How many ppi is enough for scanning 35mm?

[alan_rockwood]

<p>Good post David.</p>

[david_goldenberg1]

<p>Oops! I wrote the equation incorrectly. The correct form is:<br>

b_total = sqrt(b1^2 + b2^2)</p>

[alan_rockwood]

<p>Yes, David's second equation is correct.</p>

<p>In fact, if one takes the standard deviation as the width of point spread functions then the equation is a rigorously correct way to combine point spread functions, assuming the point spread functions are statistically independent.</p>

[david_goldenberg1]

<p>I should also have said that the graphs were drawn with the correct equation. <br>

The basic assumption is that the point spread function (the form of the blurriness) can be approximated as a Gaussian function, a "bell-shaped" curve. As Alan suggests, this will be the case if the point-spread function has an origin from random noise, but the Gaussian is also commonly used as an approximation to the point-spread function of a diffraction limited lens.<br>

David</p>

[alan_rockwood]

<p>Actually, David's formula is true for combining any two probability distributions, provided each of the two functions have a standard deviation. (There are some valid probability distributions that do not have a standard deviation, the Lorentzian function being the best known.)</p>

<p>There is a theorem from probability theory that the standard deviations of a function that results from the convolution of two functions is equal to the square root of the sum of the squares of the standard deviations of the two combining functions. The two combining functions don't have to be Gaussian, and the two combining functions don't even need to be of the same functional form. The theorem is very powerful.</p>

<p>The result does not necessarily hold for combining other measures of distribution width, such as full width at half max.</p>

[mauro_franic]

<p>I'll share some simple facts.</p>

<p>1 - The Coolscan 9000 captures detail very close to its nominal resolution (4,000 dpi - full RGB) with excellent DMAX, low noise, ICE (color) and speed.<br /> 2- High frequency and high contrast detail (e.g. tree branches, hair, small lettering, etc) on most of the films I use exceed 4,000dpi (this is measured by me not by quoting other people's work). In these cases, TMAX aproaches 6,000 dpi - Velvia 4,500 dpi - Ektar 4,200 dpi - TPan 7,000+ dpi.<br /> 3- Most landscape pictures will show this kind of detail in some areas. In real life with my pictures.<br /> 4- From 6x7 film + Coolscan, the resolution of the scanner becomes the limiting factor on prints larger than 30x40. I print larger than 30x40 - especially on canvas since I don't like to mirror the edges for gallery wrap. <br /> 5- It is a silly fallacy that large fine art prints are not observed up close. Most people given the chance will dive into the detail of a large interesting print as long as the overall composition is attractive. Because of this, I evaluate pictures on both, a small 2"x2" print first and then a crop at full size before committing to the print.<br /> 6- Scanning should always be done at the max resolution/quality possible before editing since you don't want to double up the work if you decide to print/sell. Also the film is always cleaner before putting into a sleeve.<br /> 7- Photography has an awesome combination of art and science and cannot stand by itself with just one of the two.</p>

<p> </p>

[scott_ferris]

<p>Those are not simple facts, they are opinions.</p>

[mauro_franic]

<p>What is not a fact Scott?</p>

[scott_ferris]

<p>I think all 7 points. They are your opinions for your work and the way you choose to do it. They are not proven substantiated generally accepted facts.</p>

<p>I would agree with number 5, but never having seen an independent paper on art and viewing distances, it is not a verifiable fact, just a personal observation.</p>

[mauro_franic]

<p>I won't really argue much on these things as they are objective but I can offer you test data, films and scans personally if you are interested.</p>

<p>1. In addition to the independent tests available, I have verified the Coolscan results myself. If you are interesed email me and I will share the results.<br>

2. Same as above and I can send you direct pictures of the film that show more resolution than the 4,000 dpi the Coolscan can capture. Or more easily, since the Coolscan tops out close to its 4,000 dpi when scanning several different films - it is clear without the necessity of a microscope that the Coolscan - not the film - is the limitation.<br>

3. Nature is analog and fine details like small tree branches, hair, etc also provide detail beyond 4,000 dpi.<br>

4. 30x40 prints from a Coolscan is about 300 dpi. You may print a scan from my website at different resolutions and observe that over 300-360 dpi, a pigment (Epson in my case) becomes the bottle neck and below 300 dpi the scan is the bottleneck.<br>

6. Editing twice takes additional work. Film may get additional scratches or particles from going into a sleeve.<br>

5 and 7. Not much to add.</p>

 

[scott_ferris]

<p>Ah, thats the spirit, so they are no longer categorical facts. With regards objectivity, I have argued your objectivity and results before, so please don't elaborate.</p>

<p>These stated facts are your opinions. Your workflow heavily favours your techniques and results, and you have a very large pair of rose tinted glasses, often those results do not align with others opinions or results.</p>

[mauro_franic]

<p>Email me if you would like me to send you any of the film or scans for the tests.<br />My results are consistent with everyone else's Coolscan results (including the OP's link <a href="http://www.filmscanner.info/en/NikonSuperCoolscan9000ED.html">http://www.filmscanner.info/en/NikonSuperCoolscan9000ED.html</a> ). If your results are different please post them.<br>

I will respond to you if you have specific questions you would like me to answer.</p>

