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Author Topic: Backs and LF films resolution according to Burtynsky  (Read 19504 times)

fredjeang

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Re: Backs and LF films resolution according to Burtynsky
« Reply #20 on: November 15, 2010, 06:03:46 pm »

Could anybody with high sense of compassion for the non-harvart members could traduce those graphics into a decent and resumed english?
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ErikKaffehr

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Re: Backs and LF films resolution according to Burtynsky
« Reply #21 on: November 16, 2010, 12:44:14 am »

Hi,

When Charlie Cramer switched from 4x5" to to P45 he found that the P45 was a decent match for drum scanned 4x5" Velvia. The P45 is at 39 MP. 8x10" has four times the area compared to 4x5" so it is plausible that 160 MP may be needed to match it. On the other hand, large format don't have the MTF at high frequencies that DSLR lenses are the best of crop of MF lenses. Still, to compete with a 8x12" lens that performs decently at 20 lp/mm we would need an MF lens that has equivalent MTF at 80 lp/mm. On the other hand, 8x10" lenses are often used at f/22. At f/22 resolution and MTF are cut to half compared to f/11. So would we use a perfect lens on at f/11 on 4x5" and a similarly perfect lens on 8x10" at f/22 they would be equal in resolution and MTF (ignoring MTF of the film).

With digital sensor is replaced by film. We would need a perfect lens at f/5.6 to match the perfect 8x10" lens and of course "nail focus", avoid vibrations and so on.

I guess that some of the Leica lenses Rodenstock Apo Digitars are pretty close to perfect lenses. But we are talking expensive stuff.

There are many other aspects. Film flatness to begin with, focusing accuracy which may be easier to achieve at f/22 than at 5.6, vibrations, wind sensivity.

Best regards
Erik


I found a Burtynsky interview where he was explaining that the digital backs are going to pass the 100MP barrier ( 120 MP ) and when that will happen it will overcome the current large format film resolution.

So if I understand Burtynsky well, the current digital backs are still not capable of surpassing the 8x10 films resolution until they will reach 120MP. But it seems that his affirmation is contradicting the "datas that are disponible" in internet.

It would be nice if large format film users who also work with high end backs could comment on that matter.

Is the Burtynsky statement correct?
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Erik Kaffehr
 

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Re: Backs and LF films resolution according to Burtynsky
« Reply #22 on: November 16, 2010, 01:38:37 am »

Could anybody with high sense of compassion for the non-harvart members could traduce those graphics into a decent and resumed english?

Basically I'm just trying to justify my purchase of two apo-sironar-s lenses!  (They're my most expensive lenses.)

In other words, I've found that while they perform unremarkably over a small area of the frame (at least by small format standards), the full image still looks great.  Due to the increased sensor size (16 times the surface area of 135 film or an FX digital sensor), they only need to perform 1/4 as well as a dslr camera lens or 1/3 as well as a lens for 645 to give the same contrast and detail to the given frame size.  And, according to mtf charts, they perform at least 1/4 to 1/3 as well as the very best!  Which sounds terrible (and kind of is), but is pretty good in practice, since they're less expensive than the very best and allow for generous lens movements.  And by normal working apertures (f11-f32 depending on focal length) you're losing most of your resolution to diffraction, not lens flaws, anyway.

That's why Rodenstock's digital lenses are so much more impressive.  They bring the coverage down to a much smaller area and then increase the mtf accordingly.

Anyhow, the rough equivalency between 50 megapixels and 4x5 sounds perfectly reasonable to me based on prints I've seen.  4x5 should have the ability to hold a tiny bit more fine detail as per its own mtf charts, but digital looks sharper than film and lacks grain.  I have been really impressed by the 8x10 enlargements I've seen.  They put 4x5 to shame, but mostly in terms of tonality, not contrast.  100 megapixels could likely match that, though, but with a different "look."  Stitching might be the ultimate solution, if the scene permits.
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Rob C

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Re: Backs and LF films resolution according to Burtynsky
« Reply #23 on: November 16, 2010, 10:28:46 am »

I guess that some of the Leica lenses Rodenstock Apo Digitars are pretty close to perfect lenses. But we are talking expensive stuff.

