side by side comparison... large print digital back VS 4x5 color film

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Originally Posted by Ivan J. Eberle

Anyone care to comment on how a sampling frequency of between 2600 and 4000 ppi can be the wrong match for the grain structure of specific films?

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Can and did. Spent what feels like a whole friggin' day on it. Read the whole thread this time and you'll see it. For extra credit read the Vitale paper. There is no fixed "grain structure" to match. The film is not the problem.

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Originally Posted by sanking

Lenny,

Absolutely not. I am not saying that at all, and indeed am surprised at your confusion. I think we agree that some scanners deliver more real, effective resolution than others. Drum scanners, if calibrated, should deliver close to 100% of stated optical resolution. My EverSmart Pro delivers close to 95% of stated optical resolution. Most consumer flatbed scanners, Epson 4990, Epson V750, etc. deliver only about 40% of stated optical resolution. You can test this by scanning a high resolution target: you may have a pixel count of 4800 spi, but the effective resolution would be only about 40% of this, say about 40 lp/mm.

It is not a question of PMT versus CCD technology in the least. It is simply a question of understanding the fact that all pixels are not equal in terms of their detail/resolution. The concept of a "useful" pixel is only debatble if one has no understanding of what "useful" is.

Sandy King

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I'll be the first to say that understanding some of this is difficult. For one thing, we all talk about scans as if we are scanning a pixel - or a bit of the image. However, they are just reads, as in a value from 1-255 in lightness darkness for three different channels of color separated light.

I do understand the stated resolution issue. It shows up clearly in the Tango, which can do 11,000 spi, yet only resolve 4000. However, you have often said that your assessment of the real resolution of the 750, for an example, was around 2000 or so (don't remember the exact #). I understand that this is quite different from pixel count, and is not the stated resolution of 5300 or whatever... However, if it is true that it is at a true optical of 2000, the 2400 you stated as the max one could get from a 4x5 would be very close.

What am I missing?

Lenny

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Originally Posted by willwilson

A comment on the original topic... Based on Tim Vitale's article (which is worth reading) the approximate digital resolution of 4x5 Tmax 100 would be 9,700x12,200 pixels if your lens could resolve 70lpm. That's 118mp. This would equate to a 30"x40" print at 300dpi. Lenny, how do you get 320mp off of 4x5?

I would like to see a valid large print (30x40+) comparison as well; maybe 5DII, Phase One P65, and Top quality Drum Scanned 4x5 Tmax 100 and Velvia.

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I would be happy to show you such a thing. I have 32x40 images on my wall, come on by....

I scan 8x10's at 2666 and 4x5's at 4,000. The latter is 16,000 pixels by 20,000 pixels, or 320 mpixels. It think its pretty good, much better than 50 lpm would suggest. The scanner is rated at just under 8,000 ppi optical...

I don't know if that adds anything or not...

Lenny

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Originally Posted by Lenny Eiger

It shows up clearly in the Tango, which can do 11,000 spi, yet only resolve 4000.

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The Tango's 11 micron aperture would limit it to about 2200-2400 spi real optical resolution wouldn't it?

Lenny,

First, I think you are missing a lot .

As for the Tango resolution, no way the Tango has real optical resolution of 11,000 spi. The aperture of the Tango suggests no more than about 2500 spi. Of course, we know that is not bad since for many years Tango scans of transparencies were considered state of the art.

Sandy

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Originally Posted by Lenny Eiger

I do understand the stated resolution issue. It shows up clearly in the Tango, which can do 11,000 spi, yet only resolve 4000.
What am I missing?

Lenny

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Originally Posted by Bruce Watson

The Tango's 11 micron aperture would limit it to about 2200-2400 spi real optical resolution wouldn't it?

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Bruce,
I think something is missing here. Maybe its just something I don't understand. The Tango got a 4094 optical dpi at scannerforum.com, numbers I tend to trust. I think there is more than meets the eye. I think it has to do with the optics required to support a 6-micron engine. The Tango likely has a 6 micron capability, but they chose not to allow the aperture to vary, probably a software issue, I'm guessing, but the optics are still there that support it. 13 is better for almost everything, and they let color negs go and got everything else. Probably all about money or time, whatever.

