Analysis of the 8x10 / IQ180 comparison

[rdenney]

Just what is the problem with writing more than a paragraph on this subject?

There have been many, many digital-vs.-film comparisons of the "one-paragraph" variety. I've done some myself. I find it ironic that those who complain of the detail required in a really careful test are often (not always) the same ones who react negatively to any comparison of the one-paragraph variety.

Quite simply, one paragraph is not enough to either slay or spare whatever sacred cow most experienced readers happen to worship. If it were, we'd have no sacred cows left, yet the worshiping seems to continue.

Rick "not sure, however, that it is necessary to choose apertures that deliver the same depth of field, unless out-of-focus details are the basis for the comparison" Denney

[timparkin]

There have been many, many digital-vs.-film comparisons of the "one-paragraph" variety. I've done some myself. I find it ironic that those who complain of the detail required in a really careful test are often (not always) the same ones who react negatively to any comparison of the one-paragraph variety.

Quite simply, one paragraph is not enough to either slay or spare whatever sacred cow most experienced readers happen to worship. If it were, we'd have no sacred cows left, yet the worshiping seems to continue.

Rick "not sure, however, that it is necessary to choose apertures that deliver the same depth of field, unless out-of-focus details are the basis for the comparison" Denney

I think he was asking "what is the problem of writing *more than one paragraph* on the subject".

And as for the 'not necessary to choose the same aperture', why would you want to choose different apertures when recording the same photograph? If you are comparing equivalents, isn't the aperture part of that equivalent? Unless you are doing copy work then the resolution of defocussed areas is a major part of the character of a picture?

Tim

[rdenney]

And as for the 'not necessary to choose the same aperture', why would you want to choose different apertures when recording the same photograph? If you are comparing equivalents, isn't the aperture part of that equivalent? Unless you are doing copy work then the resolution of defocussed areas is a major part of the character of a picture?

Most of us work in multiple formats, and just work around (or with) the difference in depth of field. Trying to force 8x10 to have the same depth of field as 645 might not be that relevant in application, because photographers will use other means to get the sharpness they need (such as tilt or swing), or compose differently to work with those differences. If the equivalency falls within the apertures that people normally use, then fine. (And it might--my quick check of DOFMaster indicated that f/11 and f/45 would provide similar depth of field between 645 and 8x10.) I would evaluate fine detail and resolution in the focus plane and do so accurately--that was a major issue with the LuLa test, as you discovered.

Also, the added depth of field (for smaller prints) provided by smaller formats is one of the advantages of using a smaller format. I'm not sure we need to provide that, though.

In terms of the character of defocussed images, it seems to me that lens design will play a major role--maybe enough to overwhelm other differences.

Rick "who would not use an extraordinary aperture setting just to match DOF with a different format" Denney

[timparkin]

Most of us work in multiple formats, and just work around (or with) the difference in depth of field. Trying to force 8x10 to have the same depth of field as 645 might not be that relevant in application, because photographers will use other means to get the sharpness they need (such as tilt or swing), or compose differently to work with those differences. If the equivalency falls within the apertures that people normally use, then fine. (And it might--my quick check of DOFMaster indicated that f/11 and f/45 would provide similar depth of field between 645 and 8x10.) I would evaluate fine detail and resolution in the focus plane and do so accurately--that was a major issue with the LuLa test, as you discovered.

Well you may work like that but a lot of people work differently. The f/11 and f/45 are both well into diffraction and hence you are limiting the capabilities of both systems. Many people shoot medium format 645 at f/ 11/16 which is the equivalent of f/64, a commonly used aperture for 8x10 users from my understanding.

The IQ180 has a critical aperture of f/5.6 for which the equivalent is f/22 2/3

Typical working aperture for a 645 may be f/8 which would be the equivalent of 32 1/3 which seems typical for both systems (this works out as f/22 1/3 - again not uncommon for 4x5)

Surprisingly, the most common apertures for 645 are similar to 4x5 and 8x10 (when made equivalent). The factor from IQ180 to 10x8 is 4.85. (2.42 for 4x5).

