Why do some scanners want the base side down? Epson 3170

[RLangham]

So when I got my Perfection 3170 back out after not using it for four years, I intuitively loaded the carrier emulsion side down the first time, because that’s what makes sense and I was aware that that’s how most flatbed scanners work.

The next time I loaded it, on the back half of the same roll of 35mm, I took heed of the symbol on the carrier, which shows you to load it so that the image is reversed when seen from that side (I.e., looking at the emulsion). I noticed a subjective improvement in contrast and possibly some improvement in sharpness, on all twelve frames compared to the first twelve.

So while that’s hardly enough evidence to be sure, it does suggest to me that it’s not arbitrary, like people on Reddit claim it is; the scanner is well and truly designed and programmed for scanning through the film base. It probably focuses like, .25mm further than most film scanners or something like that.

My question is, and I’m sorry if this is well-trod ground, is why would they design apparently multiple models of consumer scanner from Epson to work the opposite way of the conventional flatbed scanners? I know that the conventional wisdom is that scanning with the emulsion side down reduces the appearance of newton rings in the scan. And it also just makes sense that you would want to be scanning the emulsion directly and not through the base, which might be stained by certain developers or tinted amber in the case of color negative films.

Do any professional or newer higher end consumer scanners work this way?

 

[koraks]

In terms of focus or resolution - that can't be it, really. The depth of field of a typical flatbed scanner is relatively big and the thickness of the film is on the thin side to make much of a difference. Moreover, the film carriers are generally not designed with the kind of precision that would make the thickness of the film a significant factor; generally the film doesn't sit very flat to begin with, and/or there's a reasonable margin of error where the emulsion side ends up in relation to the lens.

I can think of reflections being a consideration. The emulsion side of the film is generally more shiny and pointing that side away from the light source might be beneficial. However, most Epson flatbeds work the exact other way around. On the other hand, that might be explained with the orientation of the image in mind (but you'd have to think it through; I admit I haven't, thoroughly). The obvious consequence of having the film upside down is that the image ends up being mirrored and the user will have to flip it to make the orientation come out correctly. Of course, this could only be a minor argument in the larger scheme of things as flipping the image is so mundane and easy to do.

For the most part, I've found this to be a total non-issue; I've scanned 'correctly' and upside down lots and lots with my Epson 4990 and I've never seen any sign of a difference in image quality either way.

scanning with the emulsion side down reduces the appearance of newton rings in the scan

Only if the film is in direct contact with the glass plate. I'm not aware of any desktop scanning system (apart from actual drum scanners, but even these use fluid mounting) that are designed to scan film as it's in direct contact with anything.

 

[RLangham]

In terms of focus or resolution - that can't be it, really. The depth of field of a typical flatbed scanner is relatively big and the thickness of the film is on the thin side to make much of a difference. Moreover, the film carriers are generally not designed with the kind of precision that would make the thickness of the film a significant factor; generally the film doesn't sit very flat to begin with, and/or there's a reasonable margin of error where the emulsion side ends up in relation to the lens.

I can think of reflections being a consideration. The emulsion side of the film is generally more shiny and pointing that side away from the light source might be beneficial. However, most Epson flatbeds work the exact other way around. On the other hand, that might be explained with the orientation of the image in mind (but you'd have to think it through; I admit I haven't, thoroughly). The obvious consequence of having the film upside down is that the image ends up being mirrored and the user will have to flip it to make the orientation come out correctly. Of course, this could only be a minor argument in the larger scheme of things as flipping the image is so mundane and easy to do.

For the most part, I've found this to be a total non-issue; I've scanned 'correctly' and upside down lots and lots with my Epson 4990 and I've never seen any sign of a difference in image quality either way.


Only if the film is in direct contact with the glass plate. I'm not aware of any desktop scanning system (apart from actual drum scanners, but even these use fluid mounting) that are designed to scan film as it's in direct contact with anything.

Huh. Very strange then. Perhaps the cupping of the film is the main concern, but it seems like it would be a problem in either direction. It’s also trivially easy for the scanner to flip the image internally as it’s compiled so there’s no reason to think that should have been an actual design concern.

Do you think a 4990 is worth getting in 2026 or should my upgrade be to something a little newer?

 

[koraks]

I agree it's puzzling; I think ultimately it boils down to pretty much a random decision, really. I've never been able to find a compelling argument for either position.

Do you think a 4990 is worth getting in 2026 or should my upgrade be to something a little newer?

