28/3.5 & 25/4.0 Skopars

[Matus]

I plane to use a 35 or 40 lens as my main one on my R3A (I am still not sure whether I should have got R2A with the 35/2.5 skopar, whatever) and later get a longer (presumably 75/2.5) and also wider. But the wider end is a bit of problem.

One one hand the skopar 28/3.5 seems like a very good lens but I am worried that it could be too close to 35/40 lens. Also the 28 is available in Chrome which I would probably prefer.

On the other hand the 25 lens would couple very well with the 15 I would like to get later.

So I ask - how does the performance of this two skopars - 25 & 28 compare? I will need an external viewfinder anyhow so this does not play a role (I am too far from getting the Zeiss Ikom ZM).

 

[ferider]

28, 40, 75 works very well on the R3*. Advantages are (1) available and relatively cheap outstanding 40mm lenses - 40/2 Summicron or Rokkor, 40/1.4 Nokton, 40 Sonnar, (2) 28 mini-finder and (3) isolated 75mm framelines, a great body for the 75/2.5, for example. And, everybody knows how much I like the 28/3.5 or 28/1.9 🙂

Cheers,

Roland.

 

[raid]

I just posted in another thread that I love my CV 25mm/4. It is a super lens overall.
As for the Bessa camera, I have the Bessa R, T, and l. The Bessa R VF is awesome.

 

[Rob-F]

I plane to use a 35 or 40 lens as my main one on my R3A (I am still not sure whether I should have got R2A with the 35/2.5 skopar, whatever) and later get a longer (presumably 75/2.5) and also wider. But the wider end is a bit of problem.

One one hand the skopar 28/3.5 seems like a very good lens but I am worried that it could be too close to 35/40 lens. Also the 28 is available in Chrome which I would probably prefer.

On the other hand the 25 lens would couple very well with the 15 I would like to get later.

So I ask - how does the performance of this two skopars - 25 & 28 compare? I will need an external viewfinder anyhow so this does not play a role (I am too far from getting the Zeiss Ikom ZM).

I have the 25/4, 28/3.5, and 35/2.5 in LTM mount, and the 40/1.4 in M mount. While 28 and 35 may be a bit close together (at least numerically) I do not think that 28 and 40 are at all too close. Actually, the 28 covers exactly twice the area of the 40.

Here's why: The square root of 2 is approximately 1.414. Now, 1.414 times 28 equals 40. What does this prove? Simply that since the area increases in proportion to the square of an increase in linear dimension, that when we increase the width and height by the square root of two, we have doubled the area. In my mind, that is the ideal relationship between successive lenses.

Leitz thought so too. That's why they made one of their telephoto lenses 280mm instead of 300. That positions it exactly between the 200 and 400--not arithmetically, but geometrically. 200 x 1.414 + 280. And 280 X 1.414 = 400 (approximate and rounded off slightly.)

So: mathematical justification aside, I have found 28-40-75 to be a very good combination.

That said, a similar square root of two relationship exists between 25mm, 35mm, and 50mm. And I do use 25 (or 24) 35, and 50 as a very useful three-lens combination as well. Or, 25-35-50-75 as a four-lens outfit. The relationship between 50 and 75 is also closer to the square root of two principle than 40 and 75 is.

So since you want to include a 15 eventually, and would like to space the next wide angle closer to the 15, I think maybe the 25-35 (and 50 if you want) sequence is better for you than the 28-40 one.

 

[ferider]

This is a nice way to look at the sqrt(2) rule that Rob explained:

Take a landscape oriented photo with 28. Turn it around, to portrait format. The short side of the 28mm frame is as long as the long side of the 40mm frame. Or: a 28mm landscape picture is put together from two 40mm portrait oriented pics.

🙂

 

[Matus]

Thank you for your opinions. Indeed - it will not be an easy choice. Lucky me I will only have to make in next year 🙂

Rob-F - you are indeed correct with you mathematics. I myself was surprised when I for the first time computed how does the linear size (not the area) - at given distance - of the image depends on the focal length. Linearly! This is true even for the wide angle lenses. But still - the feeling that given focal length is indeed different - especially with the wide lenses.

As an example of the above - let me take following "step factors":
~ 1.4 (difference between 28 and 40)
~ 1.6 (difference between 25 and 40)
~ 1.9 (difference between 40 and 75)

starting from 40 mm lens, one would end up with following setups (approx.):
F = 1.4: 15, 21, 28, 40, 56, 80
F = 1.6: 15, 25, 40, 66, 110
F = 1.8: 12, 21, 40, 75, 135

I find it interesting that while most people would be fine going from 40 to 75 or even 90, going wide the step from 40 directly to 21 like too wide. What is your experience?

Anyhow - if you were considering 15/4.5 - what would be your next lens - 21, 25, or even 28?

 

[35mmdelux]

Rob-F, great explanation. THKS -

EDIT: I've settled on the 21-35-50 kit for now -

 

[jmilkins]

Some excellent explanations in this thread thank you.

On my R3a, a 28/40/75mm combo feels great. The 28mm seems a great landscape or environmental portrait lens, and its perspective can be kept under control just that bit more easily than the 25mm. My 15mm is there as the super wide and is used a lot - it was my first RF lens and I still love it.