Off the beaten path: 35mm telephoto lenses adapted to 645

[MMfoto]

And this Zeiss Jena Sonnar 180/2.8 was actually initially sold for 35mm, starting with the Contax in the 30s (that's why they call it the Olympic Sonnar), in the 50s for Exakta, Praktina and M42. All had a removable lens mount which was originally from the Contax to add a mirror adapter. Soon 3rd party makers figured out this lens worked well on the Pentacon Six (6x6) and offered adapters (remove the original mount, simple screw, add the new mount).
Since this was popular, Zeiss Jena made it then for a long time natively in the Pentacon Six mount, without the old removable mount.

I have one for my Praktina, and still looking for the adapter to use the same lens easily on my Pentax 645, since this is easy adapted from Pentacon Six. For now I saw the adapter only for stupid prices, but here someone found it cheap: https://blendfx.com/csj-sonnar/

I believe they only sold the original version in Pentacon six mount briefly. The native P66 180/2.8 they sold until around 1991 is an updated formula with slightly larger optics. Both cover 6x6, but the newer version is just a little larger.

 

[aoresteen]

Yes a monster it is but a tripod tames it.

 

[flavio81]

Sorry guys,

Right now the longest medium format lenses are the cheapest.

Pentax 6x7 200/4 lens is the cheapest Pentax 6x7 lens on sale right now.
The 300/4 is also one of the cheapest ones out there.

Most likely the 400 and 500mm Pentax 6x7 lenses are cheaper than their 35mm equivalents.

The Bronica 250/5.6 and 500/8 lenses for the ETR system are also incredibly cheap.

Thus, I don't find the reason to try to adapt 35mm lenses to medium format, assuming they would have the required coverage.

 

[abruzzi]

The Bronica 250/5.6 and 500/8 lenses for the ETR system are also incredibly cheap.

The 500/8 E and EII are pretty cheap, but the PE is pretty expensive.

(Visually it looks like the 500/8 PE, PS, and PG lenses are the same with differing mounts for ETR, SQ, and GS. If that were true and Bronica had made a way to easily move it from one mount to another, I'd consider the price, but $1500+ for each system, is a bit much.)

 

[ant!]

For Pentax 645, 200mm is cheap (dirt cheap) in MF or AF, everything up to 400mm (300/5.6, 300/4, 400/5.6, 100-300/5.6) just a tiny bit more but still very reasonable (the AF versions a bit more then the MF), only the 600/5.6 is more expensive, above $1000 (MF only).

 

[yurihuta]

Sorry guys,

Right now the longest medium format lenses are the cheapest.

Pentax 6x7 200/4 lens is the cheapest Pentax 6x7 lens on sale right now.
The 300/4 is also one of the cheapest ones out there.

Most likely the 400 and 500mm Pentax 6x7 lenses are cheaper than their 35mm equivalents.

The Bronica 250/5.6 and 500/8 lenses for the ETR system are also incredibly cheap.

Thus, I don't find the reason to try to adapt 35mm lenses to medium format, assuming they would have the required coverage.

the appeal is not only the focal length, but the speed of the lenses in 35mm. So adapting a Canon FD 600mm f/4.5 to Pentax 67 is pretty appealing given the speed and the cost of the lens. There is no 300mm f/2.8 available for Pentax 67, but (with patience) you can purchase a Nikon 300mm f/2.8 ED for under $300 USD, much less than a Pentax M* 300mm f/4 - and it is a stop faster. Yes, there is the cost of conversion, but many of these focal length and aperture 35mm telephotos are simply not available in the medium format ranges... until you convert them.

 

[flavio81]

There is no 300mm f/2.8 available for Pentax 67, but (with patience) you can purchase a Nikon 300mm f/2.8 ED for under $300 USD, much less than a Pentax M* 300mm f/4 - and it is a stop faster

But, by any chance, have you tried shooting a pentax 300/4 at f4.0? Depth of field is extremely narrow.

A 300/2.8 used in a Pentax 6x7 would give you the full frame equivalent of about 150mm at f1.0-f1.2 in terms of depth of field. The DOF becomes so narrow that is unusable for practical purposes. Too much of a good thing.

 

[OAPOli]

The DOF of a 300/2.8 lens is the same on 135 or 6x7 or 4x5 but the FOV is different.

Usually, adapting a 135 format lens to medium format lowers the minimum focus distance because of the focal flange mismatch. If you are limited to close-ups, focusing can be be a bit easier (when the subject is still) even though the DOF is narrow.

I've used a 112/1.4 aerial lens on 6x7 and focused it accurately. Maximum focus distance was <1m.

 

[yurihuta]

But, by any chance, have you tried shooting a pentax 300/4 at f4.0? Depth of field is extremely narrow.

A 300/2.8 used in a Pentax 6x7 would give you the full frame equivalent of about 150mm at f1.0-f1.2 in terms of depth of field. The DOF becomes so narrow that is unusable for practical purposes. Too much of a good thing.

I used to own the Pentax 67 M* 400mm f/4, so am familiar with that lens and its ability.

