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Author Topic: Post processing IQ180 files for resolution/camera test  (Read 10910 times)
timparkin
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« Reply #20 on: October 27, 2011, 07:49:20 AM »
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I'm in London...we have 3 UK dealers plus a regional sales manager who takes care of Phase One, Leaf and Mamiya

BR Yair

I which case I could be very interested :-) If you want to email me, my address is on timparkin.co.uk

Tim
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BartvanderWolf
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« Reply #21 on: October 27, 2011, 09:42:38 AM »
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Hi folks, I've been working with a few photographers and engineers to organise a big camera test (as part of a retest for the IQ180/8x10 article featured recently). We're comparing the results from an IQ180 on with Alpa WA/Digaron 40, Cambo/Digaron 35 & Phase 645/Digital 45mm shot in a studio (without flash but with daylight lighting booth). We had photographers who use both large format and MFDB's with us including a Phase One distributor to make sure the photographs were taken correctly. For the 8x10 and 4x5 shots I am happy with post processing these having scanned them on a Howtek 4500 (and checked the scans on a microscope and against a colleagues ICG 800dpi scanner) but I am interested in opinions on the optimal post processing for these files.

Hi Tim,

I'm already looking forward to the results, as it seems to be a well managed and executed process done by openminded people who know what they're doing.

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When I'm comparing the 80mp files against the 8x10 4000dpi scans (40,000 x 32,000) should I up rez them and how and also in terms of sharpening etc, do I let Capture One handle everything on auto (probably not) or do I just get a raw capture and use Photokit? etc, etc. We will be printing them as well but they will also obviously be displayed on screen for people to assess as most people won't be able to get to the 'show' we're hoping to give.

There are IMHO 2 aspects to a good film scan. The first is to extract all resolution, and second to minimize the distraction from graininess, and there is a trade-off between those parameters. In practice it means having to scan the film with something like 6000+ PPI by a competent operator who can balance the scanning aperture size with the grain/dye cloud structure. Smaller scans will perhaps not extract all detail, and increase the grain-aliasing effect.

It would therefore be useful to separately determine (and thus demonstrate) what the limiting resolution of a chosen system approach is. With system approach I mean camera system, film, and scanner, their combined MTF in understandable terms. There is a number of methods that could be used to quantify a few simple parameters that everybody can understand, complemented by visual confirmation.

I'm hinting at an Edge Spread Function (ESF) such as reported by the Imatest software as Edge response (1/3rd down the page), and based on a simple slanted edge that you can print yourself. There is also a slanted edge in my target which spawned a discussion here on LuLa, and it also easily allows to confirm correct focus. There is a number of LuLa forum contributors who could assist in producing that part of the data, myself included. The method also allows to detect sharpening artifacts such as halo. Since it quantifies a phenomenon in the spatial domain (pixels) it is not difficult to imagine such an edge even without knowledge of how to read MTF curves.

I think resampling would be quite acceptable for all viewers if the up/down sampling operation results in similar looking sharpness (the edge acutance and artifacts balance) if the systems were equally sharp. The only difference that then remains is the actual resolution differences, decoupled from the resampling method. So the resampling method should not introduce a new bias, but that may prove to be trickier than anticipated (e.g. Photoshop is pretty poor at downsampling without introducing artifacts).

The most neutral comparison is therefore to offer both, an upsample of the smaller sensor to the film scan PPI (the only variable introduced is the choice of upsampling algorithm for one of the sources, more about that later), and a downsample to the smaller output size (with the only variable introduced being the downsample algorithm used for the other source). That allows to only have a single variable added to one element of the mix, but both sides of the user spectrum (large output vs smaller output) can draw their own conclusions.

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I'm basically trying to avoid people saying "well you should have used Thromboid zero point resharpening with the inconvoluted zeta prime transform four paraboids below sigma 6 criteria" (obviously people may not use these words exactly but I hope you get the idea).


