The 75mm Focal Length

[wda]

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57 minutes ago, stephengv said:

Wow. this is really sharp. 

Agreed. But also note the extremely shallow depth of sharp focus. The iris already shows some loss of sharpness. This is not a criticism,  just an observation and one which leads to the need for some degree of reduced lens aperture to include eye features within the band of sharpness. .

[lct]

1 hour ago, pippy said:

Out of curiosity; was the focus point at minimum focus and (pardon my ignorance) is the min/focus the same for both lenses?

Both at about 1m if i remember well. MFD is 0.7m on 75/2 apo and a bit less than 0.8m on 75/1.4 v2. 

[Sjz]

This thread is enlightening and making me think.

lct, thank you for the comparison, am beginning to suspect I should be looking at the Summicron and not the Summilux as a couple of cms dof is narrow enough for me.  (Or maybe learn how to better use the lens’ I have).

I feel my use of my lens is crude.

1. wide open (or as close to, as max shutter speed allows).

or

2. f8 to f11 if I want a good depth of field and it does not reduce shutter speed too low.

Between ‘wide open’ and f8 is only used for max shutter speed control.  (I only use the 50 APO and the 28 ‘lux).

I remain close to the foothills of the learning curve.

 

[Steve Caddy]

On 1/3/2021 at 2:10 PM, Likaleica said:

The Summarit is, in my opinion, excellent and as sharp as the apo-summicron.  It's light-weight and the 2.4 version has significant improvements over the 2.5, especially the lenshood which comes with the lens.  Love this lens.

I have the 2.5 and love it. It’s surprisingly good. What was improved in the 2.4?

[adan]

0.1 f/stop, and closer focusing. Same glass.

[logan2z]

21 minutes ago, adan said:

0.1 f/stop, and closer focusing. Same glass.

The 2.4 also included a hood and a leather case, although not an improvement in the lens per se.  

[Kl@usW.]

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vor 1 Stunde schrieb Steve Caddy:

I have the 2.5 and love it. It’s surprisingly good. What was improved in the 2.4?

Erwin Puts wrote in his meticulous description of the the 2,5 Summarits that they are  more 2,4s and Leica named them 2,5 to be on the safe side.  So my idea is that the optics are just the same with a different solution hood-wise and the leather case instead of the pouch. 

[pippy]

1 hour ago, adan said:

0.1 f/stop, and closer focusing. Same glass.

Apparently (from what I've read) the actual max f-stop actually didn't change from the 2.5 to the 2.4 but the '2.4' designation was considered convenient by Leica to differentiate, nominally, the two versions. The closer MFD was the real improvement.

Oddly enough I actually much prefer the screw-in hood style of the 2.5 over the slide-out version but accept that am in the minority!

I'll try to find my source for the max-aperture thing but it was certainly something from Leica themselves otherwise I wouldn't have given it any credence...

Philip.

EDIT : I see that Kl@usW. and I were typing the same thing at the same time! Thanks for saving me the trouble of discovering it was Erwin Puts himself who said so.

Edited January 6, 2021 by pippy

[adan]

Only Leica users would count leather cases, and the inclusion/exclusion of lens hoods, as "lens improvements."

And yes, Leica often (but not always) overdesigns the glass diameter, and then sets the actual max. aperture with the blade mechanism, for more precision and consistency.

See the many "I can see the aperture blades in my 35 Summicron ASPH set to f/2!!?" threads.

[pippy]

4 hours ago, Sjz said:

...lct, thank you for the comparison, am beginning to suspect I should be looking at the Summicron and not the Summilux...

I wish lct had never posted the results of his findings!....or am I secretly delighted?............

As mentioned earlier in the thread (post #15) I have a Summarit whose performance is, IMO, faultless. It really is a stellar lens in all respects. But as mine is the f2.5 version there have been occasions where the closer min-focus of the f2.4 would have been welcomed. So my thoughts had been straying towards picking up a Summilux to give me both tighter framing with the closer MFD and better separation with the extra 1.5 stops. I would still hold on to the Summarit because of its size, weight and so on for when I was travelling light.

