Film vs Digital - Color Rendition

<blockquote>

<p>Norman Koren (author of imatest) measured 103 lp/mm @ MTF10 using Velvia with a 8000 dpi scanner and sharpening. And only 64 lp/mm without sharpening.</p>

</blockquote>

<p>He didn't measure it. He got it by simulating it - i.e., by plotting it on a chart. He also got around 68 lp/m for Velvia+lens, before scanning, using the same method. I don't understand how that can increase to 103 lp/mm after scanning.</p>

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<p>The 103 lp/mm figure is after sharpening.</p>

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<p>It is after<em> scanning and</em> sharpening.</p>

"It is after scanning and sharpening."

LOL how else do you sharpen?

-Cheeky New Generation

;)

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<p>It seems that sharpening with film is important for maximum high frequency detail while with digital sharpening has only minimal effect on high frequency detail.</p>

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<p>No, that's not the case. Sharpening is equally important for digitally originated images. Most current digital imagers are fronted with a Bayer filter. As with all physical devices it is necessarily imperfect. </p>

<p>In this case, the filter starts to suppress lower frequency image detail well before the designed cutoff frequency. The manifestation on print is lowered contrast for high frequency image detail - exactly like film, just postponed.</p>

<p>Sharpening a digital image compensates for the Bayer filter losses. It noticeably extends the regime through which contrast would would have started to droop. In principle, aim for 100% MTF response all the way to the Nyquist limit. You can't get there of course, but it's possible to come quite close.</p>

<p>By the way, it seems that digital camera users often pine for less dense imagers. There is some merit to this in terms of potentially better noise performance. However, the flip side is that a dense enough imager can probably forgo the anti-aliasing filter altogether. Go dense enough, and imperfections in the lens itself inherently serves as the AA filter.</p>

<blockquote>how else do you sharpen?</blockquote>

<p>My point was that before scanning the resolution was 68 lp/mm. After scanning it came down to 64 lp/mm, which is understandable. Then sharpening raised it to 103 lp/mm! Some contrast that has been attenuated on film can be recovered by sharpening but I have a hard time wrapping my head around an increase from 64 lp/mm to 103 lp/mm.</p>

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<p>I have a hard time wrapping my head around an increase from 64 lp/mm to 103 lp/mm.</p>

</blockquote>

<p>I don't know if it makes any difference but a 8000 dpi scanner have a theoretical maximum resolution of 166 lp/mm. So maybe a lot of low contrast high frequency detail has been captured and with some aggressive sharpening that's enough to bump it up to MTF10.</p>

<p>BTW, I didn't get that all values on Norman Karens site was simulated. Sorry about that.</p>

<blockquote>

<p>No, that's not the case. Sharpening is equally important for digitally originated images. Most current digital imagers are fronted with a Bayer filter. As with all physical devices it is necessarily imperfect.<br>

In this case, the filter starts to suppress lower frequency image detail well before the designed cutoff frequency. The manifestation on print is lowered contrast for high frequency image detail - exactly like film, just postponed.</p>

</blockquote>

<p>I'm not sure. I was just looking at the MTF charts from Erwin Puts' and high frequency detail with a low MTF didn't respond to sharpening. I guess it also depends on how the sharpening was applied.</p>

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<p><strong>Dave</strong>: My math isn't wrong (1/Rsystem = 1/Rlens + 1/Rmedium is well established). And I'm not trying to tell anyone anything. I'm just pointing out that if you use this formula, you get a ridiculous resolution requirement for the lens. Hence what I was trying to say was that <em>something was wrong </em>with our calculations or our interpretation. I.e. at the onset I <strong><em>agreed</em></strong> with you that it seemed ridiculous to require a lens capable of resolving 2400 lines/mm to get the resolving power of Velvia we calculated from Mauro's experiments. You're not contributing to the discussion by just repeating 'you don't need a 2400 lines/mm resolving lens to get 150 lines/mm on Velvia film'. The other guys here who posted after you are actually helping by offering a reason for why my calculation might be off...<br /> Cheers,<br /> Rishi</p>