Exactly. Nobody can relate their own workflow to such a theoretically potential quality level, especially when it's only achievable under restrictive laboratory conditions, and depends on the phase of the moon. We all marvel at what rocket science brings, but we if we cannot afford or use it, it's only of theoretical interest.

However, that doesn't mean that lowest common denominator approaches are very informative either, because they introduce distracting artifacts. One could, as reasonable compromise, use resampling methods that are industry proven (e.g. such as implemented in ImageMagick). That will also avoid having to use commercial proprietary resampling algorithms, which may cut some corners for speed, or depends on other settings,  while hoping to hide the shortcomings for the uneducated public. The algorithms used by ImageMagick are publicly available and documented, and since the software is free, tests can be independently duplicated with the same results.

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We've also shot a scenic to get an idea of colour and real world use (it was a windy day on a cliff edge, just right to test the "you can't shoot 8x10 on a windy day" theory) and the P45+ (which we shot on a Linhof Techno with the 70mm Digaron WA) has a very different colour to the IQ180 (shot with an 80mm on a Phase 645 body). How would you normalise the colour? The IQ180 had a lot better colour in my opinion and tallied a lot closer with the Portra 400 and had a flavour of Velvia in there as well (at least you could get it looking at bit like Velvia which is near impossible with the P45+ as far as I could tell).

Color rendering and tonality differences are another hornet's nest. However, I do wonder how distractive the differences (after white balancing) are? You've seen them, and that perhaps raised the question. Do they appeal to someone's esthetic preference so much as to impede the ability to look past that quality and judge the other qualities?

Cheers,
Bart
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nazdravanul
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« Reply #22 on: October 27, 2011, 01:10:34 PM »
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I'm also looking forward to this Smiley . Please include the Aptus 80 in the mix, if possible ....
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Fine_Art
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« Reply #23 on: October 27, 2011, 01:40:10 PM »
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Dont worry about film grain. At a proper resolution it can be wiped out just like noise.

This is a noise ninja of a Fuji 800 Press shot. That has huge grain.
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Stefan.Steib
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« Reply #24 on: October 27, 2011, 03:10:23 PM »
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I'll save you the trouble, because here is the likely result:

1) If your processed IQ180 files look bad compared your processed 8x10 files, the digital folks will claim your digital processing was flawed, or that you didn't know how to optimally use the camera and/or lens and/or software.

2) If your processed 8x10 files look bad compared to your processed IQ180 files, the film folks will claim you used a bad camera or a bad lens, or bad technique, and/or had a bad lab process your film, and/or didn't know how to scan or the lab you used scanned poorly.

In short, you will spend a bunch of time and prove nothing except to yourself.  

And here is the bit that seals your fate: The fact you are already asking how to best process the Phase files does not bode well for the outcome...  

Sorry, but I am being realistic not pessimistic: It will be virtually impossible to perform the test in a manner that will satisfy both extremes, especially if you are not already a recognized expert in both 8x10 capture and scanning as well as an expert in digital processing using Capture 1.

Jack - wisely spoken, but I think itīs not getting to the minds of the participants here.
I still wonder how much time and effort some of you have to perform this kind of tests.

To me it is out of question that both approaches can result in stunning photographs that stand for their own.
It is also clear that film can do things that Digital cannot (yet) do and vice versa Digital has immediate access and other advantages that film does not have.

I understand that this is a technical forum, but as Jack already said: no matter what you will test - it will proof nothing or anything that anyone wants to hear or not to hear.

So the question here is what is the motivation?
Is there anything likely to be expected or a chance to expect the unexpected ?
 Huh

I know you guys will do it anyway. Have fun !   Smiley

Greetings from Munich
Stefan
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marcmccalmont
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« Reply #25 on: October 27, 2011, 03:13:51 PM »
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I would test an IQ180 with an excellent lens (rodenstock 70HR) mounted on a technical camera to 8X10 using an equally good lens for the test
The lenses are the limiting factor with the IQ180
Marc
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Marc McCalmont
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« Reply #26 on: October 27, 2011, 03:19:00 PM »
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Of course the film has to be a fine ISO 100 or less. Provia, Velvia and an Ektar for negative seems appropriate.
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Graham Mitchell
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« Reply #27 on: October 27, 2011, 03:36:47 PM »
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I would test an IQ180 with an excellent lens (rodenstock 70HR) mounted on a technical camera to 8X10 using an equally good lens for the test
The lenses are the limiting factor with the IQ180
Marc

Good point.
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Graham Mitchell - www.graham-mitchell.com
timparkin
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« Reply #28 on: October 27, 2011, 04:06:51 PM »
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So the question here is what is the motivation?

