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Epson Perfection V600 Scanner Inconsistency Question

 
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Posted 08/22/2019   11:36 am  Show Profile Check rlsny's eBay Listings Bookmark this topic Add rlsny to your friends list Get a Link to this Message
I recently noticed a huge difference between scanning a page full of stamps vs scanning just one stamp.

The first scan was cropped out of a full page scan. The second one was the result of just scanning a small area of the page. The page itself was the same, all other settings were the same.

I'm finding this rather disturbing. Do I have to scan each stamp individually to get that brighter appearance? Any suggestions?

(If this is the wrong forum, apologies)


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Posted 08/22/2019   12:41 pm  Show Profile Bookmark this reply Add Germania to your friends list  Get a Link to this Reply
What kind of background are using, black or another color? If black, does it cover the entire scanner area or just the stamp and some small amount of area around the stamp?

The underside of the scanner is white; if most of that is uncovered the exposure may be getting adjusted to provide a darker image. The scanner is trying to make it medium-gray. Try scanning again with a large black sheet of paper over the stamp to be scanned.
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Posted 08/22/2019   12:47 pm  Show Profile Check 51studebaker's eBay Listings Bookmark this reply Add 51studebaker to your friends list  Get a Link to this Reply
Scanners are calibrated to scan with lid closed. Scanning with lid open allows ambient light to impact how the image is rendered.

So if you scan with the lid open, the amount of ambient light detected by the CCD and then dealt with in the firmware can greatly change the inputted image. Here is an example of how the ambient light can impact the color.


Scanner manufacturers add a scanner lid for a reason, the lid is a certain color (typically white) and this is how the scanner is calibrated from the factory. If you change the scanner lid color to black or another color, you should re-calibrate your scanner with that background color.
Scanning with lid open results in all kinds of potentially new issues since the scan color will change with whatever the ambient lighting is at the time you scan. This is one of the reasons you should not scan with the lid open.

Don
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Posted 08/22/2019   1:10 pm  Show Profile Check rlsny's eBay Listings Bookmark this reply Add rlsny to your friends list  Get a Link to this Reply
Neither of these is the issue. Both scans were done with the identical source page (a black vario page). The cover was closed and the page wasn't even moved between the two scans. The only difference is that in the second scan I used the preview screen to highlight just the stamp I wanted to scan. In other words, the same page, the same conditions, the only difference was instructions to the software. 1) scan the whole page, 2) scan just a small portion of the page.

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Posted 08/22/2019   1:24 pm  Show Profile Check 51studebaker's eBay Listings Bookmark this reply Add 51studebaker to your friends list  Get a Link to this Reply
I was replying to Germania's post.

The CCD is reacting to the background color. So the scan area is small (just the area around the stamp) will get very little black background but when the scan area includes a lot of black background it tries to account for it.
Don
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Posted 08/22/2019   1:33 pm  Show Profile Check rlsny's eBay Listings Bookmark this reply Add rlsny to your friends list  Get a Link to this Reply
OK, now I think you are on to something. So there is some sort of brightness correction built in being affected by the dark/lightness of the scan area. That makes sense to me. I wonder if there is any adjustment setting to that correction algorithm. I'm guessing not, but will look. But this gives me something to work with. Basically the full page scan is picking up a lot more black. So if I want a brighter image I should see if can raise the average brightness of the scan. I feel some experiments coming.
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Posted 08/22/2019   1:48 pm  Show Profile Bookmark this reply Add wtcrowe to your friends list  Get a Link to this Reply
I use an Epson Perfection V550 Photo scanner and find that the scan can differ from time to time. Every so often things come out over exposed (in my opinion) and once in a great while underexposed (again in my opinion). I also find that the same card of stamps can get a different scan if placed midway on the platen as opposed to flush at the top.
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Posted 08/22/2019   2:03 pm  Show Profile Check 51studebaker's eBay Listings Bookmark this reply Add 51studebaker to your friends list  Get a Link to this Reply
The CCD is in the middle of the bar, so it must use a lens (think eye fish effect) to 'reach' across the entire width of the platen. So towards the middle of the platen (you can see the CCD on the bar) is where you will get your most accurate scans. But I do not think that this impacts exposure.

Exposure may be impacted by the movement of the bar. If the scanner is older, or if it suffered a drop while shipping, or if the scanner is cold, the bar movement can be affected. Cold scans will always be slightly different than a scanner which is been warmed up with 6-10 previous scans.

