How sensitive is the Epson V700 to source height above glass?

[Leonard Evens]

I've now done 0.8, 1.6, and 2.4, i.e., one, two, and three full turns from base. (I tried to measure the extensions of the white screws with a dial caliper, and I don't get those measurements, but I will use the figures given by betterscanning.) They get progressively sharper. I am not sure what to do now, since there isn'tt much further I can go with the screws provided by betterscanning. The reference provided above showed the optimal distance to be 3.2 mm. I may be able to get that high by one last full turn of the screws, but the support is likely to be pretty wobbly. Also, I won't be able to go beyond that to determine what my optimum is if it is a bit hgiher.

Any suggestions?

It is not as bad as I thought. I forgot to take the thickness of the support for the glass in the film holder into account. It added more than a mm to the overall height.

So my last measurment was in fact at about 40 mm above the scanner glass. I've now also tried going down to about 36 mm above the scanner glass, and I can't see any difference from 40 mm. I think the optimal height is between 30 and 40 mm, as noted in the above reference. I may do some more measurements, but if I leave it at about 36 mm, I think it will be more than good enough for scanning 4 x5 negatives.

[Marc B.]

Don't forget those pesky decimal points. I'm sure you mean 3.6mm to 4.0mm(?).

[Tony Evans]

Leonard,

"I tape the emulsion side of the film to the dull side of the holder glass and place the glass in the frame with the film base facing downard towards the scanner glass."

For dry scanning, I think it is "tape the film base to the ANR side of the glass and place the glass in the frame with the emulsion side downward towards the scanner glass" ie: Film is under glass with emulsion side facing downwards. Measuring height then does not include the glass thickness.

[Leonard Evens]

Don't forget those pesky decimal points. I'm sure you mean 3.6mm to 4.0mm(?).

Yes indeed!

[Greg Lockrey]

FWIW, the maximum resolution for the lens in those Epson v700 is about 2000 dpi.... any thing more than that is just wasting memory. 6400 is an interpolated number that "looks good" on the box.

[Leonard Evens]

Leonard,

"I tape the emulsion side of the film to the dull side of the holder glass and place the glass in the frame with the film base facing downard towards the scanner glass."

For dry scanning, I think it is "tape the film base to the ANR side of the glass and place the glass in the frame with the emulsion side downward towards the scanner glass" ie: Film is under glass with emulsion side facing downwards. Measuring height then does not include the glass thickness.

Perhaps I didn't explain it well enough. Indeed, the film was taped to the underside of the glass in the holder, so the holder glass thickness didn't add to the height. But, betterscanning suggested that I tape the emulsion side to the ANR side of the holder glass since in that case I would be putting the tape on the film base, which was preferable to putting it on the emulsion side. This does have the disadvantage that the film base lies between the image in the emulsion and the scanner glass, whereas if I did it as you suggest, there would be nothing between the image in the emulsion and the scanner glass. Be that as it may, I don't think the optics is affected significantly by having the light rays pass through the film base. And in addition to betterscanning's argument, if I have the film base pointing downward, I don't reverse the orientation.

[Heroique]

Actually, looks like the illustrations at Betterscanning show base side on glass.

(The film notches above the white glove indicate emulsion side is “up.”)

I’ve done both ways, and my personal results are best the opposite way – emulsion side on glass – but others here w/ reasons of their own prefer base side on glass, like the photo below.

The critical point, of course, is to tape the film sheet on the ANR (etched) side of the glass – and use more than four pieces of tape! I usually use at least 6 or 8 pieces to better ensure flatness.

[Kirk Gittings]

FWIW, the maximum resolution for the lens in those Epson v700 is about 2000 dpi.... any thing more than that is just wasting memory. 6400 is an interpolated number that "looks good" on the box.

[Brian Ellis]

Yes indeed!

That's a relief. I was puzzled as to how a scanner with a negative held almost two inches above the glass would work. : - )

[D. Bryant]

Be that as it may, I don't think the optics is affected significantly by having the light rays pass through the film base. And in addition to betterscanning's argument, if I have the film base pointing downward, I don't reverse the orientation.

Optically this is exactly analogous to printing sheet film in an enlarger with a glass negative carrier.

I've never had any IQ issues with the Betterscanning wet mount sheet film holder. Usually crud on the bottom of the scanner platen is more of a concern. Seems like you are making this more difficult than need be, at least that is what I take away from your posts.