Minimizing Moire patterns when scanning large format negat..

In article <BKrcg.87443$TK1.10443@fed1read06>,
"Terry Smith" <TMSmith DeleteThis @abriget.com> wrote:

> How does one test for optimal focus? By trying dozens (or perhaps hundreds)
> of heights above the glass? And how does one do that? With increasing
> numbers of individual sheets of paper?
>
> This scanner world is getting pretty difficult...

If you want to do digital,........
--
The sometimes insomniac.

www.gregblankphoto.com
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

Already did that with a Nikon D2X, but I still LOVE large format
photography. As good as a D2X is (or a 1Ds Mark II), there's something
about a LF neg...



"Greg "_"" <grey_egg.RemoveThis@greg_photo.com> wrote in message
news:grey_egg-54845C.19463122052006@news.isp.giganews.com...
> In article <BKrcg.87443$TK1.10443@fed1read06>,
> "Terry Smith" <TMSmith.RemoveThis@abriget.com> wrote:
>
>> How does one test for optimal focus? By trying dozens (or perhaps
>> hundreds)
>> of heights above the glass? And how does one do that? With increasing
>> numbers of individual sheets of paper?
>>
>> This scanner world is getting pretty difficult...
>
> If you want to do digital,........
> --
> The sometimes insomniac.
>
> www.gregblankphoto.com
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

"Greg "_"" <grey_egg.TakeThisOut@greg_photo.com> wrote:
>
> What do you think of the V750,

It looks good on paper. (My theory is that film really doesn't have any more
than 2700 ppi of real, usaable information on it, so the Epson scanners
(which only have effective resolutions about 1/2 their claimed resolution)
should be getting close to getting everything that's there.)

>....and man you keep some strange
> hours..... or is it morning there?

Both of the above. It's 8:12 am right now. (Also, I work at home, so unless
I'm out bowling, I'm probably in front of the computer.)

David J. Littleboy
Tokyo, Japan
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

In article <e4tguq$s19$1@nnrp.gol.com>,
"David J. Littleboy" <davidjl.TakeThisOut@gol.com> wrote:

> "Greg "_"" <grey_egg.TakeThisOut@greg_photo.com> wrote:
> >
> > What do you think of the V750,
>
> It looks good on paper. (My theory is that film really doesn't have any more
> than 2700 ppi of real, usaable information on it, so the Epson scanners
> (which only have effective resolutions about 1/2 their claimed resolution)
> should be getting close to getting everything that's there.)
>
> >....and man you keep some strange
> > hours..... or is it morning there?
>
> Both of the above. It's 8:12 am right now. (Also, I work at home, so unless
> I'm out bowling, I'm probably in front of the computer.)
>
> David J. Littleboy
> Tokyo, Japan

The thing that has my whiskers and fur standing up is that the 35mm & MF
scanning looks good with the V700 & by default that should mean the
V750 will get good marks too. I'll wait for the reviews-but it could be
time for an upgrade

How good of a bowler are you.....ducks or ten pin?
--
The sometimes insomniac.

www.gregblankphoto.com
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

"Greg "_"" <grey_egg.DeleteThis@greg_photo.com> wrote:
>
> How good of a bowler are you.....ducks or ten pin?

I'll average 200 or so on a good day. Don't ask about the bad days.

David J. Littleboy
Tokyo, Japan
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

In article <e4tjc7$skk$1@nnrp.gol.com>,
"David J. Littleboy" <davidjl RemoveThis @gol.com> wrote:

> "Greg "_"" <grey_egg RemoveThis @greg_photo.com> wrote:
> >
> > How good of a bowler are you.....ducks or ten pin?
>
> I'll average 200 or so on a good day. Don't ask about the bad days.
>
> David J. Littleboy
> Tokyo, Japan

Thats excellent for duckpins
--
The sometimes insomniac.

www.gregblankphoto.com
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

Thanks Kevin. This has been recommended (as well as argued against) as a
solution, but heck, I'll give it a try!


"k-man" <kmccrack.RemoveThis@gmail.com> wrote in message
news:1148389661.962193.81290@j33g2000cwa.googlegroups.com...

> I'm a large format photographer using an Epson 4870 scanner to scan my 5x7
> negatives. I've had a custom 5x7 carrier made to hold the negatives
> (similar to the 4x5 transparency carrier that came with the scanner). In
> general, this setup work quite well, but I'm getting moiré patterns,
> especially in the middle of the negatives where there is a lot of single
> tonality area (like open sky) mostly on B&W negatives.
>
> Does anyone have a clue on how to minimize this moiré pattern problem?
> (and no, I'd rather not send my negs out to be drum scanned... <s>)
>

I used to experience a similar problem. In the center of my negatives,
I would get what looked like almost an oil immersion effect. Really
annoying. I solved the problem by flipping the negative over so that
it curved in the opposite direction (If you looked at the negative
end-on, the short egde was curved up, like a smile. That's when I
would see the problem. When I flipped over the negative such that the
short egde looked like a frown, that's when the problem would go away).

