Scanning Black and White Film as Negative or Positive?

[brian steinberger]

I've begun archiving my best black and white negatives on my 9000 ED. I started scanning as "negatives", but gave scanning as a positive a shot for one negative and was amazed at the control I had in PS with a very flat scan to start. Highlights didn't get out of control as easily. Is this how I should be scanning my black and white negatives?

 

[glhs116]

It all comes down to taste and control. I am a colour shooter but I don't scan any negs as "negative" anymore. Just like sharpening at scan time, scanning in "negative" mode locks you in to the scanner software's way of doing it. Many people prefer to sharpen in post in a full-featured image application. I also now prefer the control I get from tools like ColorPerfect and negfix8 in conjunction with an image editor for inverting my negs. I can also revisit the scans later with different techniques or software without having to rescan.

Ultimately, it is up to you!

 

[pellicle]

Highlights didn't get out of control as easily. Is this how I should be scanning my black and white negatives?

personally I think so, but then my greatest interest in that method comes from the additional control one normally gets over the scanner driver software. You can work in a linear manner without applying curves this way, but few scanner software drivers allow that.

in my view ...: black and white neg scanning

this is epson software, but the concepts transfer to when I use nikonscan on my LS4000

 

[Alan Klein]

I don't understand how the scanner will do a better job one way or the other. The scanner doesn't know what type film it's looking at. It doesn't know or care if it's negative or positive. It's only measuring the light through celluate. Each scanner has a maximum DR that it allows it to see the data. The reversal or non reversal of that data has to take place after the scan. The analog sensor circuitry doesn't change. The scan can't change as far as I see. Unless you are actually changing the circuitry somehow but one would assume the manufacturer calibrated their circuits to get the most data from their machine. Any further adjustment to the hardware circuits, even assuming you have that ability, would only make the circuits less effective not more. Maybe I'm missing something, but that's how it seems to me.

 

[pellicle]

I don't understand how the scanner will do a better job one way or the other. ... Maybe I'm missing something, but that's how it seems to me.

you are missing that you get linear control and better fine tuning of black and white points WITHOUT introduced gamma issues when using slide that you can not access when scanning as negative.

 

[glhs116]

What you are missing is that the scanners are smarter than you think. Each piece of film is like a scene and is evaluated according to how dense it is and how bright the clearest parts are. The two big differences in how the scanner looks at film based upon you choosing "positive" or "negative" are:

* positive mode assumes the bright parts are highlights and tries to conserve them
* negative mode assumes they are shadows and sometimes clips them for a punchier result

* positive mode assumes the film is already colour balanced and scans all three colour channels at the same exposure
* negative mode knows that the exposure for each colour channel will be very different and attempts to set appropriate gain individually for each primary colour channel

Sam

 

[jeffreyg]

Do what works best with your equipment and software. Some scanning software programs let you choose the film and have multiple adjusting features. I like Sam's explanation and think it depends on the negative values as to which way to go.

HOME PAGE

 

[pellicle]

I agree, Sam's explanation was concise. To further my own I suggest you read this Alan
in my view ...: Negative film scans on Nikon Coolscans
although it's about Nikon it applies equally well to Epson or any other software for that matter

I also discuss that a little on this post where as I say " never send a machine to do a humans job ... the machine lacks sensitivity and experience"

 

[Alan Klein]

Everything described in those links only indicate that adjustments were done. Maybe I missed it, but I didn't see how those adjustments changed the data captured by the scanner itself. All adjustments seem to be done with the scanned data. While that can be done in the scanner with it's software, it can also be done in Post with other software such as Photoshop. It's kinda like a jpeg in the camera. You can set certain parameters (ie vivid, snow scene etc) but software changes the image in the camera after the raw data is captured by the camera sensor circuits. The only modification is when you change the ISO. Then the RAW data is different because the gain in the capture circuits amplifiers have been modified.

The only way I'm aware similar thing like ISO adjustment in scanner is when a scanner program scans slower and attempts to catch additional light in the shadow areas. Then the data actually captured is different although the results I've seen when present by tohers don't seem worth the effort. Now I'm not familiar with the Nikon scanner. So it's possible that its program somehow changes the gain of the amplifiers so the captured data can be different on separate scans. And thancombine them sort of like HDR programs. Other than that, the data captured would be fixed and can only be modified after the scan. Of course, the scanners software is set up to adjust the captured data with a few keyboard selections since it's part of a product. But using Photoshop, you should be able to get the same results although maybe not as intuitive as the scanner software.