Depends on your requirements; in particular what film sizes you digitize. If you're working with sheet film, the 4990 is convenient as it can scan up to 8x10" negatives in a single pass with more than decent resolution. If you mostly/only use 35mm and medium format, you can get at least as good or better quality (depending on specifics) with a camera scanning setup - and also with dedicated film scanners, but those tend to be more rare and/or more costly. It also depends on whether you may happen to have access to an available 4990 that's for sale/grabs attractively. In short - it depends! Having said that, within the flatbed scanner arena, it's a competent performer.

 

[Michael Howard]

If you use the Better Scanning holders with the AN glass inserts, you pretty much have to scan emulsion down and reverse the image in post, as the AN glass sits on the base side to flatten the negative out. As Korak's said, it makes no difference other than you get sharper scans (marginally) with the flatter negatives. This was true for my old 3170, and the V600 I currently have.

 

[Chan Tran]

It's mainly where the light source and the sensor are located at.

 

[koraks]

It's mainly where the light source and the sensor are located at.

Are the flatbed scanners very different in this regard? I thought the default architectural feature that they all share is a light source in the lid and the sensor in the base of the machine.

 

[RLangham]

Depends on your requirements; in particular what film sizes you digitize. If you're working with sheet film, the 4990 is convenient as it can scan up to 8x10" negatives in a single pass with more than decent resolution. If you mostly/only use 35mm and medium format, you can get at least as good or better quality (depending on specifics) with a camera scanning setup - and also with dedicated film scanners, but those tend to be more rare and/or more costly. It also depends on whether you may happen to have access to an available 4990 that's for sale/grabs attractively. In short - it depends! Having said that, within the flatbed scanner arena, it's a competent performer.

Well, inability to scan 4x5 is one of my motives for upgrading. So 4990 may be one candidate. I’m sure there are other comparable ones. Most of the ones I see at thrift stores are older or lesser in specs even than the 3170, and getting a scanner on the bay is risky risky… sure I’d love a dedicated film scanner, but idk that I can justify one.

When my first 3170 broke, I went with the devil I knew, since the only other film capable flatbed I’d tried was newer but had much worse software, much worse film carriers and wasn’t capable of medium format or slides. Sometimes now I wish I’d done more research at the time and gotten something newer.

Looks like the 4990 can take the same film holders?

As for camera scanning… that always seemed more expensive to me, since a good DSLR with the resolution I would want, plus a good prime lens, is already probably more than a 20 year old flatbed scanner that achieves the same resolution, and that’s assuming I can competently build the scanning jig for it myself. But then again I’ve never bought or been that interested in buying a DSLR up to now, so maybe the used prices are way lower than I think. And I suppose nowadays you can substitute “mirrorless” for “DSLR”.

It's mainly where the light source and the sensor are located at.

I don’t think so? Some or even most (non-Epson) flatbeds instruct you to scan emulsion down towards the sensor.

 

[Franswa]

Yes it is a mystery; my v800 says emulsion side down, while my 10000XL says emulsion side up.

 

[Alan Edward Klein]

How does the scanner's software handle the image after the scan? In other words, do you have to reverse the image after the scan to get it to show correctly left to right? If you do, then you scanned it upside down. So it could be that's how this particular scanner's software works. Nothing to do with hardware issue mentioned.

 

[djdister]

Yes it is a mystery; my v800 says emulsion side down, while my 10000XL says emulsion side up.

Not accurate. The V800 says to load the film holder with the emulsion side down, then flip the film holder over so that you are scanning with the emulsion side up. Whereas the film holders in the V750 do not have the "flip 'em over" step, and so you just load them with the emulsion side up to scan.

From the V800 manual, a two step process:

 

[RLangham]

How does the scanner's software handle the image after the scan? In other words, do you have to reverse the image after the scan to get it to show correctly left to right? If you do, then you scanned it upside down. So it could be that's how this particular scanner's software works. Nothing to do with hardware issue mentioned.

As I said, scanning it emulsion up is correct on the 3170, as indicated on the carriers, and you do not have to flip the image when scanning it that way. I only did it the other way completely by accident.

I’m just trying to understand why some Epson scanners are this way while probably a majority are the opposite? It doesn’t have to do with reversing the image internally, since that’s a trivial concern in the software. Ones that are made to scan emulsion side up would compile the image line by line in one direction, and ones that scan emulsion side down would do the same thing in the opposite direction. They just do it according to the way they’re designed to be loaded… and the question is why some are designed one way and some the other.

And as I say, I felt that the contrast was better in the images scanned the way the scanner recommends, versus the ones that I accidentally reversed, so I felt there was some technical difference. But it’s not conclusive, since obviously that was half of one roll of film that I shot without a meter, and it could be that I was underexposing in certain light conditions and not others.

