Cheap but good medium format lenses on digital?

[wuxiekeji]

I'm wondering if anyone has a suggestion for a cheap but good ~50mm, medium format (4x5) lens which is tack sharp on an APS-C sensor. Sharp when stopped down and sharp only at infinity is fine. I don't care about bokeh. I'm thinking about fixing the lens, throwing my camera body onto a motorized XY stage, build a dark housing for it and stitch together some gigapixel shots of landscapes. How is the Hasselblad 50/4 Distagon, and/or are there cheaper ones to be looking for?

(I ask here because I imagine there are people who are using these lenses as DIY tilt-shift lenses ...)

[iangreenhalgh1]

All medium format lenses by Nikon, Komura, Bronica, Mamiya, Zeiss, Schneider etc are pro level items and are all good. However, they are usually not so great on digital as 35mm lenses are.

I don't see the point in doing what you describe, all you need to make huge images is a tripod and a camera, no other equipment needed. Stitch using Photoshop, Gigapano or Microsoft ICE or whatever you prefer.

Here's a 168mp shot of a railway viaduct I did with my NEX-3 and Fujinon-TV 1.8/75:



This one is 149mp, I used my Konica Zoom-Hexanon UC 4/80-200 at the 80mm setting:

[wuxiekeji]

[iangreenhalgh1]

I don't find big shots that much of a problem to do manually, and I just used Photoshop's Warp function to correct distortion. I usually don't get much distortion, even with extreme stitches because I don't use wide angle lenses. I mostly use 50mm lenses of symmetrical design for stitching because they have very little distortion, and the less distortion the lens has, the less you get in your finished pano. Even a 28mm lens on APS-C can give you big distortion problems.

Also, you will get much better quality using a 35mm lens on APS-C as you're using just the sweet spot of the lens and overlapping the images anyways, so if you get it right, you should have the same sharpness and quality throughout the frame. With a MF lens where you are making use of the full image circle by moving the sensor around, you are going to get less quality, as even the best MF lenses aren't the same quality throughout their image circle.

If you want to automate the process, look at a motorised head like the Autopano one, one of those and something like a Planar 1.7/50 would be close to the perfect setup imho.

Here's a 4 x 12 stitch I did the other day with my Konica Zoom-Hexanon 4/70-150 at the 70mm setting. I corrected the distortion (which wasn't severe at all) with the Warp function in CS5:



There's been something bugging me about this shot, something looks slightly off to me and I just realised what it is - I corrected the distortion and perspective so that everything is ruler-straight and I have overdone it, the top of the buildings seem to loom at you - there should be a slight conversion of the verticals and by making them straight, it has made it look like the top of the building is bigger than the bottom, because the eye expects the verticals to converge slightly.

Thanks for the kind words.

[wuxiekeji]

[dan_]

"Cheap", "50mm MF lens" & " outresolve my APS-C sensor" are hardly going together in the same sentence.
A cheap & good lens is the Pentax-A 645 55mm f2.8. I have it, did some tests with it some time before and stooped down to f/5.6-f/11 it is sharp but not stellar. The Distagon is probably better. I've tested the Pentax-A 645 35mm too and and it behaves a little better.
The 35mm FA version is one of the best WA for medium format but isn't cheap.
Another MF lens I tested on APS-C is the Mamiya RB 65mm f/4.5. It may be your best choice as it proved to be very sharp, sharper then the Pentax lenses, and is cheap too. But is very heavy and bulky and adapting it to anything is really very difficult.

[iangreenhalgh1]

[kiruajon]

[iangreenhalgh1]

I hope this helps. I just stuck my camera on a tripod outside my back door and made a pano, it's 6x9 shots, should be 54 total but I missed a couple and had 52.

I used my Hexanon 1.4/50 at f11, seven then, dof was not sufficient, with a scene like this where you want everything from foreground to background in focus. You can stop down more, but will lose a little sharpness, or use focus stacking, which I have yet to try as it multiplies the number of shots and amount of data to process. Even with 8gigs in my PC, I had to put this thing together in 3 pieces.


#1

#2

#3


#4 After putting the three pieces together, I then joined them, all using Photoshop CS5. The resultant image is 22200x9884, which is a little over 209mp.



#5 As you can see, there is almost no distortion, but the camera was slightly off level by 4 degrees, so I had to rotate the picture.



#6 Crop it to remove the excess:



#7 Now a little warping to fix some minor issues.



#8 A final crop to remove the dull left hand side and a little excess sky, and a little tweaking of brightness and contrast and the end result is this image, 16827 x 6715, which is 108mp.



So, to get a gigapxel image, you're going to have to use a long lens, say 200mm, and you're going to have to resort to focus stacking to get everything in focus with a lens that long. This is going to mean you will need one hell of a lot of horsepower in your PC, I'd say 32 or 64 gigs of RAM and a dual socket motherboard with a pair of 8 core processors. I have a 4 core processor with 8 gigs of RAM and it is only feasible to create images in the few hundreds of mp, gigapixel work would be out of the question.

[Attila]

Thank you Ian , very useful!

[kiruajon]

Thank you !

[iangreenhalgh1]

You're very welcome, mon amis!

[wuxiekeji]

[bernhardas]

edited

[iangreenhalgh1]

Thanks for the kind words guys, much appreciated.