But when I asked them to rescan the Portra 160 today, I was told that how much rebate shows is determined by "...... where the exposure falls within the edges of the film itself. Exposure can also cause issues with reading frame lines, underexposure, flares and light leaks can cause misalignment of the scans."
That sounds strange to me. I don't understand how exposure within the image would affect whether rebate shows in the scan.
It's somewhat offtopic, but I've been operating a Flextight for a few months now, and it consistently hits the alignment within fractions of a mm on the device I've been using, which is an old Precision II unit. Maybe the transport was changed in later versions? Initially I allowed for a fairly liberal border around e.g. a 35mm frame, but I'm now entirely comfortable drawing a very tight bounding box just around the aperture in the knowledge that I'll get precisely that crop in the final file. I was actually surprised at how well this works.You would be surprised how different the geometry of two scans of the same frame can be on this type of scanners (same goes for Flextights, for example).
I had always assumed the reason the rebate was uneven was a physical issue -- how the film was positioned when it went through the Noritsu. When rebate not even on all sides, I assumed they didn't (or couldn't) get it positioned perfectly.
If you would have the time to make two consecutive scans of the same frame and then make a gif toggling between those two scans, I would be very surprised if it showed no difference in registration. This “problem” is fairly well known*. But it may be limited to scanners that are not maintained well, though.
Note that the maximum shift between these 3 frames was around 4 pixels, or a 160um distance. Note also it's only along the longitudinal axis, which makes sense as that's pretty much the only one on which any shift can be produced due to longitudinal transport inconsistencies.
Sorry for the offtopic; insofar as we can derive something from this example, I think it boils down to "if possible, scan with a margin to account for virtually inevitable inconsistencies". I've not (yet) repeated the experiment with my Scan Dual IV, but I'm sure there will be a small inconsistency in that one as well, however small.
A further perhaps marginally relevant remark is if you scan the same negative on different scanners, you'll get files that won't perfectly overlap.
I offered a translation into real-world shift, which is around 160um. Of course this is visible, but as said, given a sufficiently large aperture, this could be allowed for. The problem is likely that the Noritsu doesn't easily offer this opportunity. IDK, I've never used one.It feels like more than 4px or is the scan resolution set very low so that 4px mean quite visible shift in frame content?
But a pretty good job color matching those scans!I donated my Microtek 4000tf and Canoscan FS4000US so I can't do further test between the two, but the last scans I did on them showed absolutely huge differences in geometry:
I offered a translation into real-world shift, which is around 160um.
Sorry, I should have been clear; I downsize the file for display here. The difference on the original 600dpi scan was 4px.I know. It's just that my math was different, I came to the difference of 1% (4px in 400px width) --> 0.35mm for a 35mm frame, so I wasn't sure whether your real-world number was a bit off or (more probably) my math was flawed
I hope you'll post those elsewhere as well; I'd like to see the scans. Btw, I get an 'access denied' on Drive when I try to open the links.(more interesting bit from about this scans is that they are form the new Orwo NC200/Opticolour 200 preproduction film; I'm sadly not a fan)
I hope you'll post those elsewhere as well; I'd like to see the scans. Btw, I get an 'access denied' on Drive when I try to open the links.
I don't think that's what they're saying, though. The way I read their quote is that they're saying two things:
1: The amount of rebate is influenced by where the exposure falls on the film. The gate and alignment on cameras is not always the same. Some cameras will expose a slightly larger frame, some expose a smaller frame. Some may be slightly offset to one edge of the film.
2: Frame recognition is influenced by exposure; e.g. a frame with one half of severe underexposure may not be correctly recognized and this will affect the scanner's choice of frame alignment. The result may be the rebate being wider or narrower (or lacking) on either side.
Perhaps @brbo can comment on this; I think he has done extensive work with Noritsu scanners.
I've yet to find a negative holder for any scanner that gives consistent borders, especially if using different cameras and lenses with wide angle lenses making a larger image on the negative than telephoto lenses. So with a film whizzing through the machine it has little control except to prioritise the image area. I'm sure if it had a brain the Noritsu scanner would think success was to make 36 scans all the same size without a border showing. Perhaps shorter six exposure lengths of film allow the lab to turn it 180 degrees and try scanning it rotated which can change where the border comes, and this is one thing you'd do at home if a border was important. Ultimately there are only three or shots on a film that are keepers if a good photographer is lucky, so nowadays adding a border with software is faster and more cost effective than paying for somebody to struggle and possibly fail.
Just fyi -- both rolls (the one with good rebate and other with bad rebate) were shot with same camera and lens.You have to consider they might have different scanners (each will show more or less rebate because tolerances will come in play), as mentioned different cameras will have different frame sizes, even lens with different focal lengths might have slightly different frame sizes exposed on film, orientation of the film when fed into scanner will matter, film transport in camera and in scanner.
But it mostly comes down to how the Noritsu scanners operate. Even if operator sets positioning per every single frame during the preview, those marks will never be hit exactly during scanning. Film transport in Noritsu scanners relies on rubber rollers in contact with the film. Any of the many rollers not perfectly round, grippy enough, etc. will cause that scanner won't be able to hit the mark set at the preview stage. You would be surprised how different the geometry of two scans of the same frame can be on this type of scanners (same goes for Flextights, for example).
I believe the lab has a special film carrier which allows for rebate to show, which is reason for the $7 charge to include rebate -- time to put different carrier in machine.And, as @250swb mentioned, the goal with those scanners was to avoid showing borders at any cost. You can get some additional frame estate from Noritsu raw files but that is some fuckery no lab will do for you even if you paid them $100 extra.
+1
Although I never operated a Noritsu scanner, I have done so on Frontier. While different equipment, they operate basically the same.
As has been mentioned, the native negative carrier was designed NOT to show any rebate. Custom made carriers can be ordered that will show the rebate on the negative. Also the software must be adjusted to show the negative image and the rebate area in the scan. While it involves a bit of investment in time and money on the lab's behalf, once set up, it should run smoothly (famous last words!!!)
I know that some 120 film cameras expose a slightly larger negative image area than others but it would only be 1 or 2 mm, I suspect, at the most.
I think the uneven rebate surrounding in the scans may be down to operator error. The negative is simply not positioned in the centre of the carrier.
When I operated Frontier 120 scanning, many moons ago, the negative carriers were all manual. The negative advance and positioning was manually adjusted by the operator.
I can understand the lab charging extra for including the rebate in the scan, besides in the initial carrier/software time investment, the positioning the image to show an even rebate would be more time consuming than normal scan.
Yeah, it's at least convenient to have the capability to do it yourself, and generally it's also more rewarding. And if you are in a position to invest sufficient effort into the whole thing, the end result can be better, too.
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