[rollei_list] Re: ADMIN: Petr's tone
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Fri, 27 Nov 2009 13:30:22 -0300
Your final statement is your statement, it is not my statement, you
are insisting again with the Epson Perfection scanners provided with
dual lenses system for different resolution size scanning that in my
second post I wrote I was wrong to include them in the first
statement. It's clear that there are enough samples saying that the
best focus for the _newest_ Epson scanners are on the glass from 0 to
0.5mm that it could be not by chance. These are more samples, this
time with the newer Epson v500:
"I did a test of my v500 on a resolution target and found the focus
was good for about 800 lines per inch from 0 to .5mm plus the film
thickness from the surface of the glass, going from 2400 to 4800 dpi
made no real differences, 3200 DPI seems to be optimal for 35mm while
2400 dpi seems to be best for 120, kind of explains why you have to go
to medium format to get a worth while size print. Also explains why a
special film holder is not going to buy you much with the v500 optics
and it's LED illumination.
This confirmed the results of wet scanning with the film right against
the glass"
http://www.flickr.com/photos/metrix_feet/2157756897/
"Interesting I did a focus check at 4800dpi by ramping a piece of
frosted glass. Everything is in relatively good focus from 0 to 0.5mm
from the glass scanning surface for the V500. This is a very good
depth of field. It seem the optics have been designed to be tolerant
of film that is not flat. This kind of explains why I can do a scan
with the film directly on the scanner and covered with a piece of anti
glare glass and it seems to be as well focused as when I use the slide
holder. It also explains why I can do the wet scan without using a
mylar spacer."
http://www.flickr.com/photos/metrix_feet/2643076036/
Carlos
2009/11/27, Petr Dvorak <pdvorak@xxxxxxxxx>:
> Thank you Carlos,
>
> It should be easier from now on.
> >> 1. Epson says: for some of the newer scanners (single-lens fixed focus),
> the
> >> focus and best film position is above the glass: yes/no
> > > yes
> >
>
> We have an agreement here. Good.
>
> > >> 2. You say: I interpret that "above the glass" means "on the glass":
> yes/no
> > > yes
> >
>
> I follow you there. Good. I disagree with you. Bad. I say "0.2mm height
> difference has visible impact on sharpness of scans", and I put my acts
> where my mouth is by providing you with a link to my experiment results in
> one of the previous threads
>
> >
> > >> 3. Epson statement therefore is (as you put it in your email): the best
> > >> focus can be obtained on the glass: yes/no
> > > yes
> >
>
> Uh oh, we have a train wreck here. You contradict point #1. For me, "above
> the glass" is not equal to "on the glass". We interpret the written text
> differently, and from now on, we cannot come the same conclusions.
>
> >
> > > 4. You say: we should scan from the bed on all Epson scanners, you will
> get
> > > the best results: yes/no
> >
> > Yes, at least Epson states that it is the point
> >
>
> No Carlos. Epson states "above the glass". You interpret it "on the glass".
> Those are two different terms.
>
> >
> > It was a typo, my scanner is the 4490, anyway my scanner is included
> > in the first site too. BTW I just measured the film height on the
> > glass using the Epson MF holders, it's about 0.5mm or .5mm and then I
> > did not find interesting those holders, I know that site from some
> > years ago and read it several times and watching the results I
> > obtained from my scanner with the standard holder and scanning on
> > glass, I never wanted to buy one of those holders.
> >
>
> I am okay with that. I measured the actual focus distance on my former Epson
> 3180 and it was above the height of the film holder's plane. You cannot draw
> general conclusions from your unit only.
>
> > Yes, it's true that no two scanners are alike, like two camera lenses
> > are not alike, but according my limited experience with scanners, I
> > doubt those differences could be enough to justify to change holders,
> > etc., I don't know the way the scanner focus is adjusted in factory.
> > Several aerial cameras have different lenses or the same lens but
> > have the focus adjusted to infinity. I could think that the scanners
> > focus is adjusted for the same point in spite of the manufacturing
> > difference and I also could think that the scanner lens DOF has to do
> > with the manufacturing differences control . I don't know the way the
> > film flatness is controlled in the tests you are mentioning. BTW, it
> > could happen that some scanners out of the factory specs calibrations
> > could need those no standard holders.
> >
>
> We are in a good agreement about a few points there. I like that you say "I
> think" instead of "Epson says". Please leave the aerial cameras aside, this
> topic is complicated enough already. My flatness is controlled by wet
> mounting of film on a piece of glass. Beat that.
>
> > I did not generalize, the Epson document generalized, but I must say
> > that my scannings on the scanner glass never were worse than using the
> > film holder, they were similar or better slightly.
> > Carlos
>
> Carlos, do not put your words in Epson's mouths. Epson says above the glass.
> You say on the glass. On the other hand, I value your experience.
>
> >PS: BTW, there more than two gentlemen scanning on the scanner glass
> in this group.
>
> And that is perfectly Ok with me. Bear with me for one more second and let
> me wrap up.
>
> In you first email, you stated: "ALL Epson Perfection scanners with fixed
> focus lenses are focused on the glass directly. Therefore the glass surface
> is where the highest sharpness can be obtained, film holders are useful
> because they compensate lack of sharpness with better film flatness and
> eliminate Newton rings. There is no point in discussing this because Epson
> says that in the document."
>
> Under the weight of arguments, we will eventually come to this restatement:
> "SOME of the Epson scanners (excluding all models with dual lens system,
> which includes the V5xx, V7xx and V9xx models) have (by design) their focus
> plane set ABOVE the bed. The actual distance varies between units thanks to
> manufacturing and calibration differences. While the actual distribution of
> these distances is not exactly known to us, there probably exists a set of
> scanners that may achieve sharper results off a plane more distant from the
> bed, and there also exists a set of scanners that scan off the bed sharper
> than off the film holder, as is the experience of mine and of two additional
> colleagues from this forum. This has nothing to do with film flatness in
> film holders. I encourage you to experiment and share your experience with
> us in this forum so we can compare where the actual focus plane in our units
> is."
>
> For me, those two statements are like day and night. I am not going to ask
> you if you see that difference too because I am afraid of your answer.
>
> Regards,
> P.
---
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