Okay so, like I mentioned in the first post [link] I am playing with the idea and practicality of adapting old manual medium format Pentax67 and Pentax645 lenses to my Sony A7RII.
First up I should say that I started out by using the Fotodiox EOS to E mount adaptor, but turns out that gives very hard vingetting(strangely the more it was stopped down the worse it got… the opposite of the norm) So luckily I also have the Commlite EF to E mount adaptor which has no issues at all, and is a good fit the Pentax67 to EF adaptor.(it has electrical contacts for auto focal lenses etc, but those will obviously not be used for this test) Eureka!
The Pentax67 55mm f4 Asahi SMC lens.
When I first started this endeavor I was of the understanding that the field of view for P67 mount lenses on a 35m sensor would “double the focal length” (Field of view (FOV) would be half of that of the Pentax 67 system as the P67 is approx. 2 times bigger than the 35mm sensor, AND that I would have to double the aperture for the equivalent amount of depth of field (DOF) gathered light would be the same as the physical specs of the lens have not changed.)
In essence the Pentax67 55mm f4 lens will act as 110mm f8 lens, but gather light as an f4 lens once on a full frame body.
Wikipedia for reference: https://en.wikipedia.org/wiki/35_mm_equivalent_focal_length
Now with these great lenses and adaptors you can of course get some great bokeh even if it acts as a 110mm f8 Full frame equivalent lens as long as you get close. And this particular setup will focus as close as 35cm (see the pictures below) some pretty awesome bokeh and seperation.
Okay, so now for the sharpness test. -spoiler alert!- Its damn sharp! Σ(￣□￣)
Here is what I am doing to try and get comparable results. I.e consistent setup
- Level and 90degrees shooting for even length to focus plane and the setup.
- Same framing for all lenses. I.e longer focal length will be shot from further away to achieve same framing. (see images below)
- Lighting is done by softbox and flash to eliminate any motion-blur.
- ISO50 for low noise, 1/200sec shutter and exposure adjusted through flash.
- Shot tethered into CaptureOne Pro 9, with only White balance, CA and Crop adjustment - No additional sharpness added. exported to 100% quality Jpeg in sRGB at 2048px wide.
Above shots are f4, f5.6, f8, f11
Below is a 100% crop for pixel peeping, please open the image in a new window or download to see in full size.
Sorry for the somewhat random real-life examples... more and better examples will come eventually.
I think it is fair to say that this old Pentax67 55mm f4 MF lens have an amazing amount of resolution and the creamy out of focus area and the great construction is well worth the 18.200¥ at MapCamera in Shinjuku.
And although it is heavy and awkward on the SonyA7RII, it is a great lens with much to offer.
Next step is getting a proper lens hood, as it is prone to flare when shooting outside in the sun.
If you enjoyed this article stay tuned to this blog as 4 more MF lenses are reviewed over the next few months. Next up for testing is the Pentax67 105mm f2.4 SMC and it will have much better real-life images to go with the test shots as I have been shooting a lot more with this lovely beast. ♥