Using non-digital lenses with a digital back

[NoBob]

Hi,

Anyone use non-digital LF lenses with a digital back? How well do they work?

[darr]

I have used my Cooke PS945 with a Phase One P45 back and think it does fine.



Camera: Arca Swiss + P45
Focal Length: Cooke 229 mm
Exposure: f. 5.6 @ 1/4 sec
ASA: 50
Date: 01-15-2010

[Peter Mounier]

They work very well together. Here are a few shots that I took with a Betterlight Super 6k-HS, then put up with Zoomify software...

http://www.MorroBayGiclee.com/

Peter

[NoBob]

Thanks. How did you work around the film's uneven/sensor's flat and movements/image circle issues?

[Peter Mounier]

I had to read another post you were commenting in (about Digitar lenses) to understand what you meant by "film's uneven/sensor's flat" question. If you're asking about critical focusing at the different depths of the color layers of film as opposed to the flat sensor, then digital lenses are better, but those differences are not likely to be seen with a human eye. At least I don't see it, but if it's possible, I'm sure I'll be corrected.
Regarding the image circle/movements part to your question, I think there's more relevance to medium format sensors than to Bettterlight sensors since the Betterlight sensors cover almost the same area as 4x5 film (3x4 approx). It's slightly smaller but movements aren't restricted when using the Betterlight.

Peter

[Sevo]

YMMV - there are no "digital lenses", but lenses designed or marketed for digital, and what each manufacturer considers fit or unfit for digital varies with the purpose.

For one, digital is smaller, digital medium format is mostly smaller than 6x4.5cm (and many digital view cameras use medium format backs), and even "digital large format" scan backs rarely exceed quarter plate (3x4") useful area. Accordingly, many "digital LF" lenses have no direct precursor you could alternatively use, as even the shortest traditional LF lenses are longer (or way too wide).

Apart from that, some lens designs will not do on digital area sensors. The very flat angle of incidence from large format ultra wides is incompatible with common sensor designs which need a fairly perpendicular incidence, so that "digital" wides, besides being shorter than the lower limit of 4x5" lenses, must employ a retrofocus design. The filter plates in front of the sensor have to be considered too - some lenses need a recalculation, and a plain glass rear filter of similar strength when using them with film. And some lenses have issues with reflections between the (highly reflective) sensor and rear element, and need a redesign with different rear element curvature or more effective rear element coatings.

But with scan backs and normal to long lenses, you'll only be suffering from resolution loss if you use a LF lens designed for a bigger format and lower resolution than a relatively small digital back - nothing I've ever noticed with my somewhat outdated 12Mpx back, but at higher resolution you may hit the lens limits before the sensor limits.

Sevo