There are many other aspects. Film flatness to begin with, focusing accuracy which may be easier to achieve at f/22 than at 5.6, vibrations, wind sensivity.

Best regards
Erik




Maybe not: as I understood it from night school, depth of focus at the film (not depth of field at the subject) is also a variable, with longer lenses having more available depth of focus (at the film plane) than do shorter ones, which flies in the face of what's usually expected. So, with larger formats using relatively longer lenses to cover the same angle of view and with those lenses being slower, maybe the ease of focussing the larger format having to use a smaller aperture to do so is similar to the problem that MF digi cameras seem to have finding correct focus at near-infinity, but for the opposite reason: with the large film there is too much depth to determine, with slower lenses, what's exactly the point of focus, and with the digi there's not enough to permit making the choices accurately even with faster lenses...

Always liked the basic split-image viewfinder in the Fs!

Rob C

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Re: Backs and LF films resolution according to Burtynsky
« Reply #24 on: November 16, 2010, 10:42:35 am »

So can we sum up the approximate equivalences? Would this be about right, or is there any consensus?

1) 20+ MP FFDSLR ~ 645 film
2) 16.7 MP (37x37 mm) MFDB ~ 6x6 film [fewer pixels than the FFDSLR, but no AA filter, and >50% larger sensor]
3) 18 - 28 MP (33x44 mm) MFDB ~ 6x7 film [only very marginally larger CCD size than the 37x37 mm ones]
4) 60 MP (54x40 mm) MFDB ~ 4x5 film [nearly 4x more pixels and 4x more film area than the 16.7MP/6x6 case...although nowhere near 4x the CCD size, less than 2x in fact]
5) 150?? MP (70?? x 55?? mm) MFDB ~ 8x10 film [surely it will have to be a substantially larger digital sensor than 645...they can't keep dicing 645-format into ever smaller pixel units and call it "8x10"?!]

Anyway speaking from my own experience, I own a 37x37 mm MFDB and it does seem to match anything I did previously with 6x6 film.

Ray
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Dick Roadnight

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Re: Backs and LF films resolution according to Burtynsky
« Reply #25 on: November 16, 2010, 12:26:52 pm »

So can we sum up the approximate equivalences? Would this be about right, or is there any consensus?

4) 60 MP (54x40 mm) MFDB ~ 4x5 film [nearly 4x more pixels and 4x more film area than the 16.7MP/6x6 case...although nowhere near 4x the CCD size, less than 2x in fact]
5) 150?? MP (70?? x 55?? mm) MFDB ~ 8x10 film [surely it will have to be a substantially larger digital sensor than 645...they can't keep dicing 645-format into ever smaller pixel units and call it "8x10"?!]
Ray
If a 50mm sensor is equivalent to 5*4, you might need a 100mm sensor for 10*8, but an 8 micron 16 shot might give the best res/mm^2.

You might think that they will have to invent a camera bigger that 645, but the Sinar P3 etc. 10*10 lensboard cameras could house a sensor about 9*9cm, which would be a useful use of existing technology and a good compromise res/size/weight/cost. If you send me one on permanent load to test, I will not charge you for the idea!
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JdeV

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Re: Backs and LF films resolution according to Burtynsky
« Reply #26 on: November 16, 2010, 02:07:31 pm »

From my own experience shooting architecture/travel:

1) A P45+ is marginally superior in resolution to a scanned 4"x5" negative.
2) Three vertical P65 shots stitched together, with around 25% overlap, to yield a file of approximately 120MP, resolve significantly less than an 8"x10" scanned transparency and even a bit less than an 8"x10" scanned negative. This is with the very best current Rodenstock HRW lenses and very careful technique (tethered, digitech, weighted tripod etc.).
3) The P65 is significantly more colour accurate than film and terrific in mixed lighting conditions.
4) The scanned negative is way better for holding highlight detail and though not actually very colour accurate generally looks great once worked on in a way that is hard to achieve with digital. However, to get the most out of it one needs to produce 'raw' 16-Bit scans and the files are very demanding of Photoshop skills and very time consuming to spot.
5) Even though I generally apply grain to digital images a scanned negative has more grain than I would choose.