 

[wiltw]

But, by any chance, have you tried shooting a pentax 300/4 at f4.0? Depth of field is extremely narrow.

A 300/2.8 used in a Pentax 6x7 would give you the full frame equivalent of about 150mm at f1.0-f1.2 in terms of depth of field. The DOF becomes so narrow that is unusable for practical purposes. Too much of a good thing.

Cambridge Color DOF calculator says 300mm f/2.8 combination on 6x7 format would

• yield DOF zone of 12.6' at 100' shooting distance, assuming manufacturer standard DOF
• yield DOF zone of 4.3' at 100' shotting distance, assuming 20/20 vision (rather than manufacturer standard DOF)

In comparison, on 135 format, 150mm f/2 yields DOF zone of 5.8' at 100' shooting distance, assuming 20/20 vision and 150mm f/1.4 yields DOF zone of 4.0' at 100' shooting distance.

 

[flavio81]

The DOF of a 300/2.8 lens is the same on 135 or 6x7 or 4x5 but the FOV is different.

I have converted the FOV, thus, "equivalent to 150mm"

I've used a 112/1.4 aerial lens on 6x7 and focused it accurately. Maximum focus distance was <1m.

This is a non-sequitur. I never said you can not focus it accurately. I said that the narrow DOF is not practical. As in, actual usage for normal subjects.

 

[flavio81]

Cambridge Color DOF calculator says 300mm f/2.8 combination on 6x7 format would

• yield DOF zone of 12.6' at 100' shooting distance, assuming manufacturer standard DOF
• yield DOF zone of 4.3' at 100' shotting distance, assuming 20/20 vision (rather than manufacturer standard DOF)

In comparison, on 135 format, 150mm f/2 yields DOF zone of 5.8' at 100' shooting distance, assuming 20/20 vision and 150mm f/1.4 yields DOF zone of 4.0' at 100' shooting distance.

Hi Wilt W !

A DOF calculator uses a circle of confusion(CoC) metric to calculate according to an arbitrarly chosen metric (CoC) that represents an "acceptably focus" print.

The DOF calculator changes circle of confusion when you change format.
So, when you go up from 35mm to 6x7, it enlarges the circle of confusion to compensate, so the "acceptably sharp" metric is equal for all formats.

However in real life, when you are looking at at 6x7 print, you are expecting to find much more detail, more resolution. So the real circle of confusion (CoC) that will determine DOF will be a much smaller CoC, one very close to the CoC used for 35mm.

This means the real, perceived, subjective DoF will be much more narrower than what the calculator reports.

Thus, for my calculation, a 300/2.8 lens on 6x7 format will behave more or less like a 150/1.0 or f1.2 lens on a full frame camera, assuming that said camera has as high a resolution as a 6x7 camera.

 

[wiltw]

Hi Wilt W !

A DOF calculator uses a circle of confusion(CoC) metric to calculate according to an arbitrarly chosen metric (CoC) that represents an "acceptably focus" print.

The DOF calculator changes circle of confusion when you change format.
So, when you go up from 35mm to 6x7, it enlarges the circle of confusion to compensate, so the "acceptably sharp" metric is equal for all formats.

However in real life, when you are looking at at 6x7 print, you are expecting to find much more detail, more resolution. So the real circle of confusion (CoC) that will determine DOF will be a much smaller CoC, one very close to the CoC used for 35mm.

This means the real, perceived, subjective DoF will be much more narrower than what the calculator reports.

Thus, for my calculation, a 300/2.8 lens on 6x7 format will behave more or less like a 150/1.0 or f1.2 lens on a full frame camera, assuming that said camera has as high a resolution as a 6x7 camera.

The acceptable sharp criteria remains the same, but the Circle of Confusion size is altered. Yet the degree of magnification to achieve the same final print size (8x10 standard size for the DOF calculations performed by the Cambridge Color calculator) results using the two FL mentioned (150mm with 135 format, 300mm with 6x7 format) yields the DOF results which I posted. Same print size, same viewing distance are assumed, and the more acute 20/20 vision (rather than poorer vision assumption behind 'manufacturer standard'). The program results are the program results, in spite of your arguments presented.

 

[OAPOli]

I have converted the FOV, thus, "equivalent to 150mm"

I was referring to the "f/1.0-f/1.2" equivalence. I'm not sure why the 135 crop is a gold standard for DOF; the DOF will be natively high due to the low magnification.

For subjects that are not too far and not too close (i.e. hyperfocal distance >> subject distance (d) >> f), the DOF = 2*coc*N*(d/f)^2. N is the f-number.

So, for the same perspective or subject distance; and for the same coc, if you go from f=300 to 150mm, you need to reduce the f/N by four. So 150/0.7 will give you the same DOF on 135 crop as 300/2.8 on 6x7 when the framing is the same (roughly speaking: if you are framing horizontally, the lens should be 130mm). Yet the DOF at d=6m and coc=0.03mm is perfectly workable (IMO) at 6.7cm.