I've been very interested in this issue because I've been trying to get better scans out of my V600 flat bed. I even contacted Epson but they never provided a straight answer other than Silverfast is pretty good. But then they package Silverfast with some of their scanners. So that's not exactly an unprejudiced endorsement. But I have found nowhere how anyone's software changes the captured signal during the scans including the above referenced articles.

 

[pellicle]

Everything described in those links only indicate that adjustments were done. Maybe I missed it

you did ... tell me, do you understand what setting black and white points means?

I'm serious, I would like you to give a brief explanation of what setting the black and white points on the scan means. Because you're above suggests you're thinking like exposure of camera while we're discussing scanning. Did you read the blog post I mentioned? Did you read the post above on black and white scanning? I mean read and understand?

 

[Alan Klein]

My full quote included the words in Italics: "Everything described in those links only indicate that adjustments were done. Maybe I missed it, but I didn't see how those adjustments changed the data captured by the scanner itself."

I stand by that. Setting Black and white points can be done in post. Doing it using the scanner software does not change the data that the scanner sensor reads. The DMax of the scanner is fixed.

Now, you can argue, and this may be where you're going, that setting the black and white points create an output in the image file that provides more data for the values that the scanner read. So that if the film has a range from let's say 15 -240 rather than 0-255, the 15-240 data output could be increased by moving the black and white points. So the output image file has finer data at the various points to work with once you get it over for post processing. Now there's an area I could agree with if that's what'. Is that how that works?

 

[glhs116]

Let me put it this way. You can take all scenes at the same exposure and then simply adjust the image in post. After all, this is the premise disposable film cameras are based upon. However, they have a very wide range sensor (the negative film) and no one expects miracles from them. There are no digital sensor fixed-exposure cameras for general use because digital sensors have a short range.

Here is the key: neither is your scanner a fixed-exposure device. It is also making do with a very limited range digital sensor and could never make a decent image of varied originals without varying it's exposure to be optimum for whatever is in front of it. Typically, each individual frame in a strip gets an individual exposure set.

There is no aperture adjustment in a scanner's optical system. Typically, the exposure is adjusted by adjusting the "dwell time". This is the amount of time the sensor array lingers over each row in the scan and is analogous to shutter speed. Since the scanner scans the three primary colours independently it can set different dwell times for each. This is something a camera cannot do.

Go ahead. Scan a darker denser frame followed by a brighter less dense frame. I'm referring here to the film itself and not the scene since, obviously, a dark night scene yields a thin negative but a dense slide. Time the two scans. The denser piece of film will take longer to scan.

Your misconception that all scanner exposures are identical and all adjustments are simply being done to a fixed-exposure capture is just that: a misconception.

 

[Aristophanes]

Scanning is, by definition, post processing.

 

[Alan Klein]

glhs116: Please provide a source for your statement that the "dwell time" varies and that scanners are "not fixed exposure" devices. How can the scanner know during the scan whether the spot it is looking at is darker or lighter and and since it has no idea what the scene was that the film represents at that point. It's the same thing with auto adjustment for exposure in cameras. If you try to shoot a snow scene, the camera will under exposure because it has no idea it's looking at snow. It's trying to adjust to gray. The scanner is just as dumb. It's just shooting a fixed light though cellulose and reading how much photons pass through. Since film only represents a few stops, it only has to measure from black to clear so the exposure can be "fixed". Which scanner are you referring too?

Would like to get some explanation how setting the black and white points effect the amount of data collected on film shots that are less than 0-255. If someone could clear that up for me, that would help explain how better data can be gotten during the scan.

 

[glhs116]

How can the scanner know during the scan whether the spot it is looking at is darker or lighter and and since it has no idea what the scene was that the film represents at that point.

Have you never noticed the little prescan the scanner does before the full scan?

Since film only represents a few stops, it only has to measure from black to clear so the exposure can be "fixed".

This is true for unilluminated film which is why film is never scanned without illumination. The brighter the illumination the more dynamic range will be presented to the sensor. The scanner manufacturer designs the scanner so that the brightness of the lamp and the range of the sensor are well matched. This is further refined by changing the dwell time for a given scan based on the maximum brightness determined in the prescan.

