New Summarits' MTF graphs

[Nemo]

Leica has published a new brochure with MTF graphs:

http://www.leica-camera.us/assets/file/download.php?filename=file_3234.pdf

They are really good. See, for instance, the Summarit-M 75mm...

This "practical experience" report is interesting too:

Leica Camera AG - Photography - Summarit-M lenses

 

[Marc-A.]

Hi Nemo,
Thanks for the post, though I can't read those MTF graphs; can you (or anybody else) explain or translate them?
The "practical experience" report is interesting indeed. I find the picture too clinical, digital ... or cligital... besides I wonder why the photographer shoots only at f4 - 5.6, even for a close portrait. How about wide aperture (2.5-2.8)? Just wonder.

 

[awilder]

From reading the MTF graphs that optically these lenses will perform equal to the faster siblings at similar apertures. The benefit will be in cost and compactness. I expect if multicoated, the 50/2.5 to be freer of secondary reflection like the ZM Planar, something the Summicron needed improvement given it's 27+ year age. The optical layout is similar to the Planar with fewer plano surfaces. Mechanically, who knows, but I expect it to be quite good.

 

[Lance]

I am sort of in the market for a 35... well window shopping anyway.

The cron is my ideal want, but I find it hard to justify when the Biogon in many peoples eyes is as good and less expensive. Would the Summarit be a good in between lens? Pricewise, size but will the quality be the same and the only downside the aperture? I know you can't answer because the lens is not out yet. Just thinking out loud.

 

[keithwms]

The charts look good especially in terms of how the S and M curves overlap at lower frequencies, so one can expect marvelous bokeh. But on the other hand these lenses are a bit on the slow side; my guess is that many users are willing to give up a bit in terms of ultimate performance if it means they can work two stops faster. Stopped down to 5.6, these new lenses do look better center-to-edge than the comparable older lenses at f/8, judging by the charts at photodo. But will fast shooters care?

Nice to see new lenses of this quality.

 

[venchka]

Someday I must get my lenses out and make some photos of MTFs.

Or maybe not.

Definitely not.

I prefer to make photos of things I can recogize.

 

[Gabriel M.A.]

The 50mm f/2.5 so-called Summarit (my Summarit is f/1.5) has a diagram which is a virtual copy of the Summicron.

I dunno...call me crazy, but I'd rather have a slightly faster Summicron than the so-called Summarit.

The 35mm and 90mm look good. But at those apertures, I'd rather get the CV offerings. I don't understand their strategy here.

 

[Didier]

The 35mm and 90mm look good. But at those apertures, I'd rather get the CV offerings. I don't understand their strategy here.

Gabriel, I think you just explained it. IMO, the strategy might be to fill the niche of slower, but compacter lenses; for those customers who do not want CV but red dots. As I am concerned, the 90 Summarit only could interest me. If.
Didier

 

[awilder]

I've not read many enthusiasic comments on the CV f/2.5 offerings in 35 and 50. I have read the CV 50 is a little flat in it's rendering.

 

[Finder]

Hi Nemo,
Thanks for the post, though I can't read those MTF graphs; can you (or anybody else) explain or translate them?
The "practical experience" report is interesting indeed. I find the picture too clinical, digital ... or cligital... besides I wonder why the photographer shoots only at f4 - 5.6, even for a close portrait. How about wide aperture (2.5-2.8)? Just wonder.

The MTF plots show there is nothing really wrong with the lenses. They will work well. How they work pictorially in specific conditions is unknown. MTF is more of a diagnostic tool for the optical designer than anything else. Although they seem to be used as a sales tool as well.

 

[Nemo]

In terms of sharpness, you have more than 50% of contrast for 40 lp/mm wide-open for all lenses at the center of the frame, with a very uniform rendition in the borders and corners. In particular, the 75mm Summarit is impressive. The performance at f/5.6 is outstanding for all lenses. Very good.

These Summarits aren't "poor" M lenses. They are just as powerful as the best Summicrons are, but giving 2/3 stops.

 

[peterm1]

For Marc A - How to read these MTF curves. Once you get the hang of it, its not too hard.

