[New test photos released] Leica Summicron 35/2 Eight Element copy made in China

[yossi]

Thank you for understanding my intention!

While it's easy to say 'just use it and enjoy it' when one's own copy lives up to one's expectations, it would be the first time in ~30+ years I've owned a lens that becomes soft at f/4-5.6 in only the center of the frame, which effectively makes it unusable (without resorting to live view) other than near wide open or stopped down to f/11.

Interestingly though, if I only had a mirrorless camera and received this copy, I'd be wondering why it was only sharp in the center until f/11...

Regarding field curvature, here is what is published by LLL - a scan of the information included with the lens.

The first image is as published, which represents half of the image circle diameter.

The second image I've taken the graph and flipped it sideways, copied it, flipped the copied layer and then put them side by side to illustrate what field curvature should be like across the full image circle.

You can see that the wavy field curvature means that with ideal focus at the center, the plane of focus would move to front focus in the mid zone area and then curves at the edges to fairly strong back focus. By placing the plane of focus to intersect the subject plane a bit outside of dead center, with sufficient depth of field, there will be good across-frame sharpness. I believe that is how my copy is RF calibrated. But my copy's wavy field curvature undulates to such an extent that depth of field doesn't fully cover it until f/11. My copy changes from fairly flat field curvature wide open to very wavy by f/4.

The third photo is what I posted before - the Find Edges version of a test photo to show the shape of field curvature at f/4 from my copy. It sure looks stronger than the field curvature published by LLL.

Re-examining those test shots that I took, now I am convinced that the plane of focus of my copy does tally with the LLL-published field curvature. The wavy curvature is certainly there but not that severe as yours. As I shoot mostly wide-open or f8 and smaller, it should be fine.

 

[D&A]

Re-examining those test shots that I took, now I am convinced that the plane of focus of my copy does tally with the LLL-published field curvature. The wavy curvature is certainly there but not that severe as yours. As I shoot mostly wide-open or f8 and smaller, it should be fine.

Based on all we discussed and shown so far, I have two thoughts and comments:

1. My sample and some of those shown early in the process of receiving their replica lenses...appears to show that at the very edges/corners, that the field curvature bows inwards. Its clearly shown in the two pics I posted recently and I consistently saw in most all my series of test shots. It also appears that there is little focus shift and that the subject focused on in the center of the frame gets progressively sharper upon stopping down and the surrounding depth of field does not move rearward (or forward for that matter) to any appreciable measure. The depth of field just gets larger as expected. Therefore from what I observed (with my sample), is that it can be used at any f-stop, with confidence the subject focused on remains well within the depth of field.

2. Based on the above, it appears the recently released sample of rscheffler. of the replica behaves quite differently. Whether this is by design due to a optical change in the lens, or is an anomaly with that one particular sample, its hard to say at this point, but for a lens that's only really usable at wide open (f2) and then only at f11, does make much sense.

Dave (D&A)

 

[kiemchacsu]

I've not done any test, but only use it for practical shooting.
this one below was shot at F2 at MFD.
Judge the lens' performance following this link with full resolution.



2012_M2LLL35_Arista200_05 by Trung Nguyen, on Flickr

 

[Erik van Straten]

Beautiful shot, Trung!


Erik.

 

[Platinum RF]

Does this mean flint glass (lead) may not available after the first batch (the uneven aperture scale) and they have to use new eco friendly glass?

 

[D&A]

I may be completely mistaken, but a previous posting by another form member a few pages back I believe mentioned their even spacing aperture scale lens "does" have flint glass. Again this would have to be confirmed.

Dave (D&A)

 

[raid]

I also recall that second version lenses have Flint glass in them.

 

[rscheffler]

Does this mean flint glass (lead) may not available after the first batch (the uneven aperture scale) and they have to use new eco friendly glass?

I asked Kevin this exact question a few days ago, and he said he was told by the factory that current production continues to use flint glass and that there have been no optical changes. That is what he was told. Whether he was told the truth, I cannot say.

