75mm APO depth of field

[lct]

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If I do some photos with the Summicron 90 and with the 75 Apo, in those with the 90 the subject seems to fall more easily into a zone of depth of field (or "appears" to fall), especially if I shot with a certain diagonal and not flat to the subject.

May i ask if you did your comparisons in RF or LV mode? Just curious as i did not notice significant differences between my 90/2 apo and 75/2 samples DoF wise so i wonder if RF accuracy may play a role in your findings.

[Al_OOF]

I have only M9. I take into account also the short focus of the 75 but after many photos with the two lenses you can "extract" a feeling but I will try to confirm or not with some, more specific test.

Perhaps the Summicron 90 II is different from the 90 Apo...

[lct]

If you look at the depth of field @ F16 marked on the current 75mm Summarit focussed @ Infinity you will see that it is 8 meters to Infinity. The equivalent depth of field on the 75mm Summicron is approximately 10 meters to Infinity. A significant reduction.

Difficult to say given the lack of 8 meters marking on the 75/2 but both DoFs look very similar if not identical according to Leica's technical datas.

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[NB23]

Simple mathematical formulas only hold for ideal models.

In the simplified vision all 75mm naturally have the same properties.

 

The ideal model is not buyable in the real world, so the mathematical formulas should be extended, and then they are not simple any more.

 

Not to speak of tolerances in the real world.

Jan

 

That's why some 75 crons are as luminous as noctiluxes and others are as slow as f4, yes?

It's a gamble.

 

It is also safe to say that the tolerances are so loose that a some 75 crons can weigh up to double its standard weight, depending on who assembled them at the factory. Yes?

 

As usual, this Leica conversation has gone into such extreme nitpicking with incredible misinformations shown as the truth, where lens aberrations become "magic", where softness become "a Mandler masterpiece" and where a regular performing 35 cron that shows quite insane shift in its field of focus that gets called "the bokeh king". Really???

 

According to this thread, one is almost to believe that lens manufacturers are idiots who have no clue about lenses. How can they even go as far as to call the 50mm summilux asph line lenses a... 50mm summilux asph? It could well be a 35mm lens and sometimes a 75mm lens, depending on the tolerances of the machines that day and the assembly dudes on any given day.

 

Enough with this BS, guys. A 75 mm f2 cannot exhibit shallower depth of field then a 85 f1.4. Just can't. There are variations in tolerances from one lens to another but not as far as to make a 75 cron into a noctilux f0.95... Or to be more realistic, into a 75mm f1.2, because that's what it would take to make a 75mm lens equal, and even beat a 85 1.4.

Insane.

[pgk]

Insane.

A forum is a meeting place for the discussion of questions of interest. If you aren't interested in such discussions there is no need to take part. Simply decrying other's opinions, observations and evidence by exaggerated statements is hardly a positive contribution, especially when you are wrong:D.

[jankap]

 

"That's why some 75 crons are as luminous as noctiluxes and others are as slow as f4, yes? "

No.

 

"It is also safe to say that the tolerances are so loose that a some 75 crons can weigh up to double its standard weight, depending on who assembled them at the factory. Yes? "

No. Leica is so "expensive", because they have to work with small tolerances. That is - perhaps not the only reason -, because of the rangefinder principle.

 

"As usual, this Leica conversation has gone into such extreme nitpicking with incredible misinformations shown as the truth, where lens aberrations become "magic", where softness become "a Mandler masterpiece" and where a regular performing 35 cron that shows quite insane shift in its field of focus that gets called "the bokeh king". Really???"

In the last part of the Zeiss article the author explains, why mathematics is not the only measure.

 

The DOF marks on the lenses have a mathematical background. I´ll check this.

 

For example there are lenses with APO design, while others are not.

So, some lens designs are sharper than others. It is possible, that the impression of DOF sharpness in the wall chart picture is different.

 

But the 75mm seems to be a remarkable lens, I feel an attack of GAS coming.

Jan

[lct]

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There are variations in tolerances from one lens to another but not as far as to make a 75 cron into a noctilux f0.95

Both 75/2 and 50/0.95 lenses have almost the same DoF at full aperture though.

[NB23]

Both 75/2 and 50/0.95 lenses have almost the same DoF at full aperture though.

 

Many errors, one would argue.

First, you are basing your facts on a dof calculator that has been proven invalid many times over in this thread.

Then, a 50 isn't a 75. But both could be a 66, thanks to regular tolerance errors.

 

And then there is the high probability that a 75 cron actually shows even less DoF then a noctilux, because, remember, the micro-contrast can play a role as well as other obscure reasons... Therefore a 75 cron is more likely matching (and not against all odds) the yet unexisting Noctilux f0.7 double asph.

[NB23]

Think about it: given that it bests a 85 1.4, it must at least match a 50 f0.7.

 

I'm aimply going by the (il)logic from this very enlightening thread.