The motivation is to have one good test that addresses most of the concerns of both sides. Obviously some people don't want to know but I think they are vastly outnumbered that *are* interested. If you've already made up your mind then it's irrelevant however most people like to have some quality information about what the options are before they put down large sums of money. From my point of view I'm probably a rare person that has access to everything needed to do the tests and the time to do them because I run a magazine about landscape photography and I think it may be something our readers will be interested in.

Fundamentally though, my motivation is "I want to know".. and if I can share that then all the better.
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Fine_Art
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« Reply #29 on: October 27, 2011, 04:10:34 PM »
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Or why not to put down large sums of money!
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timparkin
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« Reply #30 on: October 27, 2011, 04:11:35 PM »
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Hi Tim,

I'm already looking forward to the results, as it seems to be a well managed and executed process done by openminded people who know what they're doing.

...

Bart

Hi Bart - we've got an Imatest Master license and have shot a slanted edge target as well as a couple of general resolution 'trumpets' :-)

Out of interest, I'm not sure what downsizing the higher resolution result to the lower resolution result is supposed to acheive - it sounds like throwing away information? I can understand that you end up comparing contrast at the highest MTF of the lower resolution result - is this all?
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timparkin
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« Reply #31 on: October 27, 2011, 04:24:12 PM »
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I would test an IQ180 with an excellent lens (rodenstock 70HR) mounted on a technical camera to 8X10 using an equally good lens for the test
The lenses are the limiting factor with the IQ180
Marc

We've used the 40 Digaron W, Schneider 35mm APO Digitar, Phase/Schneider 80mm f/2.8 and 70 Digaron W for the tests on Alpa WA, Cambo WRS, Linhof Techno and Phase 645 DF.

On the large format we shot a Toyo 810MII with a Fujinon 240A and APO Symmar 360.

The films used were Delta 100, Provia, Velvia, Portra 400 and Pro160S on the 10x8 - Delta 100, Provia, Portra400, Pro160S on the 5x4 - T-Max, Portra 400 on the 6x7 (we're shooting a Mamiya 7 with 55mm and 80mm lenses too).

The film is being assessed on a 100x stereo microscope and scanned on various scanners (including 8000dpi ICG and Aztek).

I'm very happy that the results are complementary to both systems though (i.e. they are both achieving near theoretical limits). There is still a lot to do before we publish though. We'll get something out at the end of November with commentary/analysis from various photographers and will be looking from considered feedback too.

Tim
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Mr. Rib
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« Reply #32 on: October 27, 2011, 05:36:27 PM »
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Thanks for your work Tim, eagerly waiting for the results!
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Stefan.Steib
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« Reply #33 on: October 27, 2011, 05:50:29 PM »
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Hi Tim

Understood - from this point it absolutely makes sense. It is giving you interesting content for your magazine.
Itīs also a service for many people who want to read this.

Just 2 questions: is there something you expect to find out ?
And  - do I understand this right- this test will not be published here, but in your Magazine exclusively ?

Greetings from Munich
Stefan
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Schewe
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« Reply #34 on: October 27, 2011, 06:01:32 PM »
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Out of interest, I'm not sure what downsizing the higher resolution result to the lower resolution result is supposed to acheive - it sounds like throwing away information? I can understand that you end up comparing contrast at the highest MTF of the lower resolution result - is this all?