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ErikKaffehr

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Re: Backs and LF films resolution according to Burtynsky
« Reply #27 on: November 16, 2010, 04:03:30 pm »

Hi,

At large camera subject distance I'd assume that Depth Of Focus is only dependent on f-stop. See it as a cone of light exiting the lens. I presume that you would focus at near maximum aperture and stop down to f/22 where a large format lens seems to perform best. At large apertures on DSLRs focus shift may be a problem.

Best regards
Erik




Maybe not: as I understood it from night school, depth of focus at the film (not depth of field at the subject) is also a variable, with longer lenses having more available depth of focus (at the film plane) than do shorter ones, which flies in the face of what's usually expected. So, with larger formats using relatively longer lenses to cover the same angle of view and with those lenses being slower, maybe the ease of focussing the larger format having to use a smaller aperture to do so is similar to the problem that MF digi cameras seem to have finding correct focus at near-infinity, but for the opposite reason: with the large film there is too much depth to determine, with slower lenses, what's exactly the point of focus, and with the digi there's not enough to permit making the choices accurately even with faster lenses...

Always liked the basic split-image viewfinder in the Fs!

Rob C
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ErikKaffehr

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Re: Backs and LF films resolution according to Burtynsky
« Reply #28 on: November 16, 2010, 04:26:27 pm »

Hi,

I made some tests comparing Velvia in a Pentax 67 with an FF DSLR with 24.5 MPixels. What I found that the Velvia may have better resolution on high contrast detail than the FF-DSLR but the digital image generally was much easier to work with. Better DR, less noise better color. Also, when sharpness was evaluated using Imatest I found the FF DSLR significantly better den Velvia on 67.

My findings are here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/16-pentax67velvia-vs-sony-alpha-900


Knowledgable photographers like Charlie Cramer have found the Phase One P45 at 39 MPixel to be comparable with Velvia on 4x5", check here:

http://www.outbackphoto.com/artofraw/raw_28/essay.html

Charlie Cramers findings actually would indicate that 67 would be more like 12 MPixels, as 4x5 film is about 1.8 times larger than 67 film along one side. So is 39 MP equivalent to 4x5" than 6x7cm would correspond to 39/(1.8*1.8) -> 12 MP.

One of the advantages of digital images over film is that the digital image is generally quite smooth, specially at low ISO. Although early DSLRs had only 3 MP in resolution they were perceived competitive with film, although they lacked the actual resolution but the image structure was much smoother.

Whatever equipment we use, image quality is dependent on much more than sensor or film resolution. Only with exacting work can maximum performance be achieved.

Best regards
Erik

So can we sum up the approximate equivalences? Would this be about right, or is there any consensus?

1) 20+ MP FFDSLR ~ 645 film
2) 16.7 MP (37x37 mm) MFDB ~ 6x6 film [fewer pixels than the FFDSLR, but no AA filter, and >50% larger sensor]
3) 18 - 28 MP (33x44 mm) MFDB ~ 6x7 film [only very marginally larger CCD size than the 37x37 mm ones]
4) 60 MP (54x40 mm) MFDB ~ 4x5 film [nearly 4x more pixels and 4x more film area than the 16.7MP/6x6 case...although nowhere near 4x the CCD size, less than 2x in fact]
5) 150?? MP (70?? x 55?? mm) MFDB ~ 8x10 film [surely it will have to be a substantially larger digital sensor than 645...they can't keep dicing 645-format into ever smaller pixel units and call it "8x10"?!]

Anyway speaking from my own experience, I own a 37x37 mm MFDB and it does seem to match anything I did previously with 6x6 film.

Ray
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Erik Kaffehr
 

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Re: Backs and LF films resolution according to Burtynsky
« Reply #29 on: November 17, 2010, 04:17:56 am »

The question for the ultimate resolution on image capture devices can be fascinating. But there is no definite answer. Before I elaborate on the subject I'd like to point out that the fundamental  difference in character of the capture medium and how it supports your vision will have a much greater impact on your imagery than some resolution advantage of one over the other.