The test is about people who may wish to use IQ180 instead of 8x10 and hence the equivalents are even more important than usual (whether they end up using an ALPA or a Linhof Techno).

Also, the added depth of field (for smaller prints) provided by smaller formats is one of the advantages of using a smaller format. I'm not sure we need to provide that, though.

This is a complete fallacy - larger formats have just as much depth of field as smaller formats, diffraction merely reduces the available resolution from larger formats but they never get worse than the equivalent smaller format.

In terms of the character of defocussed images, it seems to me that lens design will play a major role--maybe enough to overwhelm other differences.

Absolutely - how was this bit relevant?

Rick "who would not use an extraordinary aperture setting just to match DOF with a different format" Denney[/QUOTE]

If you do the math, extraordinary apertures are similar for 645 and 10x8. Once you get to f/22 on medium format (which is losing a lot of resolution) the equivalent is f/64 2/3

[Robert Hughes]

Well, we're glad you like LF and the IQ180 Tim, but going up against rdenney and other long time photographers is not helping your case.

[timparkin]

Well, we're glad you like LF and the IQ180 Tim, but going up against rdenney and other long time photographers is not helping your case.

Forgive me if it sounded like I was going 'up against' anybody. I was merely trying to get to the bottom of

Rick "not sure, however, that it is necessary to choose apertures that deliver the same depth of field, unless out-of-focus details are the basis for the comparison" Denney

i.e. what is the alternative and why is it a problem to choose equivalent apertures.

How will people respond if I choose different equivalent apertures is also an issue. And which different apertures to use.

[Brian C. Miller]

Well, we're glad you like LF and the IQ180 Tim, but going up against rdenney and other long time photographers is not helping your case.

Tim is doing the testing. If you think you can do a better test, find someone with an 80Mp back and go for it! Offer them coffee and lunch and see what happens. That goes for the rest of you. No armchair analysis, go out and do it! There's someone with an 8x10 in every state, maybe more than one. Finding somebody with an 80Mp back may be harder.

At worst, what could happen? "My Schneidestock Unobtainagon got crushed when my film holder slipped!" or "I backed over my new 80Mp camera with my new Porsche SUV!" But best case, you'll wind up with some film to put under a microscope, and something to muck with in Photoshop.

[E. von Hoegh]

Using the so-called equivalent aperture of f64 (on 8x10) introduces much more diffraction, limiting the available resolution.

Are you guys talking about depth of field, or depth of focus?


I remember reading an artcle in Shutterbug, back in the late 80s. "Anything 4x5 can do, 35mm can do, easier and better" by Otha C. Spencer. Arrant nonsense, of course, but it reminds me of the IQ180 and 8x10 comparison, in that the author sought to prove something by comparing things that really are not comparable.

[goamules]

These scientific or quasi-scientific film vs digital tests are interesting to me. And since the technology of at least one media is evolving, how could anyone suggest further testing is beating a dead horse. To me it's like those people want to put their fingers in their ears and start singing "la..la..la...I can't hear you...la...la".

These tests are important because they attempt to answer the *age-old question, "which is better." I went to a Fall art show last weekend. There were several booths of over saturated, heavy photoshopped giant color landscape prints. All the "artists" shot digital. Buyers were lining up. I had a film camera with me, and the age old question came up several times. What do you answer? Inquiring minds want to know.


*an age in today's tech world is approximately 1 year.

[John NYC]

These tests are important because they attempt to answer the *age-old question, "which is better." I went to a Fall art show last weekend. There were several booths of over saturated, heavy photoshopped giant color landscape prints. All the "artists" shot digital. Buyers were lining up. I had a film camera with me, and the age old question came up several times. What do you answer? Inquiring minds want to know.


*an age in today's tech world is approximately 1 year.

You can photoshop the wazoo out of scanned film as well. The answer to the particular age old question you are asking here is "there is no accounting for [Ed.: lack of] taste."