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Author Topic: View cameras (2:3 / 6:9) and DBack -- but NO ground glass or shift/slider  (Read 1537 times)

Codger

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Hello, all:
     Have read reviews the past two months that seem to be pointing me to putting a digital back on a 679 or Techno.  When I look closer it appears one has to work with an accessory that holds the back out of the way for composition and focusing, then requires a shift to position the back for capture.  What technical advancement will there have to be before the back is attached and used directly for comp and focus, as with the PhaseOne or 'Blad bodies.  Can they do it because of their reflex viewers (that invert and reverse the image)? What if one was content with working with the upsidedown and backwards view on the DB screen?  Will this happen?  Thanks, all.
     Codger
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billthecat

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I bought a $200 4x5 to Mamiya M645 adapter from China on Ebay. With my Mamiya AFD I can focus and get confirmation, as well as viewing the image. Then I can take a 3 shot pano of the image as it slides. It fit easily on my 4x5 Speed Graphic.

Because the digital sensor is way back from the film plane my wide lenses don't focus more than the front of the camera, and I liked my wide lenses the best. I'll play with it tonight some more. My Darlot 8x10 lens works fine but the crop is so much that it is uninteresting.

Bill
« Last Edit: May 12, 2011, 12:21:00 am by billthecat »
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Anders_HK

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Digital requires more precise tolerances than film. A reply I received from Schneider;

"Basically the tolerance for digital imaging should be less than 0,02mm for the infinity adjustment otherwise you will get serious problems with the sharpness especially with wide angle lenses.

For focusing on closer distances the sharpness plane will move more or less, which is also not good.

You will have a very hard job when trying to get sharp images with a combination of a view camera and a sliding back, where fortune decides about image quality.

Best results will be achieved with Alpa or Cambo cameras which use a viewer and a perfect aligned lens helical mount combination."


In comparison to above, film flatness should typically be around 0.2mm tolerance, a difference of 10x.

Thus if we speak of adjustment to such precise tolerances for optimum sharpness on high resolution digital back it seems what is required:

1. micro adjustment drives of lens movements and focus
2. means to view or with to see this preciseness of focus, whether teathered, or by a high accuracy focus mask (maybe ok on new IQ backs, maybe?), or a precision groundglass with groundglass perfectly shimmed to say within 0.01mm of sensor plane and a suffice magnifier

If we speak of using a medium format dslr on adapter to viewcamera, such too (dslr and adapter) have tolerances same as a groundglass, but if we also add stitching so does sliding adapter and its sliding plane, and we have more weight hanging on rear standard...

It also depends on the resolution of digital back used since higher resolution will magnify errors with blown up print size. For sliding adapter I have one for Mamiya 645 system backs for sale. It is a custom fabrication per my own design and precision made with a LARGE high quality Maxwell screen. The adapter works fine for lenses 72mm focal and longer on my 28MP Leaf. The sliding adapter is made to higher quality than cheap Chinese ones sold on Ebay. Material is duralumin, better than aluminum... Price is already what seems a steal...

http://www.luminous-landscape.com/forum/index.php?topic=51965.msg436529#msg436529

Regards
Anders
« Last Edit: May 12, 2011, 01:26:06 am by Anders_HK »
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Graham Mitchell

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Live View focusing replaces the need for any focusing screen, although it may not be suitable for all subjects. For landscapes, architecture, table top, etc, this is the way to go.
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Codger

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So, Graham, is what I need to watch for (wait for?) a good back (such as IQ160, etc.) that has or introduces Live View?  I've read about some manufacturers providing corrective mounting and alignment of specific body/back combinations.  Leaving out the slider/adaptor would seem to tighten up the geometry and make a more compact package.  Codger
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cng

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There are two types of Live View – tethered and untethered.  No-one really knows what untethered Live View on the new IQ backs will look like until the firmware update in June.

Some hold the opinion that using a GG and/or sliding back will not really guarantee focus because the GG will sit on a very slightly different plane compared to the sensor.  So you may have to compose and focus with the GG, shoot, check focus, recompose and/or refocus if necessary, then reshoot.
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