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<p>Actually Rishi, the topic is film vs digital - Color rendition. Your bringing up resolution targets is off topic and thus it YOU who really isn't contributing. And unless I'm mistaken, you're not a moderator here nor the OP, so keep your opinions of who should be posting and who shouldn't to yourself....I don't need to follow your instructions thank you very much! And if you had a basic understanding of how the formula works and what you feed it, you wouldn't require a ridiculous figure for the lens.</p>

<p>Dave, once again you appear to over-interpret what I write. I expressed no such opinion on whether or not you should be posting; instead, I pointed out to you that you simply repeating one line or making statements without proffering any further explanation doesn't help this discussion, & that if you wanted to actually contribute, you could follow the examples of the guys after you who hashed out exactly what was going on. It was an encouragement for you to further explain your stance. Perhaps you should take things a little less personally.</p>

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<p>Your bringing up resolution targets is off topic and thus it YOU who really isn't contributing.</p>

</blockquote>

<p>... And if that's how the world worked, knowledge would be stagnant.</p>

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<p>And if you had a basic understanding of how the formula works and what you feed it, you wouldn't require a ridiculous figure for the lens.</p>

</blockquote>

<p>That's what <strong>I've</strong> been saying from the very beginning. And yet the math spoke for itself. Your response "Did you mean to type 2400 or 240?" indicates to me that you weren't even attempting the math; just quoting numbers from other people's tests. So I'm not sure why you call out my understanding of a simple formula. My formula & math were fine; it was our interpretation of Fuji's reported numbers that was off.</p>

<p>Did you even bother to read my post that you quoted (where I pointed out I've been agreeing with you all along that you shouldn't need a lens of such ridiculous resolving power) or all of the subsequent discussion? Should I start repeating myself in order for you to actually read what I write?</p>

<p><em>First, film (or scanners) do not interpolate color and this translates into higher color resolution which provides a less smoothened (infamously "plasticy") rendition.</em></p>

<p>This is simply not true Mauro. See attached. Note that the 7D has finer resolution of relief texture details, which are color, than 35mm Velvia 50 on an Imacon scanner.</p>

<p>"Plastic" is a complaint that comes up when too much NR is used on high ISO images or when large prints are made from lower resolution files. It is not the result of Bayer interpolation.</p><div>[ATTACH=full]544101[/ATTACH]</div>

I’ve hit upon this side by side comparison image numerous times now researching related topics and I thought I’d leave a comment for posterity, since Google thinks it is so important.

Although as a comparison it’s lacking and there is a whole host of unknowns, it’s still uncanny how the original poster was so blinded by the “everything digital is good” religion that he/she overlooked how blatantly much better and correct the film photo is.

In fact the image can used as a good showcase of the exact opposite that it was made to illustrate.

Look at the colour details for instance. In several places coloured lines are either missing or converted to black by the demosaicing. The lake in the upper right quadrant has black lines taken out altogether for some reason.

These are just small immediately visible symptoms of a swath of not so eminently visible faults and artifacts occurring in all digital images. Artifacts impacting image quality subtly but fundamentally, and not just in isolated details that you can easily point out.

Also look at the stars in circles. At first they might appear sharper on the digital photo, but notice how they are actually real star shapes in the film image but has invented detail in the digital photo.

While at a superficial glance the digital image might look sharper and higher contrast it really holds much less data and more importantly is less pleasant to look at in enlargement. Which is after all, much of the point of resolution: To be able to print large and still have a pleasant to look at image.

I know the digital image is only eighteen megapixels and the current standard seems to hover around twenty four for sensible sensors, but I think the observations still more than holds up, since:

A. Scanning methods have progressed equally. Macro photography of film has overtaken anything that the already ailing dedicated scanners of 2011 could muster, not to speak of the gold standard of wet printing.

B. The film type used was probably chosen on the erounous assumption that slide was the best showcase for all that is good and great about film, which is of course not true. C41 has for one undeniably higher resolution, no matter which way you look at it.

