Resolution of the Epson V700

[Alan Johnson]

I made a 35mm Agfa Copex Rapid microfilm negative of a test target photographed from the correct distance with a Canon 50mm f1.8 at f5.6.
Under the microscope 125 line-pairs/mm is visible on this negative.
The attachment shows the result of scanning with the V700.Only a very small part of the negative is shown.
The film holder was set to the + position, the negative emulsion side down, the negative held down by a betterscanning.com ANR glass jammed down with pieces of card against the vertical plastic posts on the film holder,scanned at 4800dpi and sharpened three times at 100 amount 1 radius and 0 threshold.
If the result is taken as 50 lppm, this is 50x2x25.4 = 2540 dpi for the resolution of this V700.
This is a little higher than sometimes quoted, I got curious to make this measurement after seeing the scatter in other results.

 

[ctscanner]

Alan,

Just a curiosity question, but I wondered what the reason would have been to sharpen the scan three times. Is this SOP for a process like this?

George

 

[Alan Johnson]

It's really just personal preference.I find it easier to add sharpness in small increments and see the effect with the preview button.
btw, the resolution value seems to depend on the amount of contrast between the light and dark lines that is considered acceptable.There is still a little contast left at 65 lppm or 65x2x25.4 =3300 dpi.
But I assume that the amount of contrast at 50 lppm, 2540 dpi is more typical of that used to quote resolution.

Alan

 

[sanking]

Alan,

Just a curiosity question, but I wondered what the reason would have been to sharpen the scan three times. Is this SOP for a process like this?

George

My SOP when testing scanners with a target is to not use any sharpening routine at all. I simply adjust the scan of the target for maximum contrast and read the results. I think the use of sharpening routines makes it virtually impossible to relate one person's test to another.

My test of the Epson V700, using the 1951 USAF target, gives maximum resolution of 2300 spi when scanning at 6300 spi, after adjusting for the best plane of focus and using the sharper of the two lenses. Tests by www. scandig. com also show 2300 spi.

Sandy

 

[ctscanner]

Alan, Sandy,

Gentlemen, thanks for the information. I was not familiar with the process and interested in what was being attempted.

George

 

[Marco B]

If the result is taken as 50 lppm, this is 50x2x25.4 = 2540 dpi for the resolution of this V700.
This is a little higher than sometimes quoted, I got curious to make this measurement after seeing the scatter in other results.

My test of the Epson V700, using the 1951 USAF target, gives maximum resolution of 2300 spi when scanning at 6300 spi, after adjusting for the best plane of focus and using the sharper of the two lenses. Tests by www. scandig. com also show 2300 spi.

Sandy

I think this difference of a mere 250 ppi is well within the range of error of any scanner resolution test, and so negligible...

This is also confirmed by the scan you posted: just look at the difference between the vertical lines and the horizontal lines in the 50 lp/mm section. The vertical lines are rendered far more fuzzy and unsharp than the horizontal lines, and could easily lead to a different conclusion.

Any judgements of scanner resolution not done using exactly the same test charts and equipment, will hence cause a rather large diffuse error zone.

 

[sanking]

Any judgements of scanner resolution not done using exactly the same test charts and equipment, will hence cause a rather large diffuse error zone.

In fact even when using the same tests there is some subjectivity in evaluating a target. If you go to www.scandig.com and look at the test for the Nkon LS-9000 you will see that the reviewer determined that the scanner gave resolution of 3900 dpi in the test. I look at the same test and only see about 3250 dpi. When I read these targets the resolution line is where there is clear discrimination in both the vertical and horizontal lines, not in just one or the other.

Sandy King

 

[Alan Johnson]

From the vertical lines on my test chart, 45 lppm seems a better estimate.
45x2x25.4 = 2286 ~ 2300dpi ~7m-pixels for 35mm film.

But some low contrast separation can be seen at 65 lppm.
65x2x25.4 =3300 ~ 14.6 m-pixels for 35mm film.

I suppose it's a matter of personal opinion but my impression of prints from the V700 is that it is better than a 7 m-pixel device but not as good as a 15 m-pixel. Simply using the 2300 dpi figure ( 7 m-pixels) underestimates how good the V700 is.