just carried out a small - non-scientific - experiment with a few lenses in (roughly) the 'standard' f/l and, FWIW, here's the outcome;

 With my M Monochrom fitted, first, with the Summarit I put on a Leitz Red (x4) filter and, choosing a suitably distant subject, shot three frames with infinity set to the IR mark Unsurprisingly it worked at the three apertures chosen for the test; wide-open (here f1.5), f4 and f8.

I then did much the same proceedure(*) with a Summicron v4; a 'Serenar'-era Canon f1.8 LTM and, out of interest, a 40mm f1.4 Voigtlander Nokton. None of these lenses has an IR mark so I simply placed infinity to a similar position relative to the f2 D-o-F mark each time.

All the 50's worked pretty much perfectly when set to the 'virtual mark'. Certainly by the time the DNG images were processed-out and with a small amount of sharpening applied no-one would question the sharpness of the images.

The 40mm Nokton, however, was still slightly soft which leads me to believe that a marginally different spot on the barrel would result in sharper images. More work to do...

This was all just a hastily-rigged test. I'll try to do some more representative snaps when the weather improves!

Philip.

* Max. apertures varied, of course, with each lens but the results were pretty much identical in each case regardless.

[mmradman]

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3 hours ago, pippy said:

As BrianS mentions in post #6 the 50mm f1.5 Summarit has an IR focus mark. On these lenses it is fractionally outside the f2 D-o-F mark.

I've just carried out a small - non-scientific - experiment with a few lenses in (roughly) the 'standard' f/l and, FWIW, here's the outcome;

 With my M Monochrom fitted, first, with the Summarit I put on a Leitz Red (x4) filter and, choosing a suitably distant subject, shot three frames with infinity set to the IR mark Unsurprisingly it worked at the three apertures chosen for the test; wide-open (here f1.5), f4 and f8.

I then did much the same proceedure(*) with a Summicron v4; a 'Serenar'-era Canon f1.8 LTM and, out of interest, a 40mm f1.4 Voigtlander Nokton. None of these lenses has an IR mark so I simply placed infinity to a similar position relative to the f2 D-o-F mark each time.

All the 50's worked pretty much perfectly when set to the 'virtual mark'. Certainly by the time the DNG images were processed-out and with a small amount of sharpening applied no-one would question the sharpness of the images.

The 40mm Nokton, however, was still slightly soft which leads me to believe that a marginally different spot on the barrel would result in sharper images. More work to do...

This was all just a hastily-rigged test. I'll try to do some more representative snaps when the weather improves!

Philip.

* Max. apertures varied, of course, with each lens but the results were pretty much identical in each case regardless.

Maybe in addition to 6-bit coding for old lenses new M lenses need to be retrofitted with IR focus scale marking.