Film resolution depends to a very large degree on the incoming contrast. If you have a line target of 2-3 stops contrast a good standard 135 format lens will be able to put down more than 100 lp/mm on most modern films. We have tested many films and verified the results by inspecting the film under a microscope. But if you have low contrast detail only separated by a small fraction of a stop your resolution on film might drop to just 20-50 lp/mm. I haven't made proper tests for low contrast resolution so this number is just an experienced guess.
Digital image sensors are highly efficient at detecting very low contrast levels. Thus their resolution only depends to a small degree on image contrast. The Bayer pattern may reduce the resolution in certain conditions depending on the color of the incoming light, the internal signal processing and the demosaicing algorithm.

On the question of how many MP you need to get all the detail in a perfectly exposed 8x10" film I can say that I usually drum scan mine at 3600 ppi to roughly 950 MP (almost 6 GB per image) which seems to be overkill. Of course at this resolution the image is not as sharp compared to the pixel level of a MFDB. But sometimes on high contrast structures there's so much detail on the film that it takes such pixel density to capture it. What's more important, if you're in for a very large prints, I'm talking about 72x92" lighjet at 300 ppi or 64x82" inkjet at 360 ppi, there are smoother  tonal transitions compared to scans of lower resolution. So when large prints are in order it's always better to have these transitions optically scanned instead of relying on software interpolation. When I'm scanning I'm really trying to get all the information there is on the film down to the grain structure. I could post some samples if there's interest.
I think digital systems need to increase their sensor size to get in 8x10" territory. I'm not sure how much the sensel density can be increased without losing too much quality on other parameters besides resolution.

Common working f-stops on 8x10" are in the f/22 - f/45 range where you can get diffraction limited resolution on film. Shooting indoors DOF might even call for f/64. When you're not focus stacking DOF requirements can be the limiting factor for resolution.
If you do not intend to print overly big the large film format can be quite forgiving. And you can get pretty decent results from lower end scanners. A scan of only 1200 ppi already gives you 100 MP. It's a long range from pretty decent to the full potential of the format. For smaller formats that range is more narrow but when you intend to process digitally starting with a great scan to gives you some meat to work with. Speaking of scanners, Charles Cramer used a Tango drum scanner to come to his conclusions about 4x5". Although the Tangos are great pieces of equipment they lack the resolution to make use of the full potential of even 4x5".
One of the advantages of working with film is its scalability. You can scan the film or enlarge it to your desired print size and still get something real out of it even if it is just the physical material itself. With digital you're stuck with what you've got at the capture stage.
 
Erik, if you take the best commercially available lenses for different image formats and compare the MTFs and normalize the resolution with the image circle you can see that there's only a very slight advantage for larger formats. By normalization I mean for example to compare the 80 lp/mm graph of a 90mm digital MF lens over an 80mm image circle and the 20 lp/mm graph of a 360mm lens over a 320mm image circle. Checking the manufacturer's recommended working apertures is also a good indication that there's only a slight increase in overall lens performance for larger formats.
But for smaller formats it takes a much higher resolution capture medium to get all the detail that a top of the line lens can deliver. The larger the format the closer you can come to diffraction limited photography.

-Dominique

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Re: Backs and LF films resolution according to Burtynsky
« Reply #30 on: November 17, 2010, 05:53:39 am »

I had my portfolio slapped down by Nadav Kander's agent earlier this year because I shot on MF digital rather than 5x4 film. 

What she said was interesting, and something rarely discussed on forums like this which are essentially gear focused.

"With large format film you make different choices"  was what she said.

I hated this, but on reflection, I decided she was right and wrong at the same time.  I also decided that the machinery used was unimportant. Its the choices that are important. With this in mind I decided to leave my last two boxes of Provia 5x4 in the fridge and continue with digital.

Whatever technological objections or reasoning you apply, there will always be a place for different media in photography, and mostly it won't matter anyway, not to me. I prefer interesting pictures badly made to boring pictures made beautifully. If I was rich or very successful I'd buy an Aptus-II 12 because I could make technically better images than I can with 5x4 or 8x10 film. No contest, but it wouldn't make my pictures any better.





