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WA lens in Pentacon Six mount?
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PostPosted: Fri Sep 16, 2016 6:24 pm    Post subject: WA lens in Pentacon Six mount? Reply with quote
Hi,
is there in your opinion a good wide angle lens, say between 20mm and 35mm DSLR equivalent, in Pentacon Six mount you can recommend me?

The idea is to used it on my Nikon camera coupled with a Pentacon Six to F mount shift adapter for architectural photography.

Thanks.


PostPosted: Fri Sep 16, 2016 7:21 pm    Post subject: Re: WA lens in Pentacon Six mount? Reply with quote
wolan wrote:
Hi,
is there in your opinion a good wide angle lens, say between 20mm and 35mm DSLR equivalent, in Pentacon Six mount you can recommend me?

The idea is to used it on my Nikon camera coupled with a Pentacon Six to F mount shift adapter for architectural photography.

Thanks.

I have a 50mm CZJ Flektogon, that's around 28mm in 135 terms if you consider the diagonal field of view. I think that's the widest lens in P6 mount. Or perhaps there's also a Russian 45mm, I don't know. Anyway, the Flek is a good lens on film, but I haven't used it on digital. There's also the 30mm Arsat/Zodiak which is also good for what it is, but it's a fisheye.


PostPosted: Fri Sep 16, 2016 8:14 pm    Post subject: Reply with quote
The CZJ Flektogon 50mm F4 is equivalent to 28mm in 35mm format. Do not get too excited in adapting MF lenses to smaller formats. Once I made a comparison between the Pentacon 50mm F1.8 and the CZJ Flektogon 50mm F4. At F4, the Pentacon was clearly sharper than the Flektogon in the corners.

This site describes all the wide-angle lens ever built for the Pentacon Six:
http://www.pentaconsix.com/lenstest.htm


PostPosted: Fri Sep 16, 2016 10:49 pm    Post subject: Reply with quote
But I suppose this is not what he/she originally wanted? A 50mm MF used on a 135 still gives you a 50mm angle of view, which I think is not for architecture photography. I think what is looked for is a 'real' 20-35mm lens. BUt unfortunately, as far as I know there are only the Arsat/Zodiac fisheyes available.


PostPosted: Fri Sep 16, 2016 11:00 pm    Post subject: Reply with quote
Why there are no wide angle FF lenses for crop sensor? Because the angle of view decreases when lens is used on smaller sensor. I.e, using 50/4 P6 on FF 24x36 camera, angle of view is equivalent to about 100mm lens for FF. There aren't any P6 lenses that give "wide angle" to FF 24/36...even the 30mm fisheye angle of view on FF equivalent to view given by 60mm FF lens...


PostPosted: Sat Sep 17, 2016 4:24 am    Post subject: Reply with quote
Used PC Nikkor 35mm or 28mm.


PostPosted: Sat Sep 17, 2016 4:37 am    Post subject: Reply with quote
visualopsins wrote:
Why there are no wide angle FF lenses for crop sensor? Because the angle of view decreases when lens is used on smaller sensor. I.e, using 50/4 P6 on FF 24x36 camera, angle of view is equivalent to about 100mm lens for FF. There aren't any P6 lenses that give "wide angle" to FF 24/36...even the 30mm fisheye angle of view on FF equivalent to view given by 60mm FF lens...


This is not quite correct I'm afraid. When we talk about "equivalent" view we are alway using the 135 system as our reference, since we are most familiar with it. In this sense, given the same focal length, a lens has a "longer" equivalent on a crop camera, compared with a 135 camera - this is correct. Similarly, this same lens (if mountable) would look "wider" on a medium format camera, yet it doesn't hold vice versa. A 50mm MF lens, using the 135mm system as reference, is still a 50mm lens, though it is safe to say that a 50mm on FF looks like a 100mm on a MF. If you want to know "absolutely" how wide a lens is, ie without referencing any system as "equivalent", there a parameter called "angle of view". The table in Gerald's link gives a bunch of perfect focal length pairs as well as excellent explanations.


PostPosted: Sat Sep 17, 2016 10:03 am    Post subject: Reply with quote
This is difficult, and I dont even own the Zodiac which is said to be one of the cheapest 6 wideeye.

You could reevaluate your approach or perhaps use a 50mm or 45mm P6 lens with one of these screw-on wideners. Even if you find one with the right thread diameter it is going to be not very wide (the HQ wideners are 0.8 and 0.7, the common 0.5 ones are junk.)


PostPosted: Sat Sep 17, 2016 10:31 am    Post subject: Reply with quote
buerokratiehasser wrote:
This is difficult, and I dont even own the Zodiac which is said to be one of the cheapest 6 wideeye.

You could reevaluate your approach or perhaps use a 50mm or 45mm P6 lens with one of these screw-on wideners. Even if you find one with the right thread diameter it is going to be not very wide (the HQ wideners are 0.8 and 0.7, the common 0.5 ones are junk.)


Thanks for the tip. Never heard of wideners, can you give me some pointers?


PostPosted: Sat Sep 17, 2016 10:33 am    Post subject: Reply with quote
calvin83 wrote:
Used PC Nikkor 35mm or 28mm.

Yes, that would be the next option.

The PC 28mm f3.5 seems to be a very good lens. It can be found for 300-350$, so in principle not so expensive.
Thanks.