Now, though, having seen how the Summilux and Summicron performed in lct's test I have to say I prefer the performance of the Summicron. Furthermore the Summicron isn't that much larger nor heavier than the Summarit. So it's now a case of "Summarit and Summilux or Summicron only?"

Bugger-it. Some serious thought needed, methinks.

Philip.

Edited January 6, 2021 by pippy

[adan]

10 hours ago, lct said:

DoF rendering of 75/1.4 v2 and 75/2 apo. Déjà vu sorry but useful IMO.

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

I quote lct's post again so the image is on this page of the thread as well. Because it shows several interesting points about optics in general, as well as the specific 75mms.

1. Yep, the 75mm Summilux shows slightly more apparent DoF than the Summicron, even at f/1.4. The upper "2" and the fine lines thereabouts have sharper edges than as imaged by the Summicron.

This stems from the Summilux having spherical aberration. In effect the spherical curvature of the lens at the outer rim focuses in one plane, while the center of the lens focuses in another plane, and the concentric areas of the lens in between focus on planes in between. This is basically "focus stacking" - done by the glass rather than post-processing.

https://en.wikipedia.org/wiki/Spherical_aberration

(A side note on real-world lens production. Spherical lens surfaces are actually a lousy way to make lenses, because they inherently cause spherical aberration. They are however much easier and cheaper to make than ASPH surfaces - at least before 1992 or so, when precise press-molding of non-spherical (aspherical) surfaces was developed. And the mathematics of a constant-radius (spherical) lens are easier to calculate. So for about 99% of the existence of man-made lenses, they were made with spherical surfaces (at least approximately). But lens designers eventually began combining multiple elements of different glasses in part to correct the problem (and in part to correct other aberrations).)

2) I rather like using fast teles with a little such spherical "focus stacking" with rangefinder cameras. It is more accomodating to mis-focusing in fast-moving situations - one gets a wider range of "sharp enough to use."

3) It also creates a smoother transition from sharp to fuzzy. Some people like a more abrupt focus fall-off, but I think that is part of what contributes to the "clinical" label on some (not all) modern ASPH lenses. At any rate, a question of taste and not "good" or "bad."

4) Spherical aberration usually also causes "focus shift" - as one stops down and removes some of the abberant rays, the plane of "best focus" shifts forward or backwards. Yet the Summilux 75 manages to avoid significant focus shift (at least between f/1.4 and f/2.0). Maybe one of the reasons Dr. Mandler apparently considered the 75 Summilux one his best designs.

More generally...

5) This shows that theoretical DoF calculated for an "ideal lens" can be misleading when one uses real-world lenses. It pays to know one's tools.

6) It is also a nice illustration that DoF extends approximately twice as far into the background as it does into the foreground (compare the front and back 1s and 2s). if you want a range of, perhaps 1.5 m to 3m to appear sharp with a 50mm lens at f/16 - you need to focus at about 1.9m, not halfway between 1.5m and 3m (i.e. 2.25m).

[Mark T]

The 75mm Summicron is great. It was Leica's showpiece lens of it's day (similar to the 50mm APO ASPH Summicron is today), throwing all they could to achieve highest possible performance across the full range of apertures, distances etc.

As has been mentioned in the thread already, the optical design of the 2.5 vs. 2.4  Summarits is unchanged. However, the mechanical design was changed to allow the lens to focus closer. One way of looking at this is that initially, with the 2.5 version, Leica maintained the best possible image quality by limiting the minimum focus to 90 cm. In my opinion, the change to 2.4 Summarits was an attempt to generate some interest in what was a relatively slow-selling 2.5 line. In so doing, Leica took the opportunity to reduce the 75 mm minimum focus distance from 90 cm to 70 cm for marketing purposes. Note that this also makes the 2.4 version much quicker focusing than the 2.5 version. 

