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/
The Bronica 250/5.6 and 500/8 lenses for the ETR system are also incredibly cheap.
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.
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
I used to own the Pentax 67 M* 400mm f/4, so am familiar with that lens and its ability.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.
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.
The DOF of a 300/2.8 lens is the same on 135 or 6x7 or 4x5 but the FOV is different.
I've used a 112/1.4 aerial lens on 6x7 and focused it accurately. Maximum focus distance was <1m.
Cambridge Color DOF calculator says 300mm f/2.8 combination on 6x7 format would
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.
- 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)
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.
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.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.
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.
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.
Thus the depth of field will be even narrower than my estimation.
A 300/2.8 lens and a 150/1.4 lens have the same entrance aperture diameter in mm.
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