I sent my examples link to him with explanations and he will forward it to the factory for analysis. I'll update once I hear their response.

 

[james.liam]

Are all flint glass the same? In other words, will one type have different optical effects than another? Can this account for the variability in FC of the image created?

 

[D&A]

I asked Kevin this exact question a few days ago, and he said he was told by the factory that current production continues to use flint glass and that there have been no optical changes. That is what he was told. Whether he was told the truth, I cannot say.

I sent my examples link to him with explanations and he will forward it to the factory for analysis. I'll update once I hear their response.

Thanks, it will be good to hear of the analysis of your lens. The other forum member who also posted a couple pages ago and recently received their lens with the new even spacing of the aperture numbers, was told there "was" changes to the optics of the lens to reduce contrast and some sharpness in order to more closely emulate the original Leica 8 element cron. I'm sure all this will get sorted out.

Dave (D&A)

 

[rscheffler]

Yes, hopefully...

Are all flint glass the same? In other words, will one type have different optical effects than another? Can this account for the variability in FC of the image created?

This also crossed my mind. I'd guess there is/was a range of flint glass 'flavors' available.

We may never know for sure in respect to the various production stages of the replica project.

I'm waiting for performance feedback from another recent replica recipient. It would be great if other recent recipients could also chime in. It could be as simple as one test image:

Shoot something/anything at f/4 at a moderate distance using the rangefinder for focus and keeping the subject in the center of the image.

Is the subject sharply focused?

 

[Erik van Straten]

In the past, mainly flint glass and crown glass were used. Flint glass has a high color separation and contains a lot of lead. Crown glass has a low color separation. Combining both types can correct chromatic aberration. However, lead is bad for the environment. That is why today flint glass is being replaced by aspherically cut glass. LLL will therefore try to replace the design flint glass with something else. Flint glass is still used in the first copies of the LLL8. Perhaps other types of glass were used in later production that cause the focal plane problem.


Erik.

 

[Mech-Dragon]

I was told by Wen who sold me the lens that the optics were tweaked slightly, to bring in more shadow detail but at the trade off of slightly less sharpness. I repeated it here as it was some interesting information on the development of this lens. Not sure if who was the primary source of that information.

I'm curious to see what kind of field curvature I get with some test shots. I'm no expert by any means, but I do know some Photoshop!

My lens is the newer, even aperture scale with half stop clicks. My copy does have flint glass, and an amber coating. Some of my practical images I've taken are a few pages back.

 

[jonmanjiro]

Are all flint glass the same? In other words, will one type have different optical effects than another? Can this account for the variability in FC of the image created?

Flint glass is a generic term for optical glass with a refractive index that falls within a certain range, traditionally achieved by adding lead oxide, and more recently by adding titanium dioxide and zirconium dioxide. See https://en.wikipedia.org/wiki/Flint_glass

The tweak Mech-Dragon mentions above may have been made to accommodate a new type of flint glass with a slightly different refractive index.

You pick the refractive index that meets the requirements of the optical formula. If you need to use a flint glass with a slightly different refractive index for whatever reason (supply issues etc.), you're essentially changing the optical formula, so the optical formula will need tweaking. If the optical engineers do a good job you won't notice any difference in the images produced. For example, the RF Nikkor-H 5cm f2 lens went through about 20 optical revisions through the course of its production.

 

[james.liam]

In the past, mainly flint glass and crown glass were used. Flint glass has a high color separation and contains a lot of lead. Crown glass has a low color separation. Combining both types can correct chromatic aberration. However, lead is bad for the environment. That is why today flint glass is being replaced by aspherically cut glass. LLL will therefore try to replace the design flint glass with something else. Flint glass is still used in the first copies of the LLL8. Perhaps other types of glass were used in later production that cause the focal plane problem.

Erik.

It's a real geek's exercise in re-creating this lens, like efforts to clone a wooly Mammoth. So long as the Mammoth doesn't bark like a schnauzer.