 


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jduncan

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Re: Backs and LF films resolution according to Burtynsky
« Reply #31 on: November 17, 2010, 07:21:46 am »


"With large format film you make different choices"  was what she said.

I hated this, but on reflection, I decided she was right and wrong at the same time. 
I dont understand what she means. The difference she talks about is bwt film and digital, or is she talking about different types of film or what?
If the difference is digital vs film I cant see her point.
Since when different become better? Does she really believe that the same pro photographer will make a different composition with digital or film?
Of course if a photographer  is starting his/her path or are in the middle of a reinvention  the MEDIA will contribute to the construction of the new style a lot. But I guess this was a paid job, not and artistic journey so I fail to see her point. The places I can see where digital vs film produce different results (compositions) are the ones where the Photographer can't control the light and there is some action. And nowadays that case favors digital big time.
That doesn't mean she dont have a good point or even a veery good point. Is just that I am failing to see it.
Could you elaborate your inside in the meaning?
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Re: Backs and LF films resolution according to Burtynsky
« Reply #32 on: November 17, 2010, 08:48:30 am »

I prefer interesting pictures badly made to boring pictures made beautifully. If I was rich or very successful I'd buy an Aptus-II 12 because I could make technically better images than I can with 5x4 or 8x10 film. No contest, but it wouldn't make my pictures any better.

A kindred spirit...
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Dick Roadnight

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Re: Backs and LF films resolution according to Burtynsky
« Reply #33 on: November 17, 2010, 10:04:40 am »

Digital image sensors are highly efficient at detecting very low contrast levels. Thus their resolution only depends to a small degree on image contrast. The Bayer pattern may reduce the resolution in certain conditions depending on the color of the incoming light, the internal signal processing and the demosaicing algorithm.
-Dominique

Does nobody use Bayer-free-multi-shot?
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JdeV

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Re: Backs and LF films resolution according to Burtynsky
« Reply #34 on: November 17, 2010, 10:25:39 am »

So when large prints are in order it's always better to have these transitions optically scanned instead of relying on software interpolation. When I'm scanning I'm really trying to get all the information there is on the film down to the grain structure. I could post some samples if there's interest.

Please do so if you can find the time. I am sure there would be a great deal of interest.
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Re: Backs and LF films resolution according to Burtynsky
« Reply #35 on: November 17, 2010, 10:42:35 am »

Quote
. . . digital backs are going to pass the 100MP barrier ( 120 MP ) and when that will happen it will overcome the current large format film resolution.

To me, the resolution isn't as important as the camera movements. I find it much more difficult to get accurate camera movements on a small digital back than on an 8x10 or 4x5 camera.
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Re: Backs and LF films resolution according to Burtynsky
« Reply #36 on: November 17, 2010, 10:53:54 am »

[quote author=SCHWARZZEIT link=topic=48241.msg402747#msg402747 date=1289985476
 
Erik, if you take the best commercially available lenses for different image formats and compare the MTFs and normalize the resolution with the image circle you can see that there's only a very slight advantage for larger formats. By normalization I mean for example to compare the 80 lp/mm graph of a 90mm digital MF lens over an 80mm image circle and the 20 lp/mm graph of a 360mm lens over a 320mm image circle. Checking the manufacturer's recommended working apertures is also a good indication that there's only a slight increase in overall lens performance for larger formats.
But for smaller formats it takes a much higher resolution capture medium to get all the detail that a top of the line lens can deliver. The larger the format the closer you can come to diffraction limited photography.

-Dominique

[/quote]

Please can you expand on this. From my own tests it is striking how the best large-format film lenses approach their diffraction limit at their working apertures. The best medium format lenses for SLR systems are only marginally better at their working apertures and do not approach diffraction limit. Given the substantially larger area of 4"x5" and 8"x10" to even 6x7, let alone the <645 of medium-format digital, this presents a considerable overall optical advantage to larger formats. Of course resolution is not purely a matter of optics and there is significant resolution loss from film/scanning as opposed to sensor capture.
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Jack Flesher

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Re: Backs and LF films resolution according to Burtynsky
« Reply #37 on: November 17, 2010, 01:46:03 pm »

My own .02 from experience:

1) It's extremely difficult to get a "perfect" LF film capture.  First off, film flatness is an issue, second, precise focus requires that your GG is in perfect alignment with the surface of the film in your film holder.  And film holders can vary in film plane by several thousandths of an inch.  And then film rarely is perfectly flat in the holder.  