PostPosted: Sat Sep 17, 2016 11:54 am    Post subject: Reply with quote
Well, it's the opposite of a teleside converter. I am sorry if I did not find the right term.

You screw these on the front of the lens and its focal length reduces by 0.8 or 0.7 or whatever. But most of these are junk as I said. You would need a good one like Sony VCL and from these one that fits your lens thread. Also wideners in this range (not the toys for video cameras) are pretty unwiedly with much glass, so the additional problem would be the tear on the shift adapter.


PostPosted: Sat Sep 17, 2016 12:30 pm    Post subject: Reply with quote
Jiaming wrote:
visualopsins wrote:
Why there are no wide angle FF lenses for crop sensor? Because the angle of view decreases when lens is used on smaller sensor. I.e, using 50/4 P6 on FF 24x36 camera, angle of view is equivalent to about 100mm lens for FF. There aren't any P6 lenses that give "wide angle" to FF 24/36...even the 30mm fisheye angle of view on FF equivalent to view given by 60mm FF lens...


This is not quite correct I'm afraid. When we talk about "equivalent" view we are alway using the 135 system as our reference, since we are most familiar with it. In this sense, given the same focal length, a lens has a "longer" equivalent on a crop camera, compared with a 135 camera - this is correct. Similarly, this same lens (if mountable) would look "wider" on a medium format camera, yet it doesn't hold vice versa. A 50mm MF lens, using the 135mm system as reference, is still a 50mm lens, though it is safe to say that a 50mm on FF looks like a 100mm on a MF. If you want to know "absolutely" how wide a lens is, ie without referencing any system as "equivalent", there a parameter called "angle of view". The table in Gerald's link gives a bunch of perfect focal length pairs as well as excellent explanations.


Thank you. Smile However, I do not understand it yet.

The "crop factor" for 135 format, using 6x6 system as reference, is 1.83. Thus 30mm 6x6 lens on 135 camera has same angle of view as 30mm * 1.83 = 54.9mm lens for 135 format. (<-- EDIT!: should be "for 6x6 format.")

I have a 90mm MF lens for Pentax 6x7. The "crop factor" for 135 format, using 6x7 system as reference, is 2.02. When mounted on 135 system I expect the same angle of view as 90mm * 2.02 = 198mm lens for 135 system. (<-- EDIT!: should be "for 6x6 system.") Therefore with 135 camera I will make a photo using 90mm 6x7 lens, and another photo using 200mm 135 lens. Both photos should have the same angle of view if I am correct (<-- EDIT!: and I would be wrong!) Laughing, according to my calculations:



Last edited by visualopsins on Sat Sep 17, 2016 10:24 pm; edited 1 time in total


PostPosted: Sat Sep 17, 2016 1:32 pm    Post subject: Reply with quote
Would it perhaps be possible to shorten the shift adapter?
aka implicit speedbooster


PostPosted: Sat Sep 17, 2016 10:08 pm    Post subject: Reply with quote
visualopsins wrote:

The "crop factor" for 135 format, using 6x6 system as reference, is 1.83. Thus 30mm 6x6 lens on 135 camera has same angle of view as 30mm * 1.83 = 54.9mm lens for 135 format.


When we talk about "crop factor", we automatically assume the larger format as reference. Say when a 35mm FF lens used on a APS-C camera, the angle of view would be like using a 35*1.5 (or 1.6) ~50mm lens in the larger FF system.
Similarly, we can surely talk about the crop factor between medium format and 135 format, then again we'll have to use the larger medium format as reference. Your calculation are correct - we should indeed multiply 30mm by 1.83, but it would be more correct to say that "the angle of view of a 30mm MF on a 135 camera, is equivalent to that of a 54.9mm MF on an MF camera", which is more analogous to the comparison between FF and APS-C. The larger one is always used as the reference!
Does anybody here have better explanations? Rolling Eyes I know it's tricky to think about this question..


PostPosted: Sat Sep 17, 2016 10:19 pm    Post subject: Reply with quote
Jiaming wrote:
visualopsins wrote:

The "crop factor" for 135 format, using 6x6 system as reference, is 1.83. Thus 30mm 6x6 lens on 135 camera has same angle of view as 30mm * 1.83 = 54.9mm lens for 135 format.


When we talk about "crop factor", we automatically assume the larger format as reference. Say when a 35mm FF lens used on a APS-C camera, the angle of view would be like using a 35*1.5 (or 1.6) ~50mm lens in the larger FF system.
Similarly, we can surely talk about the crop factor between medium format and 135 format, then again we'll have to use the larger medium format as reference. Your calculation are correct - we should indeed multiply 30mm by 1.83, but it would be more correct to say that "the angle of view of a 30mm MF on a 135 camera, is equivalent to that of a 54.9mm MF on an MF camera", which is more analogous to the comparison between FF and APS-C. The larger one is always used as the reference!
Does anybody here have better explanations? Rolling Eyes I know it's tricky to think about this question..


Embarassed Thanks so much for that, I get it now...your first sentence was enough! Very Happy


PostPosted: Sat Sep 17, 2016 11:35 pm    Post subject: Reply with quote
visualopsins wrote:


Embarassed Thanks so much for that, I get it now...your first sentence was enough! Very Happy


No problem! Happy Dog
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