Flint glass is a generic term for optical glass with a refractive index that falls within a certain range, traditionally achieved by adding lead oxide, and more recently by adding titanium dioxide and zirconium dioxide. See https://en.wikipedia.org/wiki/Flint_glass

The tweak Mech-Dragon mentions above may have been made to accommodate a new type of flint glass with a slightly different refractive index.

You pick the refractive index that meets the requirements of the optical formula. If you need to use a flint glass with a slightly different refractive index for whatever reason (supply issues etc.), you're essentially changing the optical formula, so the optical formula will need tweaking. If the optical engineers do a good job you won't notice any difference in the images produced. For example, the RF Nikkor-H 5cm f2 lens went through about 20 optical revisions through the course of its production.

...or more recently, the 28 Summaron redux, I guess. Same to be expected from the 35 Summaron f/2.8 and 50 Noctilux f/1.0 rumored to be due out next year. But those are or will be 6-bit coded, with manufacturer's warranty and adjusted for digital.

 

[rscheffler]

I was told by Wen who sold me the lens that the optics were tweaked slightly, to bring in more shadow detail but at the trade off of slightly less sharpness. I repeated it here as it was some interesting information on the development of this lens. Not sure if who was the primary source of that information.

I'm curious to see what kind of field curvature I get with some test shots. I'm no expert by any means, but I do know some Photoshop!

My lens is the newer, even aperture scale with half stop clicks. My copy does have flint glass, and an amber coating. Some of my practical images I've taken are a few pages back.

Thanks for the added info. I noticed in my aperture sequences that contrast jumps considerably between wide open and f/2.8. Shadow values wide open have a bit of milkiness in comparison.

I'm curious how they define slightly less sharpness. Would it be lower absolute resolution, such as in the center of the image? Or would it be less sharpness across the frame (like gradual loss of sharpness towards the edges)? Based on my copy, at f/2 it has relatively low critical sharpness with SA mixed in, but its level of sharpness is pretty even across the image. I've found it quite pleasing in use. It's in the f/3.5 to about f/8 range where it goes wonky in the center.

If you're doing test shots, check if you get good sharpness in the center of the image at f/4 and f/5.6. If you're shooting film, you'll probably have to check the negatives with an 8x loupe, or at least print them as 8x enlargements. I found with my digital images printed to that size, I could still see the differences, but it wasn't huge. For sure if printed as 4x6 or 5x7 it would be very difficult to notice. If you are seeing odd loss of central sharpness, try a shot or two of a given scene intentionally front focused. For example, with my copy, subjects at near infinity required setting the focusing ring to about 7m at f/5.6 for best central sharpness. But then things at the sides of the image went out of focus. If you're getting good results at f/5.6 across the image, then the lens's inherent field curvature is likely masked by depth of field, as it should be.

 

[rscheffler]

Here's the difference I'm seeing between f/2 and f/2.8 in respect to contrast. I guess some of the drop in contrast in this shot is a combo of SA with a touch of veiling from the bright sky in the background.

 

[D&A]

If that top shot is f2 and the bottom shot is f2.8, I'm seeing just the opposite, What I am observing is the top shots has less contrast and somewhat less sharpness (after all its f2). The 2nd shot shows more contrast and sharpness and greater depth of field...exactly what one would expect when stopping down an f2 lens to f2.8. Now if you said the top shot was f2.8, I'd begin to worry. On a side note, the upper right and left hand corners show those very sharp tree branches (where branches everywhere else within the same approx plane are soft.)...the same phenomenon as seen in most all of the replica lenses.

Dave (D&A)

 

[steveyork]

This is a nice lens for B&W film. Glad all are enjoying their copies, or too to be enjoying. So well made. Worth the wait.

In Search of Trolls by Steve, on Flickr

yellow filter, Foma 100 in HC-110 (1:31)

 

[raid]

What are in the end the definite conclusions on the replica lens design changes (or not) and the associated wave shaped focus profile? Is it an issue only with the later made lenses that have been made with half click apertures or is it a universal issue? Is it a "problem" issue? This thread was loaded with praises for the lens. I feel that such unresolved issues may negatively impact the future of replica lenses at RFF.