On the downside, really heating up your scanner (with 50+ scans in a row) will cause the lithium on the bar rails to vaporize which often results in a light haze on the under side of the glass platen.

Disassembly of the scanner unit to clean it is worthwhile if this has happened.
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Posted 08/22/2019   2:15 pm  Show Profile Check rlsny's eBay Listings Bookmark this reply Add rlsny to your friends list  Get a Link to this Reply
So I tried a few experiments. First I tried covering half the Vario sheet with a white piece of paper but scanned the whole sheet. That resulted in an even darker stamp. So adding overall brightness didn't help. I was thinking that perhaps trying to lower the amount of black would help. So I did the same thing, but this time covering the right half of the page which had fewer stamps and so more black. Again a dark stamp. So simple tricks didn't work. I then scanned all the stamps in one row only. Bright stamps. Here they are below. So I guess the message for me is if I want brighter scans, instead of one scan per page, break it up into one scan per row - something like that. Kind of a lot of work, but scan times will be short, so maybe that works.

I don't have a good explanation of why. Overall brightness or amount of black in the scan doesn't seem to change things. Smaller size scans seem to come out brighter. I'm still without a good explanation but at least I have a workaround.


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Posted 08/22/2019   6:01 pm  Show Profile Bookmark this reply Add angore to your friends list  Get a Link to this Reply
I always scan in Professional mode (as opposed to Home,etc). In this mode, Epson usually does an auto exposure on scans. The auto exposure mode is indicated by the left icon when the little triangles touch the spherical object. If you select reset on right, it removes adjustments and the object on left changes.

For me when Epson gets it wrong, I usually can just select Reset and usually looks good.




For example, if I scan a vario page full of the stamps, the auto exposure makes the black blacker and contrast is increased. After reset, it looks more like the actual sheet (black is not as black).
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Edited by angore - 08/22/2019 6:06 pm
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Posted 08/22/2019   7:41 pm  Show Profile Bookmark this reply Add cjpalermo1964 to your friends list  Get a Link to this Reply
Using the Epson software in Professional mode, what settings are required to cause the scanner to scan only a small region, e.g., 2"x2" surrounding a single stamp, rather than an entire 8.5"x11" page? I would like to see if this "area of background" problem exists on my V39.
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Posted 08/22/2019   8:12 pm  Show Profile Bookmark this reply Add rod222 to your friends list  Get a Link to this Reply

Quote:
Using the Epson software in Professional mode, what settings are required to cause the scanner to scan only a small region, e.g., 2"x2" surrounding a single stamp, rather than an entire 8.5"x11" page? I would like to see if this "area of background" problem exists on my V39.


Pre scan the platen, (click preview) (with the stamp aboard) then draw a carousel around the stamp. Re scan the carousel at whatever dpi you select (best 600dpi)
Super easy.
preview scan....

carousel drawn..........
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Edited by rod222 - 08/22/2019 8:18 pm
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Posted 08/22/2019   9:45 pm  Show Profile Check rlsny's eBay Listings Bookmark this reply Add rlsny to your friends list  Get a Link to this Reply
I'm using professional mode - all adjustments turned off. I did try turning it back on for these experiments, but it was not helpful - as expected.
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Posted 08/22/2019   9:49 pm  Show Profile Check rlsny's eBay Listings Bookmark this reply Add rlsny to your friends list  Get a Link to this Reply
I tried another experiment - which actually increased the mystery. I took a blank black Vario page and put one stamp on it. I scanned the full page, the row, and just the stamp. In all three the one stamp came out exactly the same - quite brightly exposed. So clearly just scan size is not an explanation.

Could be aliens.

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Posted 08/22/2019   10:08 pm  Show Profile Bookmark this reply Add Louise411 to your friends list  Get a Link to this Reply
Since the Vario is plastic it might reflect light perhaps? I had a white cover under the hood which had acquired some spring or give from much use and maybe that is it.
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Posted 08/22/2019   10:14 pm  Show Profile Bookmark this reply Add revcollector to your friends list  Get a Link to this Reply
I suspect that it might have something to do with the relative number of pixels per total area. The percentage of pixels actually used to produce the stamp image when cropped is very high, but for the stamp on the full page it is very low. The image is brighter because the density is greater.
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