AN Glass on Epson 4990

[Ari]

I've been wanting to scan my 4x5s full frame, but I can't do so with the holders that came with the 4990.
So I thought to get some AN glass here:

http://cgi.ebay.com/Yanke-Anti-Newto...ht_2354wt_1165

and scan up to four sheets, full frame, without having to open and close the scanner, change negs, etc..
The glass is 1.1mm thick.

Can anyone tell me if that is the correct thickness for the 4990 (it looks to be so), and whether or not this is a hare-brained idea before I go and buy the glass?

Also, the dimensions of the glass are 210mm x 250mm; is it better to cut a piece that will fit exactly the 4990's bed (225mm x 303mm)?

Thanks in advance.

[Frank Petronio]

You need room for tape and handling, so u do one at time. I would get it large enough to hold 8x10 plus tape and fingers. I place mine on top of pennies and have it smaller than the platen.

[Zaitz]

When I sandwich the negative between 2 8x10 pieces of glass and have the AN glass on top like the instructions say I still get bad newton rings. If I place the negative just on the scanner glass (not optimal sharpness) then they are gone.

[Ari]

I was thinking of placing the AN glass on top of the scanner bed (platen), put the negative on top of that, and then scanning.
The glass should give the same height from film to platen as does the plastic negative holder.

[Zaitz]

The instructions I have from FocalPoint say to have (from top to bottom):

an glass etched side down
negative
scanner glass

[Ari]

Isn't that the reason you are getting less than optimal sharpness, though?

[Zaitz]

Isn't that the reason you are getting less than optimal sharpness, though?

If I place a clear piece of glass on the bottom to sandwich the negative then I still get newton rings even with the AN glass on top as the instructions say. Without the extra clear glass I don't get newton rings but don't get optimal sharpness.

[Ari]

Why not leave the top open, perhaps taping down the film, as Frank suggests?
You'd be using only one piece of AN glass, and you might get both issues, sharpness and Newton rings, resolved in one fell swoop.

From the bottom up:
scanner glass
AN glass (not sure about the orientation)
negative

I'd like to know if that makes any difference for you.

[Zaitz]

Why not leave the top open, perhaps taping down the film, as Frank suggests?
You'd be using only one piece of AN glass, and you might get both issues, sharpness and Newton rings, resolved in one fell swoop.

From the bottom up:
scanner glass
AN glass (not sure about the orientation)
negative

I'd like to know if that makes any difference for you.

I figured it muck up the scan having the AN glass first! I'll try it soon.

[Ari]

Please let me know.
a) I'm curious
b) you might have a spare piece of AN glass to sell