Image quality from digital vs analog lens both shot on film

[Drew Wiley]

I hope to run some tests with some of my very sharpest 4x5 lenses, a Horseman 6x9
back, and R25 film in a week or two, but want everything precisely optimized first (I'll check the film plane with precision tools). My own question would be whether a dedicated digital lens in anything but a wide-angle perspective relative to this format would have any distinct advantage over the best 4x5 lenses, given the facts of life with film plane accuracy and the need to stop lenses down relative to typical subject-matter depth of field. My guess is that once you start getting in focal lengths around or below normal (say 100mm or less) the digital lenses are going to start showing their superiority in a practical rather than theoretical sense.

[J Maxwell]

I hope you'll post the results of your tests, Drew, on the forum. I'd be very interested in hearing detailed coverage of your findings! Those are my questions, too. The specs on the Schneider / Rodenstock digital lenses sound very promising, but, the proof is always in the print.

[rdenney]

The digital designs are needed to provide wide-angle fields of view with the smaller digital formats that thus require shorter lenses. Those short focal lengths are difficult to accommodate with view cameras of any type using conventional approximately symmetrical designs. Also, they try to overcome the cosine law to provide more even illumination of the frame and to allow the light to strike the sensor more directly. Both of these require much more distance between the glass and the image surface. The digital lenses have a retrofocus design to address these issues.

As I understand it, they are also optimized to provide high MTF at spatial frequencies relevant to digital sensors, but low right at the spatial frequency of the sensor so as to minimize moire. That is received knowledge and not personal experience, so it is subject to be refuted by those who know more.

I've generally found the symmetrical designs used for large format to be sharper than the same focal length lens designed for SLRs. An example is a comparison between the 47mm Super Angulon (old--pre-XL f/5.6) and the 45mm SMC-Pentax 67 (much newer, but heavily retrofocus for the big SLR and not new enough to take advantage of the latest special glasses). I found the Super Angulon to be sharper at the film plane, but the Pentax is still quite excellent. I suspect the 43mm Mamiya 7 lens benefits from not needing the same degree of retrofocus. That the digital lenses overcome the inherent limitations of the retrofocus design seems to me remarkable.

Rick "suspecting those new Digitars, etc., take advantage of better computer optimization and a range of previously unused special glasses" Denney

[Asher Kelman]

Not done the exact comparison but I've had a few 1dskm3 files taken on a 16-35mm and some 5x4 ektar enlarged to 30"x20", taken on a 150mm, and then drum scanned.
Film easily wins.
The gradation between the tones is much better and the film has a softness I much prefer.

Ed,

I use Canons as my main digital workhorses. First the 16-35 mm Canon lens is hardly stellar. As a standard the 14-24 Nikon is accepted to be the lens to refer to for resolution and contrast reference. But then one should adapt the Ektar to that format. 4x5 has 20 square inches of real estate compared to the 1DsIII. so at the outset there's ~ 15 times resolution to start with if they were equal!

Asher

[Sirius Glass]

The digital designs are needed to provide wide-angle fields of view with the smaller digital formats that thus require shorter lenses. Those short focal lengths are difficult to accommodate with view cameras of any type using conventional approximately symmetrical designs. Also, they try to overcome the cosine law to provide more even illumination of the frame and to allow the light to strike the sensor more directly. Both of these require much more distance between the glass and the image surface. The digital lenses have a retrofocus design to address these issues.

As I understand it, they are also optimized to provide high MTF at spatial frequencies relevant to digital sensors, but low right at the spatial frequency of the sensor so as to minimize moire. That is received knowledge and not personal experience, so it is subject to be refuted by those who know more.

I've generally found the symmetrical designs used for large format to be sharper than the same focal length lens designed for SLRs. An example is a comparison between the 47mm Super Angulon (old--pre-XL f/5.6) and the 45mm SMC-Pentax 67 (much newer, but heavily retrofocus for the big SLR and not new enough to take advantage of the latest special glasses). I found the Super Angulon to be sharper at the film plane, but the Pentax is still quite excellent. I suspect the 43mm Mamiya 7 lens benefits from not needing the same degree of retrofocus. That the digital lenses overcome the inherent limitations of the retrofocus design seems to me remarkable.