On the vertical axis is a measure of resolution. The higher the curves are up the scale on the graph, the better.

On the horizontal scale is distance in millimeters. This represents the radius from the centre of the image. As lenses tend to be sharpest in the centre and less sharp at the edge this measures this issue. Thus at the far left it shows you the resolution in the centre of a photo and 12 (for example) shows the resolution 12 mms out from the centre etc.

The different curves on the graph show the resolution for different types of image - from fine to coarse (I think thats how it goes - guys help me I am a little rusty here)

And of course to top it off there are different MTF graphs for different aperture settings - one wide open in this case and one stopped down a couple of stops. As you can see when the lens is stopped down, the curves all move up the graph a bit showing that stopping down improves image quality as is normally the case with most lenses.

Broadly speaking if all of your curves on an MTF graph are close together, near the top and fairly flat (bearing in mind that most will drop off towards the right hand side) the better the lens resolution will be at all points on the picture image. Where the curve dips down the image quality will suffer a bit.

In this case I would say that these lenses are very good indeed. It is often the case that modestly specified lenses (ie modest maximum aperture) eat their more trendy fast lens cousins for breakfast - I suppose they are easier and hence cheaper to design and build and do not need expensive "tricks" like aspherical elements to compensate for abberations that fast lenses have in abundance.

 

[Mazurka]

I've not read many enthusiasic comments on the CV f/2.5 offerings in 35 and 50. I have read the CV 50 is a little flat in it's rendering.

Funny. The messages I read tend to complain about the 50/2.5 being "too contrasty."

OTOH, the Voigtlander 50/1.5 and 35/1.7 being so affordable, just get those if you don't like the slower siblings. Super-glue an adpater if you must have them in M-mount.

 

[Mazurka]

... do not need expensive "tricks" like aspherical elements to compensate for abberations that fast lenses have in abundance.

Aspherics have become much cheaper to produce these days, with molded elements and what not. It's hard not to find an aspheric element in a current digicam or even the cheapo kit lens of a DSLR.

Aspherical elements are nothing magical. One such surface simply does the job of two spherical surfaces in correcting aberrations. In this age of computer-aided design and manufacture, I'd say it's a cost-saver more often than not.

 

[Nemo]

The problem is that Leica's designs use quite few elements, and the tolerances in manufacturing are very, very severe. Including an ASPH element into a Leica design makes the manufacture much more complex. Moreover, Leica's glasses are expensive and very difficult to shape. Cheap ASPH elements can be done, but high quality glass ASPH shaped is very difficult.

 

[oscroft]

Funny. The messages I read tend to complain about the 50/2.5 being "too contrasty."

Yes, my CV 50/2.5 is contrasty and sharp, as is my 35/2.5 - if I had to come up with one word to describe them, "flat" is probably the last word I'd think of.

 

[Freakscene]

>can you (or anybody else) explain or translate them?

Here's how to do it yourself and interpret what they mean.

http://www.luminous-landscape.com/tutorials/understanding-series/lens-contrast.shtml

Marty

 

[Marc-A.]

Many many thanks Peter, your explanation is very useful!
Marty, thanks for the link!

The MTF plots show there is nothing really wrong with the lenses. They will work well. How they work pictorially in specific conditions is unknown. MTF is more of a diagnostic tool for the optical designer than anything else. Although they seem to be used as a sales tool as well.

You speak my language, Finder ... that I understand ;-)

 

[Marc-A.]

Yes, my CV 50/2.5 is contrasty and sharp, as is my 35/2.5 - if I had to come up with one word to describe them, "flat" is probably the last word I'd think of.

I agree with you (at least about the Skopar 35, because I've never used the Skopar 50).

My 35/2.5 is sharp enough, contrasty but not too much ... as a matter of fact, it's less contrasty than my Rigid Summicron. Nothing to complain about then.

 

[sepiareverb]

...The 35mm and 90mm look good. But at those apertures, I'd rather get the CV offerings. I don't understand their strategy here.

If the CV 75/2.5 is any indication I think the Summarits are going to be miles above the CV 2.5's in quality. From what I've seen & been reading these seem to be competing with the ZM's.