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APO Summicron 50/2 ASPH: Central veiling flare / fogging


pajamies

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Upon request, a few additional comparisons have been made, this time with slightly less demanding lighting conditions than showed further up in this thread.

 

In the following 3 posts: M240, no processing, no filter, aperture f2/5.6/16, shutter spd 2000/250/30, lens shade not used (for the purpose of the illustration), on tripod.

 

Sun from a (very) clear sky into the lens. For this test, I was looking for loss of contrast against a dark background.

 

First triple out is APO Summicron 50. Slight loss of contrast in the central/upper image found at f5.6/16.

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Edited by helged
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Second triple is Summilux 50, latest version. As with APO Summicron 50, slight loss of contrast in the central/upper part of the image at f5.6/16.

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Edited by helged
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And then 50 Summicron, latest version. This lens shows some loss of central contrast at f2, and the familiar Summicron-beam creeps in at f5.6/16.

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Edited by helged
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And finally, to mimic Jim's test in post #86-88, the following images are taken against intense highlights, but with frontal lens elements in shade. Central contrast holds up quite well. I don't post Summilux and Summicon for this case, but Summilux behaves similarly to APO Summicron, whereas Summicon shows quite some loss of central contrast.

 

Likely I will use the APO Summicron 50 extensively during the following weeks, so time will show whether the lens continues to impress. I think so.

 

APO Summicron 50, M240, no processing, no filter, aperture f2/5.6/16, shutter spd 3000/350/45, lens shade not used (for the purpose of the illustration), on tripod.

 

Now - time to enjoy the (northern hemisphere) summer!

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Edited by helged
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A couple of points (I'm just becoming aware of this 50 AA Summicron question):

 

1) In helged's series about post #119-121, one key characteristic of the flare from all three lenses shown in that series is that there is a dark band "protected" from the flare, across the top of the images, in all cases.

 

This means that the flare in these examples is caused by the sun's image falling on the floor of the camera chamber, and reflecting onto the sensor from the camera itself (rather than a reflection within the lens glass or barrel itself). The dark band is where the rim of the shutter window shades the edge of the image area from the shiny floor of the camera chamber. (I know, I know, in Latin languages that is redundant - a "chamber" often is a "camera." ;) )

 

In effect the lenses are all producing "too big" an image circle, and a rectangular lens hood exactly sized to the field of view (thus vignetting the image down to the edges of the shutter opening) would eliminate this.

 

2) As to the gentler veiling spot shown in the many other examples, I have encountered similar "hot spots" with at least two other ASPH lenses - the 75 f/2 and 35 f/1.4. These have - in common with the 50 ASMA - a concave rear element. In effect a convergent mirror lens right in front of a relatively shiny silicon-and-glass flat mirror (the sensor).

 

In the two samples below, the light source itself was far, far outside the image area. In the 75 shot, a soft box directly over the subject; in the family snap, well behind the camera. The flare spots ARE associated with a brighter area of the subject matter, however (light clothing or a white chicken). They are also (as with the 50 AA) associated with small aperture settings.

 

I have never seen this effect happen with lenses that have convex rear surfaces, either earlier designs, or even APO-ASPH lenses that manage to avoid the concave rear-element design (e.g. 90 Summicron AA).

 

It is my considered opinion (to which the 50 AA situation adds another data point) that these concave rear elements - whatever other optical magic they may perform - are inappropriate for use in front of a shiny digital sensor. I believe they are prone to reflecting back to the sensor (somewhat refocused, rather than dispersed, by the concave surface) bright areas of the subject first reflected by the sensor surface itself.

 

The first (and only, for a decade) Leica M lens to use such a concave back surface was designed well before the digital era (35 Summilux Aspherical and ASPH- c.1990-92. I think it behooves Leica and Peter Karbe to examine whether they should still be pursuing this technique in designing lenses in the digital era.

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Thanks Andy (post 149) - I didn't explicitly mention the upper band with strongly controlled/no flaring - I was hoping that someone would chime in on this. You did.

 

It would be interesting to play with a restrictive lens shade to check the flaring response. I have the Heliopan metal hoods on order, but I don't know when they will show up.

 

Other appropriate lens shades out there?

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Check your rangefinder calibration :D

 

Don't think so; this is my second M9 and second copy of the Summilux and my observations are identical plus images from the Summilux 50 have been razor sharp from both copies of the lens and both camera bodies. For some reason though, I've been having far fewer problems with moire than I had with the Cron 50 pre-asph. With similar subjects - typically things like tree branches, bales of hay, fabrics etc. And I have very few moire problems with the S2 (and there is no rangefinder to calibrate there...); again images so sharp you can count every pore of someone's skin. This leaves me a bit perplexed - on the M9 it was only the 50 Cron pre-asp - and no other lens - that was consistently producing moire problems (plus veiling flare).