As I said, do the experiment. The results are obvious. I once scanned a deeply underexposed Velvia slide on my Coolscan and it took twenty minutes to scan the one frame. However, even my crappy consumer HP 4010 takes longer on denser material at the same settings.

 

[Alan Klein]

I don't have a Coolscan so I can't do your experiment. But I haven't noticed any change in scan speed between pictures on my Epson V600 flat bed except when I use ICE or when I change the bit selection. They are the same times when I've clicked auto adjust and when auto is shut off. What is interesting however is that when I do adjustments after the pre-scan scan but before the actual scan, the scanner applies the various settings I selected to show me what it looks like. Obviously, those are software adjustments since the main scan hasn't occurred yet. It seems to me that the same adjustments are done by the scanner software to the main scan. But no changes to the scanner's data capture process itself occurs.

Look, I could be wrong. But without an authoritative source for your statement that the "dwell time" varies and that scanners are "not fixed exposure" regarding the Coolscan or any other scanner, your points are only guesses as mine are. I've actually contacted Epson numerous times to try to get explanation of the scan process on their scanners. And they never have provided details.

 

[pellicle]

misread see later post

 

[pellicle]

Alan I'll try this again

Everything described in those links only indicate that adjustments were done. Maybe I missed it, but I didn't see how those adjustments changed the data captured by the scanner itself.

do you understand linearity of data? Please just re-read my post (it was quite short) and ask me what part you do not understand.

data will be altered because of the gamma (ask if you don't understand why)

but I don't mind, you seem to be bent on not grasping this and it is no skin off my nose either way

 

[pellicle]

Would like to get some explanation how setting the black and white points effect the amount of data collected on film shots that are less than 0-255. If someone could clear that up for me, that would help explain how better data can be gotten during the scan.

you GOT it in the previous posts but seem to be ignoring it or refusing to read the blog posts. As I said the negative setting will make different estimations of the black and white points, in the scan as positive YOU make those choices.

Further you can adjust better ... as previously posted.

 

[pellicle]

Allan, because I'm quite certain you did not read my blog post I will put it here to make it clearer

So, I've now set the "clipping points" on this ready for a scan. Take a look carefully at the numbers and the position of the sliders for black and white points.

Did you notice over on the black level that it would seem I've left a section where there seems to be no data? Well this is because I know that there is likely to be something there that the machine thinks is noise but I know is not. This is part of why I say never send a machine to do a humans job ... the machine lacks sensitivity and experience.

 

[Alan Klein]

Does changing the black and white points change the data collected? If so, how does it do that? What changes to the scanning process occur during the scan? Thanks Alan.

 

[glhs116]

I don't have a Coolscan so I can't do your experiment.

Also my Konica Minolta DiMage Dual IV, also my HP Scanjet 4010, also matching pelicle's experience with the Epsons.

What is interesting however is that when I do adjustments after the pre-scan scan but before the actual scan, the scanner applies the various settings I selected to show me what it looks like. Obviously, those are software adjustments since the main scan hasn't occurred yet. It seems to me that the same adjustments are done by the scanner software to the main scan.

Yes and no. In that order.

Sam

 

[artobest]

Alan, hi - my first post here. I think you're having trouble getting your answer, so I just want to say that, as far as I am aware, setting the black and white points in the scanner software is simply a software step (same as doing it in your image editor after the fact) and in no way affects the actual physical scan. This is one reason why it's important to scan in 16-bits, because otherwise you may end up with a picket-fence histogram, depending on the density of the original.

Hope that helps.

Peter

 

[Alan Klein]

Hi artobest. Welcome to the forums and thanks for your response. If the image can be scanned so that all data falls withint the 0-255 (no clipping at either end), would setting the black and white point before the scan create a better data file or the same?

 

[glhs116]

I just want to say that, as far as I am aware, setting the black and white points in the scanner software is simply a software step (same as doing it in your image editor after the fact) and in no way affects the actual physical scan.

Except that the only problem is that I have offered an experiment to prove that post adjustments are not the same and pellicle has actually graphed and documented the same thing:

in my view ...: Epson 3200 more optimal scans

I'm not sure there is anything to be said further that is not covered in the link above. Please read carefully.

I would suggest that you (and Alan) perform the same experiment yourselves. Change stuff and time it. I suppose it is possible that one of you have a scanner that is built differently. However, I have three scanners, one of which is a very cheap and nasty HP consumer flatbed. They all take longer to scan if you scan darker material.

Sam