25 vs 28 mtf wise

[Fabian]

I have just compared the mtf graphs of a few zeiss lenses, when I realised that the 25 is a much better performer, at least on the paper.
I know its not all about papers but I am still curious why that is.
Is the 28 an old design or is a 25 easier to design. Or does the 28 do something the 25 can't?

Maybe some of you could tell me?


Fabian

 

[PaulDalex]

I did exactly the same, more in general I base any purchase decision on MTF. Someone here told us that those posted by Zeiss are measured MTF, as should always be the case to be fair to customer.
In the specific case I means that if I ever buy one of the two it will be the 25, the performance of the 28 is a bit disconcerting to me. On the other hand I have the ZM 35, which is a dream come true, a substantial advance of technology for consumer optics. The results remind me of MF and clearly saturate the MTF of the best commercial film. Actually I am less willing to get out with my Fujii 6x9 rather then M5 with ZM 35. the personality is splendid to: its image are airy and transmit a strong sense of space. Far away object have the finest detail I have ever seen in a 35 moderate wide to normal.
But there is another MTF which is even more astonishing. I am staring to save and frankly with such weapons like ZM 35 ZM85 I am afraid the rest of my gear will see little use
Why did Zeiss decide this policy regarding the 28 is a mistery. Evil marketing people perhaps? Even more surprising considering that the Y/C 28 is an excellent lens.

 

[35mmdelux]

28/25 aren't the most challenging of designs as far as I know. The 28 might be an old design.

 

[Dektol Dan]

I own a 28

I own a 28

I find it wonderful! I have been shooting for 50 years and I would say it is among the best of the best. It does have that MF look and it is the perfect compromise between modeling (that 3D look/shadow detail) and higher contrast. All of the newer high contrast lenses look like water colored black and white images. That is because of the misguided use of coatings which cause color refractions, RGB, to balance to white or cancel. The human eye cannot do this so to my eye all of the newer lenses have a very artificial look compared with the older post war lenses.

There is no perfect RGB balance with coatings and the Biogon leaves a blue cast which I found very discomforting at first. When I realized that this blue carried the modeling/3D component I finally mastered it. Only the Leitz ASPH Summilux lenses can better it, and nothing from CV that can match its modeling.

 

[Turtle]

I own a biogon 28, 35 and 50 planar:

the 28 is in no way inferior in practical use. I bought it knowing the MTF was inferior to the 25 but with the following factors in mind:

I get to use the 28 framelines in my Leica 0.72
The lens is quite a bit smaller and lighter than the 25
The lens is cheaper than the 25

As I say, performance is superb and plenty good enough for me, although as the MTFs say, the 25 is better on MTFs. I justs did not want to go down teh road of external finders, extra size and cost.

Just dont go thinkning the 28 is a duff lens....it is superb in fact...many likening it in performance to the new Elmarit M 28 2.8.

 

[Terao]

As I understand it the 25 is the older of the two designs, dating back to pre-WW2 Zeiss lenses. Of course updated but essentially the same.