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...

This means that the flare in these examples is caused by the sun's image falling on the floor of the camera chamber, and reflecting onto the sensor from the camera itself (rather than a reflection within the lens glass or barrel itself). The dark band is where the rim of the shutter window shades the edge of the image area from the shiny floor of the camera chamber. (I know, I know, in Latin languages that is redundant - a "chamber" often is a "camera." ;) )

 

....

 

The image in a camera is recorded upside down...

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And finally, to mimic Jim's test in post #86-88, the following images are taken against intense highlights, but with frontal lens elements in shade. Central contrast holds up quite well. I don't post Summilux and Summicon for this case, but Summilux behaves similarly to APO Summicron, whereas Summicon shows quite some loss of central contrast.

 

Likely I will use the APO Summicron 50 extensively during the following weeks, so time will show whether the lens continues to impress. I think so.

 

APO Summicron 50, M240, no processing, no filter, aperture f2/5.6/16, shutter spd 3000/350/45, lens shade not used (for the purpose of the illustration), on tripod.

 

Now - time to enjoy the (northern hemisphere) summer!

Helged....thanks so much for spending the time to prepare and post these shots. Really helpful. As someone who, at least in part, set this hare running last week with the three images shot at 2/5.6/16 I am really pleased that you are having no problems as it gives me hope that I've just got a dodgy lens that can be fixed! I so want this lens to work well across the aperture range as I can see its magic when wide open. I also want to make it my standard lens for my Monochrom, in place of the Nocti. Anyway, I've sent it back to Solms through my dealer and we'll see what happens.

Was very interested in Adan's images too...I have a similarly problem with my 75 in terms of the central veiling...which similarly frustrates me (I am currently considering trading down to the summarit which apparently doesn't have this problem?).

My 18 months with Leica have been an interesting discovery for me (having been Canon). On the one hand, mostly magical/unbeatable image quality and an absolute joy to use the m9/Monochrom/240. On the other hand, an expectation that the glass would be 'perfect' (and it is pricey!)...which is just not the case under some conditions (maybe an unreasonable expectant on my part!). I remain a true Leica fan (if a little frustrated at times!) but am learning that there is much more to these lenses than meets the eye. My go to lens remains my 35 lux...and it's never let me down yet...so here's hoping!

Best wishes, and thanks again,

Jim

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Thanks Andy (post 149) - I didn't explicitly mention the upper band with strongly controlled/no flaring - I was hoping that someone would chime in on this. You did.

 

It would be interesting to play with a restrictive lens shade to check the flaring response. I have the Heliopan metal hoods on order, but I don't know when they will show up.

 

Other appropriate lens shades out there?

 

B&H has this Leica 39mm Hood. Curious if it would be a tad longer than what comes on the APO 50.

108473.jpg

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Sun from a (very) clear sky into the lens. For this test, I was looking for loss of contrast against a dark background..

 

Helged,

In post #143, can you tell roughtly at what angle the sun shines into the lens?

Thanks.

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B&H has this Leica 39mm Hood. Curious if it would be a tad longer than what comes on the APO 50.

http://static.bhphoto.com/images/images500x500/108473.jpg

 

No - tried it yesterday.

If it could screw into the existing hood as an extension, it'd be great.

That one screwed into the lens is just shorter than the built-in.

Now, two of those Elmar hoods together would be an interesting experiment to try...

 

The built-in hood has threads, and measures out to approx. 44mm, which no one makes a hood in the thread size.

 

But so far, I cannot replicate any flare or loss of contrast on my 50AA, so I'm not planning to worry about it!

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No - tried it yesterday.

If it could screw into the existing hood as an extension, it'd be great.

That one screwed into the lens is just shorter than the built-in.

Now, two of those Elmar hoods together would be an interesting experiment to try...

 

The built-in hood has threads, and measures out to approx. 44mm, which no one makes a hood in the thread size.

 

But so far, I cannot replicate any flare or loss of contrast on my 50AA, so I'm not planning to worry about it!

That is great to know. It is not cheap at $69 but cheaper a lot of Leica hoods. Heavystar on ebay has a metal 39mm hood for about $10 shipped and it looks deeper. But I am not having any of the issues either so far, just thought I would mention som alternate hood options. Like someone said earlier in this thread, I think it was Platypus, I wish I was a better photographer.....:p

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