It’s analogous to the (overused I know, but still relevant) Pepsi Challenge findings, with Coca-Cola vs. Pepsi in large contra small beverage containers.

Some sensory stimulus plays on aspects of our sensory apparatus that “has bad taste” so to speak. We soon tire of and see through those “cheap tricks” with more exposure though. Trouble is in the global market place, bad taste often wins because you only have a short time of exposure and judgement before purchase, and there’s is always a fresh supply of naive people.

PS. I don’t want to hear any malarky about bringing this thread “back from the dead”. Because, that is exactly what forums and the text on the internet as such, is good for in general. IE searching through and getting to content freely at any time seconds or decades after they took place:

This thread was ridiculous nearly 8 years ago, and it's even more ridiculous now, since many of the images have disappeared from it.

I’ve hit upon this side by side comparison image numerous times now...

- What side-by-side comparison image would that be? Give us a clue what on earth you're talking about, and why you've resurrected this thread.

PS. I don’t want to hear any malarky about bringing this thread “back from the dead”.

- Well you're going to if you don't make any cogent point in the process.

This thread was severely lacking illustration in support of many of its assertions in 2011. Adding more words with no supporting images does nothing to strengthen or undermine any of the arguments previously put forward.

So what's your point; and what visual evidence can you supply in support of it?

I don't know where this came from but ...

With three non-negative values, you can represent colors in a triangle on the CIE color diagram.

Less than perfect sensitizing dyes, dye-cloud dyes, Bayer filter dyes, or scanner filters will reduce the available color space.

In some cases, you can do a linear transformation (matrix) to compensate for such imperfections.

Mostly, you can do that if the spectrum is accurately known.

Scanners should do this if they have the information, or approximate it if not.

First, film (or scanners) do not interpolate color and this translates into higher color resolution.....

- Can I quickly put this old lame duck out if its misery?

Here's a photomicrograph of the dye clouds in a typical

100 ISO colour film at a mid-density.

To give an idea of scale; the smallest individual specks of colour are between 2 to 3 microns across. The clusters or chains of dye-clouds are on average about 10 microns or greater.

Now a 24 megapixel APS-C digital camera has a 'pixel' pitch of 4 microns, but we have to multiply that by 1.5 to put things on an equal footing with a 35mm film frame. That gives us an area of 6 microns square, which would enclose an easily countable number of dye clouds from the above sample. Maybe 10 to 12? That gives us a possible 10 or 12 levels each, of Cyan, Yellow and Magenta dye density.

So the number of possible colours in a 6x6 micron patch of that film would be (12x12x12) = 1728. And I think you'll agree that's being generous looking at the above.

The same, scaled down, 4x4 micron area of our digital sensor can represent (255x255x255) = 16581375 colours. Or over 9000 times as many shades of colour than the film, for a similar subject area.

That's a massive, massive difference. I could be out by two orders of magnitude in my estimate of film's colour-representing ability, and it would still lag well behind the poorest 8 bit/channel colour capacity of a digital sensor.

But wait! Any digital camera capable of RAW capture can hold 12 or 14 bits/channel of colour refinement. So make that a factor of 16 or 64 times greater still per channel in favour of the digital sensor.

That's a mind-boggling margin to lose by, and a pretty indisputable differential to explain away with any degree of credibility.

Don't give me anything about "zombie threads".

This is exactly what the internet and in this case online forums are good for. Sharing information across time and space.

WTF would or should I start a new thread when I can add to, find support in and add to posterity by posting in an old one?!

This is a thread that comes up often in searches of various kinds, and other people will find it in the future.

This is the picture I was referring to:

Try quoting my monoblock of a post above to get a more readable format. I don't know why the forumware does that?

I’ve hit upon this side by side comparison image numerous times now researching related topics and I thought I’d leave a comment for posterity, since Google thinks it is so important.

 

Although as a comparison it’s lacking and there is a whole host of unknowns, it’s still uncanny how the original poster was so blinded by the “everything digital is good” religion that he/she overlooked how blatantly much better and correct the film photo is.