I don't think resolution is closely related to the aperture setting. For instance, when I scan at 4,000 dpi at 13 microns, by rights I should get a lousy optical rez. There are only just 2000 13 micron slices per inch, but I get a much higher optical rez when I scan at the 4000 - from what I see I get at least the full 4000. I get maybe a few percentage points less than if I set it to match the dpi and aperture. But it doesn't cut itself in half. I have high suspicions that the idea that you can only get 8,000 ppi optical by scanning at 3 microns is entirely incorrect. It may be a little better if you do, but the grain anti aliasing will kill you. I doubt they made this error - I mean why bother with a 3 micron capability if there was no film that had a RMS Granularity to match it. It has to be to support the engineering.

Just my 2 cents,

Lenny

Lenny,

Curious, I thought the aperture setting was exactly the method that was used to determine resolution in ppi for drum scanners?


Sandy

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Originally Posted by Lenny Eiger

I don't think resolution is closely related to the aperture setting.

Lenny

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Originally Posted by sanking

Lenny,

First, I think you are missing a lot .

As for the Tango resolution, no way the Tango has real optical resolution of 11,000 spi. The aperture of the Tango suggests no more than about 2500 spi. Of course, we know that is not bad since for many years Tango scans of transparencies were considered state of the art.

Sandy

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Sandy,

I stated right there in my post that the Tango can only resolve 4000, not the 11,000.

I am enjoying this conversation, we have a group of very intelligent people here, discussing some very technical issues. It's great. I'm doing my best to listen - and learn. I am happy to admit what I don't know - and wanted to give you an opportunity to fill me in on something - as I don't see it the way you do. Instead, you take the opportunity to take a shot at me and suggest that I don't know jack.

Don't mistake being willing to listen with not knowing anything. I've been studying this stuff for a very long time and I've made a lot of great scans. I run 2 12 color printers and make all my own profiles, do all the stuff many others do. I know a great deal about all of this. I think there are some key things missing - that we are all missing. I don't think anyone here, including myself, has a grasp of it all, not even a full grasp of how scanners work. Even the great Phil Lippincott, who designed a huge amount of the technology we are talking about had limits when I talked to him about practical application. There aren't great books on the subject, that I know of, and there is no long "scanner school" which there used to be.

And now, once again, instead of discussing the issues, I have to take the time to defend myself against personal attack. I have to stand up and tell people all my experience, that I know a lot etc, and it stinks. Last week, you told people to "diss me" if I spoke up about flatbeds or some such thing. We have a conversation and you agree to disagree professionally and then you pull this crap again. You might have noticed that I have not said anything disrespectful to you - I have always disagreed with respect. I think we ought to stick with the issues.

Lenny

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Originally Posted by sanking

Lenny,

Curious, I thought the aperture setting was exactly the method that was used to determine resolution in ppi for drum scanners?


Sandy

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Yes, aperture largely determines resolution. However you can under or oversample so it does not necessarily determine ppi.

Lenny,

Excuse me, but you stated right here,

"I do understand the stated resolution issue. It shows up clearly in the Tango, which can do 11,000 spi, yet only resolve 4000."

Why would you say that the Tango can do 11,000 spi but only resolve 4000 and then complain because someone questions your language?

Get over your raw nerve. I have zero interst in attacking you personally and have not done so, and it is getting tedious having to explain to you otherwise.

Sandy King

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Originally Posted by Lenny Eiger

Sandy,

I stated right there in my post that the Tango can only resolve 4000, not the 11,000.

I am enjoying this conversation, we have a group of very intelligent people here, discussing some very technical issues. It's great. I'm doing my best to listen - and learn. I am happy to admit what I don't know - and wanted to give you an opportunity to fill me in on something - as I don't see it the way you do. Instead, you take the opportunity to take a shot at me and suggest that I don't know jack.

Don't mistake being willing to listen with not knowing anything. I've been studying this stuff for a very long time and I've made a lot of great scans. I run 2 12 color printers and make all my own profiles, do all the stuff many others do. I know a great deal about all of this. I think there are some key things missing - that we are all missing. I don't think anyone here, including myself, has a grasp of it all, not even a full grasp of how scanners work. Even the great Phil Lippincott, who designed a huge amount of the technology we are talking about had limits when I talked to him about practical application. There aren't great books on the subject, that I know of, and there is no long "scanner school" which there used to be.

And now, once again, instead of discussing the issues, I have to take the time to defend myself against personal attack. I have to stand up and tell people all my experience, that I know a lot etc, and it stinks. Last week, you told people to "diss me" if I spoke up about flatbeds or some such thing. We have a conversation and you agree to disagree professionally and then you pull this crap again. You might have noticed that I have not said anything disrespectful to you - I have always disagreed with respect. I think we ought to stick with the issues.

Lenny

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