Part of the issue when comparing different formats and media is the context in which you are judging the images. If the purpose is pixel peeping, that's fine, but an 8x10 scan at 4000ppi is gonna be huge on screen vs an IQ180...so looking at 100% or even 50% zoom isn't very practical...

From my point of view, the final arbiter for me is a final print...a given print size as a reference point at a certain PPI might give a better context. This would require downsampling the scan and upsampling the IQ 180 (depending on the "print size" you choose) but would help give a context for how the different images sources would work in print. Of course, then you get into the printer, the media and trying to show a print in a web based environment....can be done but it's a different can of worms (or the same can with different worms :~)
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timparkin
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« Reply #35 on: October 27, 2011, 06:16:40 PM »
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Hi Stefan,

Michael has offered to put the results up here but I imagine he will want to check them before he says yes. The results will also appear in the magazine for free and I'll be including additional content in the magazine (interviews with photographers about how they see the results, comparisons with DSLR's and medium format film cameras, essay about interpreting results and about why does it matter a damn in the first place, etc) some of which will be free, some free with subscription and the typically the longer essays and video/audio content is only available for paying subscribers. The key results regarding the 8x10 IQ180 comparison will be included for free on the magazine and will be available for Michael as well. We're hoping to get some commentary from some people who still use 10x8 and definitely will have some 4x5 and IQ180/P45+ users plus probably a few users of DSLRs and Medium Format film (we interviewed Jack Dykinga last week and he's an interesting example of someone who has moved from 4x5 to DSLR + tilt lenses.. )

As for something I expect to find out? Well I had my preconceptions that the IQ180 would out resolve 4x5 just but 10x8 would outresolve them both but not by the 2:1 ratio the increase in film size suggests. I also expected the results to appear very different and be quite intriguing to interpret (i.e. depending on what you look at the the 4x5 may end up outresolving the IQ180). I also expected to see some effects of the bayer algorithm come into play along with some low resolution results from film in the lower contrast parts of scenes.

However, I've got the first results back and I have to say I'm surprised by a few of the findings - more about that later of course :-) I know it's going to be 'controversial' but having engaged with both medium format digital back community and the large format community in advance, there shouldn't be too much to 'rationally' complain about from either side. Obviously there will be some small issues, it would have been nice to have a Sironar S 360 but I think the APO Symmar is probably outresolving the film anyway. I would have liked to have used a 240 Sironar S but the Fujinon has performed very well in some large group shots I had taken previously.

The one thing I would have liked to have done is to compare the IQ180 with the 10x8 with movements - however, so many people are using the Alpas and Cambos that it seems a fair test. We will definitely be putting the Linhof Techno + IQ180 up alongside the same Linhof and a P45+ and also an Ebony 45SU/180 Sironar S as part of a second test (my colleague Joe Cornish would like to find out the differences both in terms of resolution and aesthetics, as would I for that matter).  

Tim
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timparkin
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« Reply #36 on: October 27, 2011, 06:25:51 PM »
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Part of the issue when comparing different formats and media is the context in which you are judging the images. If the purpose is pixel peeping, that's fine, but an 8x10 scan at 4000ppi is gonna be huge on screen vs an IQ180...so looking at 100% or even 50% zoom isn't very practical...

From my point of view, the final arbiter for me is a final print...a given print size as a reference point at a certain PPI might give a better context. This would require downsampling the scan and upsampling the IQ 180 (depending on the "print size" you choose) but would help give a context for how the different images sources would work in print. Of course, then you get into the printer, the media and trying to show a print in a web based environment....can be done but it's a different can of worms (or the same can with different worms :~)

Hence the comment in the first post of the thread "We will be printing them as well but they will also obviously be displayed on screen for people to assess as most people won't be able to get to the 'show' we're hoping to give.". In terms of showing them on screen, it is up to the viewer to decide at what 'level' they want to assess the results. I would suggest a 100% on screen and then step away from the screen to about 10ft - this is really the only way to emulate a 300dpi print on screen. Viewing at 50% is OK for an indication but it doesn't emulate the very fine detail that may appear in a print. Viewing at any less than 50% is pretty pointless unless you are testing what the file will look like when printed well below it's maximum resolution.