 

[flavio81]

I was referring to the "f/1.0-f/1.2" equivalence. I'm not sure why the 135 crop is a gold standard for DOF; the DOF will be natively high due to the low magnification.

Yes, I agree with you, and in some sense this is part of my argument, 6x7 format will have different usage expectations where greater magnifications will be used, either via larger print size or via more demanding scrutiny by the viewer.

So, for the same perspective or subject distance; and for the same coc, if you go from f=300 to 150mm, you need to reduce the f/N by four. So 150/0.7 will give you the same DOF on 135 crop as 300/2.8 on 6x7 when the framing is the same (roughly speaking: if you are framing horizontally, the lens should be 130mm).

Thus the depth of field will be even narrower than my estimation.

Yet the DOF at d=6m and coc=0.03mm is perfectly workable (IMO) at 6.7cm.

Here I would think that this would make the shot possible if your subject stands very, very still and the camera is fixed on a tripod. Thus my preference for more "practical" (greater) depth of fields .

 

[wiltw]

OK guys, assuming (perhaps false assumption) that medium format lenses deliver twice the detail resolution as 135 format, so that the photographer makes a 16" x 20" print from MF with same grain size on print but twice the detail...if we have a subject at 100'

• 135 format 8x10 print viewed from 10", has 20/20 vision DOF zone of 5.75' when shot with 150mm f/2
• 6x7 format 16x20 print viewed from 20", has 20/20 vision DOF zone of 6.1' when shot with 300mm f/4

 

[reddesert]

I was referring to the "f/1.0-f/1.2" equivalence. I'm not sure why the 135 crop is a gold standard for DOF; the DOF will be natively high due to the low magnification.

For subjects that are not too far and not too close (i.e. hyperfocal distance >> subject distance (d) >> f), the DOF = 2*coc*N*(d/f)^2. N is the f-number.

So, for the same perspective or subject distance; and for the same coc, if you go from f=300 to 150mm, you need to reduce the f/N by four. So 150/0.7 will give you the same DOF on 135 crop as 300/2.8 on 6x7 when the framing is the same (roughly speaking: if you are framing horizontally, the lens should be 130mm). Yet the DOF at d=6m and coc=0.03mm is perfectly workable (IMO) at 6.7cm.

The ratio f/N should be held constant, not change by a factor of 4. The reasons are 1) math or wording error (maybe you meant "the f-number should change by a factor of 4" ?); 2) the circle of confusion is conventionally larger for larger formats. Of course one would perhaps like to make sharper images from larger formats, but holding the c-o-c constant as one changes format is unrealistic. So if you are holding constant DOF = 2*coc*N*(d/f)^2 , then if f and coc increase by a factor 2, N also increases by a factor 2. So a 300/2.8 lens on 6x7 is roughly equivalent to a 150/1.4 lens on 35mm in terms of DOF.

A somewhat less formulaic way to see this is that (at fixed distance) rendering of out-of-focus areas depends only on the entrance aperture diameter. It's easier to show with diagrams, but: Think of the cone-shaped light beam coming from a point behind the plane of focus, crossing the plane of focus, and entering the lens aperture. This point will be imaged as a small circle, an image of the circle where the cone crosses the plane of sharp focus. So the size of that circle relative to the subject just depends on the entrance aperture. A 300/2.8 lens and a 150/1.4 lens have the same entrance aperture diameter in mm.

Of course, there is also the question of "what kind of picture do you want to make as the final product" where things like film grain and print magnification enter into the question, but that's a whole other can of worms.

 

[OAPOli]

The ratio f/N should be held constant, not change by a factor of 4. The reasons are 1) math or wording error (maybe you meant "the f-number should change by a factor of 4" ?); 2) the circle of confusion is conventionally larger for larger formats. Of course one would perhaps like to make sharper images from larger formats, but holding the c-o-c constant as one changes format is unrealistic. So if you are holding constant DOF = 2*coc*N*(d/f)^2 , then if f and coc increase by a factor 2, N also increases by a factor 2. So a 300/2.8 lens on 6x7 is roughly equivalent to a 150/1.4 lens on 35mm in terms of DOF.

Oops I meant f-number. I agree that the CoC should double.

Thus the depth of field will be even narrower than my estimation.

I think that one should compute the DOF directly using one's favorite CoC instead of drawing an equivalency using a hypothetical lens on some arbitrary image crop. 300/2.8 on 6x7 has similar DOF to 75/0.7 on m43 or 1200/11 on 8x10 but it doesn't tell us what the DOF actually is.

 

[flavio81]

A 300/2.8 lens and a 150/1.4 lens have the same entrance aperture diameter in mm.

Exactly

300/2.8 ---> 150/1.4 lens

But accounting for expectations of more resolution on the final print on medium format versus 135, then we should consider our DOF narrower.

Thus, that's why i said a 300/2.8 on a 6x7 camera would give a practical DOF similar to a 150/1.0 or 150/1.2 lens on full frame. Or even wider aperture (OAPOli would estimate it on f0.7)