 

[Franswa]

Not accurate. The V800 says to load the film holder with the emulsion side down, then flip the film holder over so that you are scanning with the emulsion side up. Whereas the film holders in the V750 do not have the "flip 'em over" step, and so you just load them with the emulsion side up to scan.

From the V800 manual, a two step process:
View attachment 424554 View attachment 424555

Ah thanks for pointing that out. I should have been more clear in that I am not using the OEM film holders but rather the BetterScanning variable height mount and it's with this holder that the emulsion side is facing down.

 

[MattKing]

I’m just trying to understand why some Epson scanners are this way while probably a majority are the opposite?

Some were probably designed by the team used to designing the document and print photo scanners, who then added the film scanning capacity as an afterthought.
While others were designed by the film scanning team, who included the document and print scanning capacity grudgingly.

 

[RLangham]

Some were probably designed by the team used to designing the document and print photo scanners, who then added the film scanning capacity as an afterthought.
While others were designed by the film scanning team, who included the document and print scanning capacity grudgingly.

That makes sense!

 

[koraks]

Looks like the 4990 can take the same film holders?

I'm not sure, but the 4990 is pretty flexible and will scan pretty much whatever, provided it fits within the window area that the 8x10" transparency mode supports, and the initial calibration strip on the glass is left bare. If the holders you've got can accommodate those requirements, it'll work.

Btw, don't tell anyone, but I mostly just smack 4x5" negs straight onto the glass and call it good. However, optimal focus is a bit above the platen, so for the absolute best results you may want to raise the negative by ca. 1.5mm to get it in the plane of sharp focus. The stock holder that came with the 4990 Pro (or whatever the package was called that included these holders) works very well for this, but doesn't allow for scanning all the way up to the edge of the film.

 

[RLangham]

I'm not sure, but the 4990 is pretty flexible and will scan pretty much whatever, provided it fits within the window area that the 8x10" transparency mode supports, and the initial calibration strip on the glass is left bare. If the holders you've got can accommodate those requirements, it'll work.

Yes, the 3170 holders seem to have the same cutout for the calibration strip as the 4990 carriers, so I’m betting they’ll work. That may make it easier to get a deal on the scanner, if I can accept one that doesn’t have all the carriers.

Btw, don't tell anyone, but I mostly just smack 4x5" negs straight onto the glass and call it good. However, optimal focus is a bit above the platen, so for the absolute best results you may want to raise the negative by ca. 1.5mm to get it in the plane of sharp focus. The stock holder that came with the 4990 Pro (or whatever the package was called that included these holders) works very well for this, but doesn't allow for scanning all the way up to the edge of the film.

My 4x5 negatives have the border from old wooden film holders anyways.

I tried what you describe on the 3170 and at least with the Epson Scan software it didn’t seem to do very well.

 

[koraks]

You mean you tried scanning straight on the glass? When I do this, I need to set the option "use film area guide" instead of the "film holder"setting. However, I don't know if the 1370 ever supported that alternative; I don't know that particular scanner.

 

[RLangham]

You mean you tried scanning straight on the glass? When I do this, I need to set the option "use film area guide" instead of the "film holder"setting. However, I don't know if the 1370 ever supported that alternative; I don't know that particular scanner.

I don’t believe it does, I think film holder is assumed on that model.

 

[Alan Edward Klein]

I'm not sure, but the 4990 is pretty flexible and will scan pretty much whatever, provided it fits within the window area that the 8x10" transparency mode supports, and the initial calibration strip on the glass is left bare. If the holders you've got can accommodate those requirements, it'll work.

Btw, don't tell anyone, but I mostly just smack 4x5" negs straight onto the glass and call it good. However, optimal focus is a bit above the platen, so for the absolute best results you may want to raise the negative by ca. 1.5mm to get it in the plane of sharp focus. The stock holder that came with the 4990 Pro (or whatever the package was called that included these holders) works very well for this, but doesn't allow for scanning all the way up to the edge of the film.

The V850 film holders have adjustments with .5mm incremental indents running from 2.5mm to 4.5mm, with 3.0 being the factory design nominal setting. When I got my V850, I found that it made a big difference in where you set it. So, not keeping the film 3.0mm will give more unfocused results unless you're not using the holders and place the film directly on the glass platen. Then the secondary lens is used with restricted focusing, but focused on the platen as it would if you were copying prints.

 

[RLangham]

I don’t believe it does, I think film holder is assumed on that model.

Yes, it doesn't give the option. Presumably Vuescan might allow it, but Epson Scan doesn't for this model.