Thinking about upgrading both ends of my Cambo Actus G. Suggestions welcome.

[stevev]

I am contemplating an affordable digital back of some kind on my Actus G to replace my Sigma fpL. Certainly less than $10K USD, preferably less than 5. I realise that It may not exist at that price.

The goal is to make shifted panoramas with a slightly wider angle of view by having a slightly wider sensor and the freedom to choose lenses slightly wider than my Mamiya RZ67 50mm ULD or Rodenstock 55mm APO Sironar digital, that are both compact and have large image circles.

It may be that the most affordable option is to use the 44mm wide sensor on a GFX body and use the existing lenses, but the 50 is heavy and the 55 has a strong peripheral cyan colour cast.

Any suggestion?

 

[Alkibiades]

digaron-S HR 4-60 mm.
A lens that can be used with GFX on Actus, have no color cast issues, is some class above the 55 mm and mamiya 50 mm in sharpness and resolution. Simply the best lens in this range ever made and much cheaper than the bigger digaron-W 50 mm ( that cannot be used with GFX)

 

[rdeloe]

Some questions...

• What is the aspect ratio of these shifted panoramas that you want to make?
• Do the lenses you are looking for need to be off-the-shelf, or are you willing to modify lenses to get where you need to go?
• If you found a lens that met your criteria, would you stick with your Sigma, or are you looking for a reason to switch to GFX, or some other camera body?

 

[stevev]

Alkibiades - thanks.

Hi Rob,
Answers are
1) 3:1
2) willing to modify if I don't need specialised skills or tools
3) a wider sensor will get me a wider angle of view with a lens with a suitably wide image circle. I am stuck at around 24mm equivalent (don't have my spreadsheet handy) with the Sigma and 50mm RZ, and would like to be able to get closer to 20 or 21mm equivalent after stitching. So wider virtual sensor and small, wider lens are needed.

Cheers,
Steve.

 

[4x5Australian]

Hi Steve. You asked about a digital back under USD 5,000.

Phase One P45+ digital backs were introduced in 2007 and can be found now for less than USD 5,000.

The Kodak KAF-39000 CCD sensor in the P45+ is 39Mpx and 48.9 x 36.7mm in size. Pixels are 6.8 micron.

Negatives:
There is no live view, and the resolution of the rear LCD is low by modern standards.
That means you focus the lens by some other means, such as a distance scale or on a ground-glass.
Distance scales work well, especially for infinity at f/11.

Positives:
Freedom from the restrictions on short focal length lenses.
It's a small, almost indestructible brick (going by reports of them surviving multiple falls onto concrete).
Nice clean images.
Price!

With the P45+ I recommend the SK 35XL and SK 47XL lenses, which are small and lightweight.

Rod

 

[drevil]

P45+ backs can go well below 2000usd these days
i recently acquired an IQ180 for less than 3000euros

live view is not comfortably usable on CCD backs, the next affordable back with live view would be one with the 50MP sony sensor, but that sensor has a very heavy crop, thus wide angles will not be really wide anymore

 

[asnapper]

The Rodenstock 55mm APO Sironar digital can't be used with the Actus G & a GFX camera, I've tried, but the SK 47mm Apo Digitar does, but you are limited to about 9mm of shift due to the lens protruding inside the the Actus GFX mount. A digital back will give you more lens options, but the user experience may not be as pleasant as using either a Fuji GFX or Hasselblad XD series camera in combination with the Actus G. If you are set on getting a digital back, how about a s/h Hasselblad 50 or 100MP digital back

 

[rdeloe]

Alkibiades - thanks.

Hi Rob,
Answers are
1) 3:1
2) willing to modify if I don't need specialised skills or tools
3) a wider sensor will get me a wider angle of view with a lens with a suitably wide image circle. I am stuck at around 24mm equivalent (don't have my spreadsheet handy) with the Sigma and 50mm RZ, and would like to be able to get closer to 20 or 21mm equivalent after stitching. So wider virtual sensor and small, wider lens are needed.

Cheers,
Steve.

To get 3:1 with a 3:2 format full frame camera, you need 18mm of shift on the long axis. That's a 76mm image circle and quite do-able with several lenses. To get 3:1 on GFX you need a 27.5mm shift on the long axis and a 104.1mm image circle. You have two problem now. First, a lens with good image quality in a huge image circle like that in the focal length you want is going to be hard to find. Second, with a shift of that size, you get hard vignetting on the GFX. That's actually a solvable problem if you shoot three frames because your stitching software can handle it -- but you'll always need three frames.

Were I in your shoes, I think I'd stay with the Sigma for this job.

In 60mm, the Digaron-S 60/4 that Alkibiades recommended has a 70mm image circle according to Rodenstock. His testing on another thread suggests you can go beyond that. I can neither confirm nor deny. If you want to try, I've seen these for reasonably money in electronic shutters and it is quite straightforward to re-house them in a B-0 Schneider-Kreuznach housing from a Componon-S 100mm, 135mm or 150mm enlarger lens. You may have to fine tune the shim spacing, which is not hard. And you will have to adjust the aperture, which is also not hard.