[bob_meyer6]

<p>Pixel Peeping in a good way? No, I don't think so. My point is that looking at a tiny section of an image at a magnification that no one would ever use to look at an actual photograph is an interesting exercise, but not terribly relevant. That fact that you can see additional detail at, say, a 60x enlargement doesn't mean you'll be able to see it in a 16x20 or 20x30 print.<br>

Science and truth are fine, but the truth isn't always relevant. A Ferrari with 600 HP will probably be faster than a similar Ferrari with "only" 500 HP. But both will exceed the performance that one can actually make use of on public roads. Similarly, if 4000 dpi contains all the detail you can see in the size of print or display you'll actually use, the extra detail captured at 6000 dpi may not be relevant "on public roads."</p>

<p>MF film cameras could always out resolve 35mm film cameras, and 8x10 film out resolve MF; but for the vast majority of uses 35mm was "good enough." I suspect that for the vast majority of uses 4000 dpi is "good enough." Whether that is true or not isn't apparent based on this test.</p>

[mauro_franic]

<p>Bob, you are correct, for most applications the Coolscan 9000 is good enough. I wish it were 6,000 dpi but 4,000 dpi with very high dmax, ice and low noise for medium format for the Coolscan gives me great results at any print size.</p>

<p>Would 6,000 dpi be better? Yes. Actually, in my opinion, 6,000 dpi would be just about ideal.</p>

[alan_rockwood]

<p>Bob,</p>

<p>So getting better quality by going to a larger format is good, but it is not good to try to get better quality by staying within a given format by going to a higher technical standard, e.g. higher resolution scans? OK, if that's the approach you want to take then fine, different strokes for different folks, but that does not invalidate those who would take a different approach.</p>

<p>In any case, I started this thread to deal with a technical question, which is how many pixels are enough (in a technical sense) to capture all the detail in a 35mm scan. Some would prefer to turn the question into one of aesthetics (i.e. better resolution is not an aesthetic need), which was not the original question, or a value judgement (i.e. how good is "good enough"), which again was not the original question.</p>

<p>Those are all valid issues for some people to discuss, and you are all free to discuss them if you want, but make no mistake; those side questions are off topic and probably deserve threads of their own.</p>

[scott_ferris]

<p>From a scientific point of view, best guesses by truly world recognised authorities on the subject suggest that to resolve film grain not just recognise it, thereby <em>"leaving nothing on the table"</em>, 10,000 to 15,000 ppi is the figure needed to scan film. Anybody who wants to contradict the opinion of Bruce Fraser is either very brave and needs the background and facts to back it up, or is stupid. What that gives you is detail of the grain structure, that is needed to never leave anything behind.</p>

<p>Of course currently that is an impractical figure, for so many reasons, equipment, technique, storage, file handling, costs etc etc. What it also does is ask a multitude of further questions you don't want discussed. The biggest of which for me would be, why bother? You are looking at the final few percent in an increasingly steep curve of technical difficulty and impracticality. From a technical level that is what you need to do, from almost any aesthetic, practical or useful standpoint it is not, the figure everybody else is looking for is what is needed for there use.</p>

<p>So 10,000-15,000 ppi. But then I linked to a reputable source for that four days ago.</p>

[lenny_eiger]

<p>Alan,<br>

To leave nothing on the table, its the technology that's important. PMT's are far more sensitive than CCD's. (It's Physics.) That means drum scanner. The two top scanners are the Aztek Premier and the ICG 380. The next thing you need is an experienced operator who listens to you, looks at what you are looking for and makes sure you get it. Of course you can learn to do this yourself, but it takes a little doing. To get enough from 35mm to do some real quality I'd go with the Premier any day...<br>

And to be totally up front, yes, I have one. I am biased, as it continues to amaze me (and my clients).<br>

Lenny</p>

<p>EigerStudios<br>

Museum Quality Drum Scanning and Printing</p>

[mauro_franic]

<p>Alan, I posted this test to help answer your question:<br>

http://www.photo.net/film-and-processing-forum/00ZPRA</p>

 

[p.d._foote]

<p>I've tried parallel & serially hooking up 3 azteks(ran out of money) & still can't get the clarity I need at the molecular level of the 35mm panatomic X I have from the 60's. Someone suggested contacting Stanford, but I'm afraid that with the Higgs Boson particle still unresolved it may be a futile endeavor anyway. Getting back to photography I guess for now I will stick with Minor White's idea that for technical data- the camera was faithfully used. Regards to all, Paul.</p>

[alan_rockwood]

<p>Paul,</p>

<p>If you will renormalize the lepton mass then it all works out fine.</p>

[tom_mann1]

<p>Alan, you are assuming that virtual particle Feynman loop effects will fix the infinity of film grain posts. From sad experience, I can predict only more divergence.</p>

<p>;-)</p>

<p>Tom M</p>

[scott_ferris]

<p>You guys are just being silly now.</p>

<p>Besides, we all know the real question is when, if ever, digital 135 will ever rival film 135, because it is quite obvious from inline posts that even 24 MP 135 format cameras don't come close to achieving the image quality I can get with a 110 film camera with a plastic lens from the early 80's.</p>

<p>All in jest :-)</p>