shimming the glass?

[alanrockwood]

The Epson V700/V750/V800/V850 scanners have fixed focus. People shim the film holder to give a height-above-glass that provides the best focus. In my testing so far I am finding the optimum focus to be higher than the highest adjustment tabs on the stock film holders (3.5mm). My testing is not done yet, but I am becoming suspicious that the optimal height above the glass may vary at different points on the glass, possibly because of some tilt in the glass.

In principal one could fix this by placing shims under the glass to bring it to an optimal position and to remove any tilt that may be in the glass mounting. Let us suppose one shimmed the glass so that when using the 3mm height adjustment tabs on the film holders the scanner was in perfect focus. Let us further suppose that one can shim the glass to the optimal height is 3mm at every point on the glass.

Shimming the glass would be a far better way of dealing with a tilt in the glass mount than trying to fiddle with adjustments in the film holders.

Has anyone tried this?

 

[Mainecoonmaniac]

If I'm reading this post correctly, you want to remove the glass from the scanner and shim under the platen glass? I would not. If you want to have precise height adjustment, I recommend this.
http://www.betterscanning.com/scanning/models/vseries.html

There are nylon screws that you can adjust the height of the scanner glass. I have a V700 and it vastly improved the sharpness.

 

[jtk]

If I'm reading this post correctly, you want to remove the glass from the scanner and shim under the platen glass? I would not. If you want to have precise height adjustment, I recommend this.
http://www.betterscanning.com/scanning/models/vseries.html

There are nylon screws that you can adjust the height of the scanner glass. I have a V700 and it vastly improved the sharpness.

I use that system with an ancient Epson 3200. Anything else is a compromise... those nylon screws allow finer adjustment than tape thickness and that can be seen in scans..

 

[GRHazelton]

If I'm reading this post correctly, you want to remove the glass from the scanner and shim under the platen glass? I would not. If you want to have precise height adjustment, I recommend this.
http://www.betterscanning.com/scanning/models/vseries.html

There are nylon screws that you can adjust the height of the scanner glass. I have a V700 and it vastly improved the sharpness.

I use the BetterScanning holder for 120 and anti-Newton's Rings glass on my Epson 700.While the setup is fiddly the improvement in sharpness is worth the effort. The ANR glass helps compensate for the "floppiness" of 120 film.

 

[Mainecoonmaniac]

I use the BetterScanning holder for 120 and anti-Newton's Rings glass on my Epson 700.While the setup is fiddly the improvement in sharpness is worth the effort. The ANR glass helps compensate for the "floppiness" of 120 film.

Better Scanning carriers are a bit harder to use, but sharper. The film has to be taped to the glass then masked off. But it's a huge improvement.

 

[shutterfinger]

Download the V700 Service Manual here: https://www.manualslib.com/manual/1000666/Epson-Perfection-V700-Photo.html
Once the top of the bed is removed you will find the glass sealed with thin double sided tape and several metal clips with screws around the perimeter of the glass.
Before opening the scanner I would lay a rigid straight edge across the bed and measure to the glass in several places both vertical and horizontal with a caliper to identify any unevenness if any exists.

 

[alanrockwood]

Download the V700 Service Manual here: https://www.manualslib.com/manual/1000666/Epson-Perfection-V700-Photo.html
Once the top of the bed is removed you will find the glass sealed with thin double sided tape and several metal clips with screws around the perimeter of the glass.
Before opening the scanner I would lay a rigid straight edge across the bed and measure to the glass in several places both vertical and horizontal with a caliper to identify any unevenness if any exists.

Thanks for that helpful reply. It sounds like you may have opened one of these up before. If so, do you think there are reasonable shimming points? If so, then as far as shape and thickness of shims is concerned, I can probably whip up some plastic shims of of the right size and dimensions on my 3D printer.

 

[shutterfinger]

I opened mine to clean the under side of the bed glass. As best I remember the glass overlaps the opening by 3/16 to 1/4 inch each side. There is no way I could see to raise the glass, only lower it. I have not optimized mine with the better scanning holder but the negative emulsion side on the bed glass with AN glass on top gives good results. I still think the Microtek 8700 Pro gave better results as it was glassless. I've considered removing the bed glass and replacing it with a edge frame that the holders will sit on to make it glassless, film dedicated.

 

[Born2Late]

If I'm reading this post correctly, you want to remove the glass from the scanner and shim under the platen glass? I would not. If you want to have precise height adjustment, I recommend this.
http://www.betterscanning.com/scanning/models/vseries.html

There are nylon screws that you can adjust the height of the scanner glass. I have a V700 and it vastly improved the sharpness.

I have a V850 and contacted Better Scanning about 35mm negative carriers. They told me that they have nothing for 35mm for the 850 and really didn't seem all that imterested. They really didn't leave me with a warm fuzzy feeling.

 

[alanrockwood]

I opened mine to clean the under side of the bed glass. As best I remember the glass overlaps the opening by 3/16 to 1/4 inch each side. There is no way I could see to raise the glass, only lower it. I have not optimized mine with the better scanning holder but the negative emulsion side on the bed glass with AN glass on top gives good results. I still think the Microtek 8700 Pro gave better results as it was glassless. I've considered removing the bed glass and replacing it with a edge frame that the holders will sit on to make it glassless, film dedicated.

Thanks for the info. I may need to abandon the idea of shimming the glass.
If you remove the glass please be aware that you will need to re-measure the effective film height. The glass shortens the effective path length of the light, so the film will need to be a little higher if you remove the glass. You can actually calculate how much higher if you know the refractive index of the glass and the thickness of the glass, or you could guess at the refractive index (probably around 1.6) and measure the glass thickness. That should get you close enough. I don't have the path length formula handy right now. I can find it it you want.

 

[alanrockwood]

By the way there is a thread titled "Epson V700/V750 focus height...finding the sweet spot." here at photrio that has some relevant information.