Rick "suspecting those new Digitars, etc., take advantage of better computer optimization and a range of previously unused special glasses" Denney

Thanks!

[edtog]

Ed,

I use Canons as my main digital workhorses. First the 16-35 mm Canon lens is hardly stellar. As a standard the 14-24 Nikon is accepted to be the lens to refer to for resolution and contrast reference. But then one should adapt the Ektar to that format. 4x5 has 20 square inches of real estate compared to the 1DsIII. so at the outset there's ~ 15 times resolution to start with if they were equal!

Asher

Just hope you never had the unfortunate experience of using the mk1 version

[Drew Wiley]

Rick - I've found that the biggest problem if lenses are used optimally is simply the film
itself. You can only capture so much. For example, my sharpest Pentax 6x7 lenses require an extremely fine film like R25 to illustrate their full potential, which allows me
a surprisingly detailed 16x20 silver print but obviously no movements. So I'm doing things like pitting the 165/2.8 Pentax again a 180 Fuji A on a roll-film back to make a
comparison at comparable apertures. With the Pentax I find that I often have to use
smaller than ideal apertures just to cope with the depth of field issue; but this camera is known to hold film flatter than many roll film backs. The shortest focal length lens I
own for 4x5 which seems really sharp enough for MF work is my Fuji 125/5.6 W. My main personal interest is in very long focal lengths relative to format. Once you get way way out there, the nature of the intervening atmosphere is a bigger issue than
nitpicking MTF. It's those shorter focal lengths where the digital lens category would
seem enticing; but I notice there are different series based upon the intended size of
the sensor, and only certain lenses are suitable for MF film sizes. Precise focus becomes a big deal. I printed a 20x24 C-print the other nite from 6x7 Ektar just to
see what would hold. Of course I double masked it for contrast and saturation, and I
basically hate to try this degree of enlargement from something that small; but it still came out crisper than what I'd expect from a scan and digital prints. Trying to kill a
number of birds with a single stone, and believe me, that Ektar is some impressive film
both in terms of color response and sharpness.

[sanking]

As to the wider debate over scale of reproduction, there is simply no way any kind of MF capture, digital or film, can
compete with the detail of a proper 4x5 shot (let alone 8X10), especially if it is optically printed.

Drew,

You are just dead wrong about this. The Mamiya 7II, used on a tripod with the lens at optimum aperture, will easily match detail of 4X5 in B&W photography. And if you use a finer grain film with MF than with 4X5 (say Fuji Across with the Mamiya 7II and HP5+ or TRI-X with the 4X5), the MF negative will also equal or beat 4X5 in tonal quality.

And I am mean absolute image quality, not print quality at a given print size.

Sandy King

[Steve Barber]

Just hope you never had the unfortunate experience of using the mk1 version

What is wrong with the MkI version?

[Drew Wiley]

I have a lot of respect for you Sandy, but you're giving folks a strange impression if you expect ANY kind of MF system to compete with a view camera for detail, with any
kind of lens. No matter how good the lenses are, size matters. And once someone starts printing color, the difference is ovewhelming. Even in a 16X20 silver print I can
easily spot the difference between what was MF and what was 4X5, not to mention
8X10, which is basically Godzilla vs Bambi. Tonality and hue saturation, plus the fact
that higher ASA's can be used in bigger film sizes, vastly less spotting issues, movements, compatability with masking techniques due to dimensionally stable films -
all these thing cumulative add up. MTF detail is just one factor in many that determines overall print detail and quality. What works efficiently for you might or might no work as well for someone else. Sure, I'd like to own a M7 myself for certain
uses, but no way it will ever replace the role of sheet film. Even the limited lens
selection would be a deal breaker.