Most lenses are at their weakest at maximum apertures and minimum focus distance. Hence many lenses, like the 75mm Summicron, have floating elements to improve their performance in the near-range. Also why most MTF graphs are recorded with the lens focused at infinity (although we are rarely told exactly what distance the lens is focused at, it stands to reason that it is at the distance the lens performs it's best and it is usually infinity). When you think about it, the 75 mm 2.4 minimum focus distance of 70 cm results in a degradation of image quality that may have been considered unacceptable at the time the 2.5 Summarits were produced. Otherwise the 2.5's would have been 70 cm in the first place? The other possibility is that Leica deliberately limited the initial 2.5 lens to 90 cm so as to protect sales of the Summicron.

Whatever the case may be, the 2.5 version of the Summarit will be easier to focus than the 2.4 version as it covers a reduced focus range over the same 90 degree rotation. Also, the 2.5 Summarit will perform better at 90cm than the 2.4 version does at 70 cm (although performance will be equal at 90 cm). The Summicron has a 120 degree focus rotation so is slightly slower to focus than both Summarits and for most people it will be more accurate as a result. Additionally, the Summicron will perform better in the near focus ranges due to the floating elements which are designed to achieve just that. Comparable MTF charts recorded at infinity do not demonstrate comparable performance at minimum focus distance.

[lct]

At the same aperture, Summilux and Summicron 75 have more or less the same total DoF in my view. The Summilux has just more DoF in the background but less so in the foreground. 

[Likaleica]

8 hours ago, Steve Caddy said:

I have the 2.5 and love it. It’s surprisingly good. What was improved in the 2.4?

Just the things that the subsequent posters said

[pippy]

8 hours ago, adan said:

6) It is also a nice illustration that DoF extends approximately twice as far into the background as it does into the foreground (compare the front and back 1s and 2s). if you want a range of, perhaps 1.5 m to 3m to appear sharp with a 50mm lens at f/16 - you need to focus at about 1.9m, not halfway between 1.5m and 3m (i.e. 2.25m).

Absolutely. My class at college was taught the "One-third-In" rule-of-thumb for obtaining best-spread of DoF very early on in the course.

Philip.

[250swb]

I don't use the 75mm very much so chose a Voigtlander f2.5 Skopar after hearing good reports about it. It is a stellar lens and I've not ever been disappointed in it. As an aside the week after I got it Sean Reid did a back to back test between it and the Summarit f/2.5 and his conclusion was that there is so little difference the choice between them was down to very minor preferences in rendering, and of course the price.

[Keith (M)]

10 hours ago, pippy said:

 

Now, though, having seen how the Summilux and Summicron performed in lct's test I have to say I prefer the performance of the Summicron. Furthermore the Summicron isn't that much larger nor heavier than the Summarit. So it's now a case of "Summarit and Summilux or Summicron only?"

Bugger-it. Some serious thought needed, methinks.

Philip.

Might be worth awaiting the outcome of this thread before making a decision!

[pippy]

Ermmm.....Thanks, Keith!.......I think............

Curious! And, yes, food for thought. I don't need a different 75mm but, having seen the results of lct's tests, I did find myself scouting around the 'net...

Perhaps a bit more thought is required before a final decision is made.

Philip.

[Sjz]

4 hours ago, Keith (M) said:

Might be worth awaiting the outcome of this thread before making a decision!

I find myself in a similar position to Philip, more thought before final decision and scouting around the ‘net.  

Need to be careful and keep the wine consumption low.....

 

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[MrFriendly]

On 1/2/2021 at 6:42 PM, stephengv said:

Contemplating of getting a 75mm Lens, most likely the Summarit.
 

How useful is this Focal Length ? Is it versatile?

I think the 75mm is one of the most underrated and one of the least popular focal lengths when compared to the 28/35/50.

Life is too short, get the 75 Noctilux.