I'm looking forward to hopefully getting some darkroom prints made as well if possible.

Tim

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Stefan.Steib
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« Reply #37 on: October 27, 2011, 06:54:12 PM »
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 Smiley  Tim

I admit this sounds like a lot of nice toys................
Ok - I am interested too....

greetings from Munich

Stefan
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Sheldon N
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« Reply #38 on: October 27, 2011, 07:06:44 PM »
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Very interested to see the results of this. Looks to be an extremely well thought out and thorough test.

Thanks for taking the time!
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Jack Flesher
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« Reply #39 on: October 27, 2011, 07:23:18 PM »
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I'm a bit dissapointed in that response to be honest Jack.
SNIP
You are a bright guy Jack, I was really hoping to get a useful response.

Tim

Tim,

Please understand I am not bashing you, your test or your method! I am simply stating that I believe regardless of whatever result you end up with, and no matter how well you controlled variables,  you are going to hear from folks on the "losing" side that are going to claim you did something wrong or did not do something you should have when capturing or processing their preferred medium.

You want helpful info, then here are a few basic questions to help start your thinking about some of the issues I see:

1) What aperture will you shoot the 40 HR-W and/or 70 HR-W at? (Optimal is probably ~ f8-11 for both.)
2) What aperture will you shoot the 240 Fujinon and/or 360 APO Sym 360 at? (Optimal is probably ~ f22-32 for both)
3) Assuming you will be photographing the same subjects from the same shooting distances with both systems, and assuming you will confirm precise focus with each before utilizing the image, how will you reconcile the differences in DoF between the 2 formats? (f8 on the 70 would require roughly an absurd f256 on the 360 for equivalent DoF at the same CoC's. However if you use 10x the CoC for the 8x10, then f8 on the IQ should be roughly equivalent to f32 on the 8x10.)
4) The 40 HR is roughly equivalent to a 180 on the 8x10, but you don't have a 180 for the 8x10 -- how do you plan to compare the 240 Fuji to the wider 40HR on MF?
5) The 70 HR is roughly comparable to a 300 on 8x10, but you don't have a 300, again, how do you plan on reconciling that subject magnification difference with your 360?
6) The 40 HR is outstanding and about "as good as it gets" for digital and has slightly higher resolution than the 70 HR (I currently own them both). The 360 APO symmar is outstanding or "as good as it gets" on 8x10, and better than the 240 Fuji (yes, when I shot 8x10 I owned both of those lenses too). So if you used the best of your list on each system, how do you reconcile the now more extreme FoV/magnification differences?

    
So I will submit that: Assuming you can somehow get to equivalent FoV's AND rectify DoF differences while using each system at optimal resolution apertures for each piece of glass (non-trivial to be sure), and assuming you can perfectly capture (relatively easy for the IQ, non-trivial for 8x10), AND perfectly process out each file to final digital file (a relatively easy step for direct digital if you do everything well at capture; more complex steps involved in getting the film processed and scanned, but certainly doable), then get those to as perfect as possible digital prints (relatively easy if you know what you're doing), AND then get as perfect as possible optical print from the 8x10 neg/tranny (non-trivial unless you have a truly stellar wet lab at your disposal) to compare, I think you will have a done an incredible service to the photographic community!  And I will even treat you to a steak dinner and fine bottle of wine to congratulate you Smiley

But... I still believe regardless of all of the above efforts, you will hear cries of "foul" from supporters of both sides regardless of how well you contain and control every aspect of your test.

Seriously, I wish you good luck and am happy to help in any way I can -- which at this point in time would be examination, processing and discussion of the IQ180 raw files, review of the final 8x10 scan file for comparative comment, and/or printing sections of each digital file for comparative review and comment of the respective (digital) prints.

Best,
« Last Edit: October 27, 2011, 09:29:16 PM by Jack Flesher » Logged

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