If you want wider, the Pentax 67 55mm f/4 third generation lens is a big one, but would be an easy, off the shelf solution. It has a close focusing system so you'd need to set it to its flange distance on your Actus and then focus by lens. It's a retrofocus design so you will get the moustache distortion that is typical of retro wides, but I doubt it will bother you in typical landscape/city scape scenes.

I've previously recommended the Mamiya G 50mm f/4 L. A properly calibrated one is excellent: sharp, and effectively free of distortion and other aberrations. The catch is it has to be hacked. Step 1 is send it to Bill Rogers in Nevada to deal with the shutter and other internal bits that have to go. Step 2 is send it to SK Grimes in Rhode Island to mount on an Actus plate (if you're not comfortable doing that work yourself). Potential Step 3 is fine tune the cell spacing. This third step is required for GFX, but if you stick with your Sigma it may not be necessary. The issue is the factory cell spacing doesn't work with the thick cover glass of GFX lenses. It's easy to do yourself once.

This post has an image with the Mamiya that used 13.5mm of rise on GFX: https://www.getdpi.com/forum/index.php?threads/technical-camera-images.29667/post-918369

One last thought: I don't do a lot of panos like this, but most of the time when I tried it, I ended up using a cropped single GFX 100S frame made with a wider lens, rather than the flat stitched higher resolution image made with a longer lens that had the same field of view after stitching. An 11, 648 pix wide single frame image turned out to be plenty, and usually was stronger because pushing into the outer part of the image circle of any lens has a price -- usually a combination of field curvature and contrast reduction. A compromise position if you are after an enormous number of pixels is to do something like a 2:1 flat stitch on GFX and then cropping that to get to 3:1. You'd only need 11mm of shift on GFX to get to 2:1. That gives you 17,500 pixels on the long edge. Even at 300 ppi that's a 58" print. Lots of lenses can easily handle 11mm of shift on GFX.

 

[stevev]

Thanks everyone for your suggestions.

A quick look at eBay suggests that the P45+ and SK47XL combination is in the ballpark budget-wise. And it would certainly be wider after stitching than my current setup. But the 39MP would mean a drop in resolution in the final image, so in that respect I would be worse off. With the 60MP Sigma I can get a 3:1 pano 21,000 pixels wide (36mm plus 20mm left and right plus a tiny bit of rise or fall to crop to 3:1) but unfortunately can't get wider than about 24mm equivalent field of view with a 50mm lens on the front.

Rob, yes, the 60mm Digaron lens Alkibiades mentioned has an image circle of 70mm, and I believe his testing did show that 15mm of shift was the practical limit on a 44x33 sensor. But 60mm on a GFX sensor when only shifted 15mm won’t get me any wider, given that I currently can shift 20mm at 50mm on the fpL. I had the last gen Pentax 67 55mm but the Mamiya RZ67 50mm ULD is wider and at least as good. And I am not sure that the Mamiya 50mm G would be any better than the excellent but large and heavy Mamiya RZ67 50mm ULD that I use.

A GFX100 of some kind on the back of the Actus would get me 44mm plus 20mm plus 20mm (an 84mm wide virtual sensor) and would increase resolution to about 23,000 pixels wide, by my rough calculations. I could do that in 3 shots and crop to 28mm high to get 3:1, versus the six I need now to crop to get 3:1 at 76mm wide by 25.3mm high. It would be a useful but incremental improvement. And then as was mentioned, the 55 Rodie is no longer useable, with no other small, wider lenses available. So I would still need to use the ULD…

I suppose my quest is to find the best, affordable, digital setup capable of getting 6x17 film resolution AND getting out to about 21mm equivalent horizontal FOV after stitching. Interestingly, it seems that the shifted GFX pano area I mention above is almost exactly one quarter of the useable area of 6x17 film, yet yields slightly better resolution than a 6x17 scan at 3200 dpi. A GFX sensor gets me to about 22 degrees horizontal equivalent after stitching, a two degree improvement on the Sigma.

Bottom line seems to be that there is probably an 80MP or so digital back in my distant future, but bang for buck, for my very specialised use case, the setup I have now, does well, and will have to do.

Thanks for your ideas.
Steve.

 

[anwarp]

A quick look at eBay suggests that the P45+ and SK47XL combination is in the ballpark budget-wise. And it would certainly be wider after stitching than my current setup. But the 39MP would mean a drop in resolution in the final image, so in that respect I would be worse off.

mpb.com in the uk has an IQ260 listed under 3000GBP. This is an excellent 60 MP large sensor back that works well with SK lenses. I have heard that the IQ180/280 have colour cast issues with the shorter SK lenses.

 

[stevev]

Thanks anwarp. Had a look and could not see it there…? Sounds perfect!

 

[4x5Australian]

Thanks anwarp. Had a look and could not see it there…? Sounds perfect!

Here 'tis:

https://www.mpb.com/en-uk/product/phase-one-iq2-60-digital-back

 

[stevev]

Thanks Rod.