In fact the image can used as a good showcase of the exact opposite that it was made to illustrate.

 

Look at the colour details for instance. In several places coloured lines are either missing or converted to black by the demosaicing. The lake in the upper right quadrant has black lines taken out altogether for some reason.

These are just small immediately visible symptoms of a swath of not so eminently visible faults and artifacts occurring in all digital images. Artifacts impacting image quality subtly but fundamentally, and not just in isolated details that you can easily point out.

 

Also look at the stars in circles. At first they might appear sharper on the digital photo, but notice how they are actually real star shapes in the film image but has invented detail in the digital photo.

 

While at a superficial glance the digital image might look sharper and higher contrast it really holds much less data and more importantly is less pleasant to look at in enlargement. Which is after all, much of the point of resolution: To be able to print large and still have a pleasant to look at image.

 

I know the digital image is only eighteen megapixels and the current standard seems to hover around twenty four for sensible sensors, but I think the observations still more than holds up, since:

A. Scanning methods have progressed equally. Macro photography of film has overtaken anything that the already ailing dedicated scanners of 2011 could muster, not to speak of the gold standard of wet printing.

B. The film type used was probably chosen on the erounous assumption that slide was the best showcase for all that is good and great about film, which is of course not true. C41 has for one undeniably higher resolution, no matter which way you look at it.

 

It’s analogous to the (overused I know, but still relevant) Pepsi Challenge findings, with Coca-Cola vs. Pepsi in large contra small beverage containers.

Some sensory stimulus plays on aspects of our sensory apparatus that “has bad taste” so to speak. We soon tire of and see through those “cheap tricks” with more exposure though. Trouble is in the global market place, bad taste often wins because you only have a short time of exposure and judgement before purchase, and there’s is always a fresh supply of naive people.

 

PS. I don’t want to hear any malarky about bringing this thread “back from the dead”. Because, that is exactly what forums and the text on the internet as such, is good for in general. IE searching through and getting to content freely at any time seconds or decades after they took place:

- Can I quickly put this old lame duck out if its misery?

 

Here's a photomicrograph of the dye clouds in a typical

100 ISO colour film at a mid-density.

[ATTACH=full]1277179[/ATTACH]

To give an idea of scale; the smallest individual specks of colour are between 2 to 3 microns across. The clusters or chains of dye-clouds are on average about 10 microns or greater.

 

Now a 24 megapixel APS-C digital camera has a 'pixel' pitch of 4 microns, but we have to multiply that by 1.5 to put things on an equal footing with a 35mm film frame. That gives us an area of 6 microns square, which would enclose an easily countable number of dye clouds from the above sample. Maybe 10 to 12? That gives us a possible 10 or 12 levels each, of Cyan, Yellow and Magenta dye density.

 

So the number of possible colours in a 6x6 micron patch of that film would be (12x12x12) = 1728. And I think you'll agree that's being generous looking at the above.

 

The same, scaled down, 4x4 micron area of our digital sensor can represent (255x255x255) = 16581375 colours. Or over 9000 times as many shades of colour than the film, for a similar subject area.

 

That's a massive, massive difference. I could be out by two orders of magnitude in my estimate of film's colour-representing ability, and it would still lag well behind the poorest 8 bit/channel colour capacity of a digital sensor.

 

But wait! Any digital camera capable of RAW capture can hold 12 or 14 bits/channel of colour refinement. So make that a factor of 16 or 64 times greater still per channel in favour of the digital sensor.

 

That's a mind-boggling margin to lose by, and a pretty indisputable differential to explain away with any degree of credibility.

Do you think you had luck in convincing anyone the last time you used that image (reverse image Google)?

You pull most of your numbers and assumptions out of thin air, while others are irrelevant.

One only has to look comparisons of real images to see that even if the scanner is not of the highest resolution, film wins most of the time WRT colour resolution and depth. There is the famous example of red berries on a bush, that is there on film but is lost between the gaps in the Bayer array.