2) 8x10 is even less accurate in the above respects than 4x5 but;

3) It is much easier to critically focus the larger 8x10 image accurately as it has more CoC tolerance to begin with; even more so with 4x5 compared to current 6x45 MF.

4) Example: When I had my Betterlight scanning back, I could "see" where a 0.5mm change in focus extension would alter the exact PoF from a 210mm lens at f11 from 100 meters down to 10 meters...

5) Glass becomes a limiting factor as you move up in format as well, and this removes a significant portion of the "4x gains" in film area from 8x10.  My best 4x5 lenses rendered as high as I could measure them, which was around 60 lpmm centrally (arguably these lenses could be rendering as high as 90 lpmm, but I couldn't confirm that with my test equipment); by comparison my best 8x10 lenses were in the mid 40's with one hitting 52 centrally.  Clearly there are exceptions here in both directions, but I think these are pretty "comfortable" resolution numbers to use as a generalization from the best modern LF glass.  

6) By contrast, I own MF lenses that clearly still resolve beyond a pixel on my MFDB which has a 6u pixel pitch.  6u pixel resolution basically means the sensor is theoretically capable of resolving a little over 80 lpmm for a linear black and white line pair, or around 55 if you go with Nyquist.  

My own "conclusion" on how many pixels it took to match each medium, assuming the best possible glass being used for all mediums, was ~~50MP to match a perfectly captured and scanned sheet of 4x5 and ~~100MP to match a perfectly captured and scanned sheet of 8x10.  Corollary comment here is even when taking extreme care in my set-ups, I got maybe a 30% hit on the "perfectly captured" part for either 4x5 or 8x10. Not saying the other 70% were unusable, far from it -- just not "perfect."  (I had a much higher hit rate with the Betterlight because it had electronic focus confirmation and was of course a perfectly flat capture plane.)  

For comparison, with my current MF digital set up, I find my DF body's auto focus to be more accurate a far higher percentage of the time of the time than I ever was with a 10x loupe and a GG, and of course obtaining correct exposure is immediately confirmable.  Thus, I'd give my current 60MP MFD set up a quarter notch over 4x5 most of the time and maybe rate it a half notch behind my best 8x10 captures.  Of course as soon as you factor in convenience, the film solution drops way down the ladder for me.  

In the end, my own opinion is if you want to deal with it, 4x5 and 8x10 film still offer a very viable solution for generating the highest quality captures.  

Cheers,
« Last Edit: November 17, 2010, 02:00:03 pm by Jack Flesher »
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PaulSchneider

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Re: Backs and LF films resolution according to Burtynsky
« Reply #38 on: November 17, 2010, 02:14:44 pm »

Dominique,

since I gather that you have one of the world's finest drum scanners, would you mind posting a 100% crop, say 2-4 megapixels in size, of a 6GB 8x10 scan?

I would like to compare it to some 100% crops of mfdb shots made with technical cameras.

I have never seen a scan of this type and am very curious as to what the top end of drum scanners can extract at this point.

What is the file resolution of such a 6gb scan?

Kind regards

Paul

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Re: Backs and LF films resolution according to Burtynsky
« Reply #39 on: November 17, 2010, 02:29:42 pm »

[quote author=Jack Flesher link=topic=48241.msg402845#msg402845
My best 4x5 lenses rendered as high as I could measure them, which was around 60 lpmm centrally (arguably these lenses could be rendering as high as 90 lpmm, but I couldn't confirm that with my test equipment); by comparison my best 8x10 lenses were in the mid 40's with one hitting 52 centrally.
Cheers,
[/quote]
...so, if we want a really large print, and Apo-Digitars do not have enough image circle, shift-and-stitch on 5*7 with a good LF lens is a viable option, and a good alternative to pan-and-stitch?
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