[jankap]

Some samples

Canon 28mm (of 1970)

f/5.6, 3 meters: DOF from 1.75 to 10 meters

f/8, 2meters: DOF from 1.2 to to 6 meters

Leica 35 mm (of 1996)

f/5.6, 3 meters: DOF from 2.1 to 5.6 meters (estimated)

f/8, 2 meters: DOF from 1.45 to 4 meters (estimated)

Leica 50mm (of 1950)

f/5.6, 3 meters: DOF from 2.5 to 4 meters

f/8, 2 meters: DOF from 1.7 to 2.5 meters

Canon 135mm (of 1980?)

f/16, 15 meters DOF from 10 to 30 meters (estimated)

 

Estimated means, that the distance scale is not detailed enough.

 

With a DOF calculator set at COC of 0.033mm:

28mm fits exactly

35mm fits more or less according to the estimated distances

50mm fits very good

135mm fits more or less according to the estimated distances

 

I think, we can conclude that the DOF scales are calculated (mathematics).

If the 75mm shows a different behavior, by comparing printed pictures, there must be another reason.

Jan

[CheshireCat]

Amazing how this discussion (based on the laws of physics!) is still based on the fact that the focus field is flat.

 

Most people in the past (based on the laws of physics!) also thought the earth was flat

 

About DOF tables and engravings on the lens, these are probably valid on the axis only. In any case they are useless for this discussion (and not only).

[Jennifer]

Just out of interest can anyone, with experience of both lenses, tell me how the depth of field of the 75mm APO-Summicron at f/2 compares with that of the last version 75mm Summilux at the same aperture? Personally, I find the Lux extremely shallow at f/1.4, only very marginally deeper at f/2 and actually focusable with accuracy by f/4. Though maybe when Leica finally get around to CLA my lens that might all change.

[Michael Geschlecht]

Hello LCT,

 

Thank you for your response.

 

It would appear that there is at least 1 error in the depth of field graphs supplied by Leica which are displayed above in your Post #43.

 

If you look @ the actual Summarit F2.5 photo it shows the depth of field @ F16 with the lens set @ Infinity to be 8 meters to Infinity. The graph says 10.7 meters to Infinity.

 

If you look at the photo of the Summicon F2 the photo APPEARS to show a depth of field of approximately 10 meters to Infinity. The graph shows 10.7 meters to Infinity.

 

If you re-read my Posts #'s 20, 23 & 24 above this will explain why there is a difference between the 2 lenses as shown in Leica's photos

 

You might also better understand the situation if you would pop up photos of the 280 F2.8 APO showing its depth of field scale with the lens focussed to Infinity & its 280 F4.8 predecessor focussed to Infinity & compare equivalent depths of fields on the lens barrels. If I were more capable with computers myself I would have put these photos here already.

 

Best Regards

 

Michael

[pico]

Amazing how this discussion (based on the laws of physics!) is still based on the fact that the focus field is flat.

 

Thanks for that.

Others might want to explore the Rodenstock Imagon for examples of curved focus planes.

[jankap]

pico, we discuss here about your question without seeing any proofs (=pictures).

 

Perhaps the pictures at the end of the Zeiss article (the repros) give a solution.

A less sharp lens seems to have more DOF.

Jan

[Michael Geschlecht]

Hello Chesire Cat,

 

The depth of field markings on the lens barrels in question ARE what we are writing back & forth about. The charts provided by Leica are in error. Camera manufacturers use the same set of standards for all of their lenses: 1/30 mm circle of confusion.

 

What I have been writing about above has been in the photographic literature well back into the 20th Century.

 

Interestingly: The 75mm F1.4 shows an engraved depth of field of 10 meters to Infinity @ F16 when the len is focussed to Infinity.

 

Best Regards,

 

Michael

[lct]

Many errors, one would argue.

First, you are basing your facts on a dof calculator that has been proven invalid many times over in this thread.

I have no DoF calculator with 0.95 aperture but they just apply DoF formulas which are just what they are my friend. Do you want really one?

[CheshireCat]

Hi Michael,

 

The OP was just expressing a subjective experience.

 

I fail to understand why you (and others) are still basing this discussion on the ridiculous DOF marks on the lens barrels, and Leica diagrams as if they could prove the OP must (or must not) be seeing what he sees.

 

Lens markings are nonsense for several reasons, especially when talking about subjective experience. It's been a while I have been proposing to replace them with latin mottos (each lens model should have its one ).

[lct]

Camera manufacturers use the same set of standards for all of their lenses: 1/30 mm circle of confusion.

I still use this CoC value as a reference for full frame lenses personally but whatever value one chooses, two lenses will always have the same DoF with the same focal length, the same CoC value, the same aperture and the same subject distance in my book which seems to be the same as Leica's in their technical datas at least. OoF rendering, usully called bokeh, is another story.

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Hallo,

Look here: Leica M

[pgk]

OoF rendering, usully called bokeh, is another story.

I suggest that you read the Zeiss pdf I referred to earlier. The two are to a degree interlinked (which if you think about it logically, they must be.

 

Any DoF table makes assumptions regarding the factors which influence 'sharpness' - they should be considered as guidance rather than anything else. They also assume a flat field and lack of imperfections..... here we go again;).