You forget/neglect to mention that those 14 bits bit per channel are sampled from an analog sensor, with all the problems associated with that.

If there is much advantage to that kind of resolution, it will mostly be in avoiding beating and interference, both when sampling the analog signal and when doing various kinds og post processing, including basic demosaicing.

A full range of 14, 12 and I doubt even sometimes even 8 bit, is not present in the original signal.

Separation of colours with the dyes used in the sensors bayer array, is problematic too of course.

Film is not binary in any kind of way. There is naturally noise introduced in the signal by the grain of the emulsion, but there is no levels or quantification as such.

Film is not binary in any kind of way.

- Of course it is. Learn something about photo-chemistry and then come back.

It's not me that's pulling figures and assumptions out of thin air, but you. Simply refuting facts is no argument, but I guess facts don't stand in the way of blind belief.

BTW, that picture of a map only reproduces the 4 CMYK ink colours used to produce the original map, and nowhere near enough shades of colour to prove or disprove anything.

- Of course it is. Learn something about photo-chemistry and then come back.

 

It's not me that's pulling figures and assumptions out of thin air, but you. Simply refuting facts is no argument, but I guess facts don't stand in the way of blind belief.

 

BTW, that picture of a map only reproduces the 4 CMYK ink colours used to produce the original map, and nowhere near enough shades of colour to prove or disprove anything.

I know more about it than you assume. Tell me where and in what way is film photography, or the processing of it binary?

Simply dishing out numbers is not an argument either. There are few facts in your estimate above.

Regarding the map example. It is of course not an ideal test subject, but it is telling and ironic that is was used as a proof of digital superiority, while glaringly showing off the problems.

The missing colours are plain to see, but notice how the sharpness even in black elements is estimated/guessed. The stars are in fact distinguishable as stars on film albeit at lower contrast, while the digital version is just weird blobs.

Regarding the map example. It is of course not an ideal test subject, but it is telling and ironic that is was used as a proof of digital superiority, while glaringly showing off the problems.

- Please post a link to where that map image can be found. There's insufficient information to make any judgement as to colour accuracy.

To do that, we'd need the actual map in front of us.

The missing colours are plain to see

- Only if we have some reference.

Tell me where and in what way is film photography, or the processing of it binary?

- In the case of a B&W emulsion, halide crystals are either reduced to opaque silver during development, or they're not. There's no shade of grey involved at all. The image consists of tiny specks of black silver on a near transparent ground. It truly is 'black and white' and quantised as such. On a microscopic scale there are no shades of grey to be found. I don't think you can get more binary than that!

The situation is similar for a colour emulsion, whereby tiny droplets of colour coupler are bound in an oily solvent and distributed throughout the gelatine carrier. Each droplet tends to be converted to dye, or not, in the presence or absence of developer oxidisation products.

Furthermore the 3 colour forming layers have a finite thickness, and can only hold a few dye cloud droplets within the depth of each layer. So in cross-section, you have those few dye clouds stacked to form a limited number of quantised levels of dye density. Not quite as binary as the B&W emulsion, but very limited in the number of levels of colour density that can be contained in a given area of film.

Can I ask if you have over 40 years experience of using film, and in some very technically demanding applications? Because I have. And such experience has given me a very good knowledge of film's strengths, weaknesses, and the processes involved.

Have you also examined film under a powerful microscope? I doubt it. Otherwise you wouldn't be making unfounded claims about its lack of quantisation.

-

 

(snip)

 

- In the case of a B&W emulsion, halide crystals are either reduced to opaque silver during development, or they're not. There's no shade of grey involved at all. The image consists of tiny specks of black silver on a near transparent ground. It truly is 'black and white' and quantised as such. On a microscopic scale there are no shades of grey to be found. I don't think you can get more binary than that!

 

(snip)

If all grains are the same size, then that is close to true. The result is a high contrast film.

But more usual, there is a range of grain sizes, where large ones are most likely to get enough photons to be developable.

The optical density increases as more grains develop in a given area.

With appropriate grain size range, a nice long straight (or close to straight) region on the characteristic curve,

results in the more usual contrast needed for usual lighting situations.

- Please post a link to where that map image can be found. There's insufficient information to make any judgement as to colour accuracy.

To do that, we'd need the actual map in front of us.

 

 

 

- Only if we have some reference.

I don't get it. Are you answering your own question?

It's quite simple, some colours and features are doing a disappearing act from the film to the digital picture.

No known film artefacts can produce large features or anomalies like that.

- In the case of a B&W emulsion, halide crystals are either reduced to opaque silver during development, or they're not. There's no shade of grey involved at all. The image consists of tiny specks of black silver on a near transparent ground. It truly is 'black and white' and quantised as such. On a microscopic scale there are no shades of grey to be found. I don't think you can get more binary than that!

 

The situation is similar for a colour emulsion, whereby tiny droplets of colour coupler are bound in an oily solvent and distributed throughout the gelatine carrier. Each droplet tends to be converted to dye, or not, in the presence or absence of developer oxidisation products.

 

Furthermore the 3 colour forming layers have a finite thickness, and can only hold a few dye cloud droplets within the depth of each layer. So in cross-section, you have those few dye clouds stacked to form a limited number of quantised levels of dye density. Not quite as binary as the B&W emulsion, but very limited in the number of levels of colour density that can be contained in a given area of film.

The spongy structures AgX develops into are obviously there or not, but their extent is not equivalent to the original size of the crystal automatically. That is governed by the amount of exposure and development centers.

Also as mentioned, by Glen there is various amounts of overlap and size of the crystals to take into account.

As a starting point for extended reading and discussion I can recommend Tadaaki Tanis two excellent books.

Can I ask if you have over 40 years experience of using film, and in some very technically demanding applications? Because I have. And such experience has given me a very good knowledge of film's strengths, weaknesses, and the processes involved.

Anyone can proclaim themselves as anything on forums. Also, you can easily be in a vocation for a lifetime without ever knowing more than what you need to know. You can easily get wrong mental models that persist because they "work" or are not an inconvenience.

I know university professors who think they are general experts in their field, but only really are reliable in their own specialty or vice versa.

Have you also examined film under a powerful microscope? I doubt it. Otherwise you wouldn't be making unfounded claims about its lack of quantisation.

Indeed I have, and also images of such are readily availible to googlers too.

It's quite simple, some colours and features are doing a disappearing act from the film to the digital picture.

No known film artefacts can produce large features or anomalies like that.

- We don't know that for certain, since we don't have access to how those pictures of a map, or maps were taken. Without visual sight of the original, everything you're stating as fact is just assumption and guesswork. And it's just one example that you're refusing to give us a link to the source of.

There are thousands more examples online that clearly show the superiority of detail and colour rendering of digital, for a comparable sensor/film area. Such as here, and posted by a film user, but not a totally biased one.

Yours is the unscientific and biased approach, by refusing to look at evidence other than one single amateurish example that's apparently undocumented in its methodology.

A full range of 14, 12 and I doubt even sometimes even 8 bit, is not present in the original signal.

- Another example of unsupported nonsense. Have a look at DXO labs analysis of digital sensor colour depth.

If all grains are the same size, then that is close to true. The result is a high contrast film.

- It doesn't matter about grain size. The point is that reduced silver is opaque, and that dye clouds are fairly uniform in size and density.

What is seen in film is a dithering of opaque or coloured specks that only give the illusion of continuous tone.

It's exactly analogous to the half-tone printing method, whereby various sized dots of a single-colour ink give the same illusion. But the colour depth or refinement is limited by the smallest sized dot that can be produced.

With appropriate grain size range, a nice long straight (or close to straight) region on the characteristic curve,

results in the more usual contrast needed for usual lighting situations.

- That has absolutely nothing to do with anything being discussed here. And as has been shown in another recent thread, what appears to be a straight line on a log/log scale is actually far from it.