Kevin
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

"Greg "_"" <grey_egg.TakeThisOut@greg_photo.com> wrote:
> "David J. Littleboy" <davidjl.TakeThisOut@gol.com> wrote:
>
>> "Greg "_"" <grey_egg.TakeThisOut@greg_photo.com> wrote:
>> >
>> > How good of a bowler are you.....ducks or ten pin?
>>
>> I'll average 200 or so on a good day. Don't ask about the bad days.
>
> Thats excellent for duckpins

Although I'm from Boston, I've never even seen duckpins, even on the tube.
Are there any duckpin lanes outside New England?

David J. Littleboy
Tokyo, Japan
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

In article <e4tp25$u4k$1@nnrp.gol.com>,
"David J. Littleboy" <davidjl DeleteThis @gol.com> wrote:

> "Greg "_"" <grey_egg DeleteThis @greg_photo.com> wrote:
> > "David J. Littleboy" <davidjl DeleteThis @gol.com> wrote:
> >
> >> "Greg "_"" <grey_egg DeleteThis @greg_photo.com> wrote:
> >> >
> >> > How good of a bowler are you.....ducks or ten pin?
> >>
> >> I'll average 200 or so on a good day. Don't ask about the bad days.
> >
> > Thats excellent for duckpins
>
> Although I'm from Boston, I've never even seen duckpins, even on the tube.
> Are there any duckpin lanes outside New England?
>
> David J. Littleboy
> Tokyo, Japan

I have not been to a Bowling alley in probably 10 years+ in any event
last time I was, most alleys had about half the lanes devoted to duck
pins. Here in Maryland.
--
The sometimes insomniac.

www.gregblankphoto.com
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

"Terry Smith" <TMSmith DeleteThis @abriget.com> wrote in message
news:BKrcg.87443$TK1.10443@fed1read06...
> How does one test for optimal focus?

Often the optimal focus for transilluminated film is in the order of
0.5 - 1.0 mm above the glass platen (to accomodate mounted slide film)
and there are usually holders for other film (sheets/strips) that also
position the film at about the same height.

So all it takes is something as simple as a wooden match stick, wood
because it won't scratch the glass and it has some structure, with one
end resting on the glass and the other end raised by a known/measured
height above the glass. If the best focus is e.g. halfway the stick
then optimal focus is at half the height.

More elaborate methods can be used, but there is also a certain depth
of field that can be exploited. As long as the film is held flat,
everything is at the same level of focus accuracy.

Bart
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

Ok that said how would you look at the scan and evaluate wether
it was in fact sharp as a result of that positioning versus the
standard position found in the as is film holder placement.

If there is a good online resource for this info will someone
provide? I hear Rafe tapping at his keyboard as I write this
adding a new set of info to his site


In article <447393c4$0$31649$e4fe514c@news.xs4all.nl>,
"Bart van der Wolf" <bvdwolf.DeleteThis@no.spam> wrote:

> "Terry Smith" <TMSmith.DeleteThis@abriget.com> wrote in message
> news:BKrcg.87443$TK1.10443@fed1read06...
> > How does one test for optimal focus?
>
> Often the optimal focus for transilluminated film is in the order of
> 0.5 - 1.0 mm above the glass platen (to accomodate mounted slide film)
> and there are usually holders for other film (sheets/strips) that also
> position the film at about the same height.
>
> So all it takes is something as simple as a wooden match stick, wood
> because it won't scratch the glass and it has some structure, with one
> end resting on the glass and the other end raised by a known/measured
> height above the glass. If the best focus is e.g. halfway the stick
> then optimal focus is at half the height.
>
> More elaborate methods can be used, but there is also a certain depth
> of field that can be exploited. As long as the film is held flat,
> everything is at the same level of focus accuracy.
>
> Bart
--
The sometimes insomniac.

www.gregblankphoto.com
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

"Greg "_"" <grey_egg.RemoveThis@greg_photo.com> wrote:
> Ok that said how would you look at the scan and evaluate wether
> it was in fact sharp as a result of that positioning versus the
> standard position found in the as is film holder placement.

Hehe. You've found the crux of the matter; everything looks somewhat fuzzy.

What I ended up doing was putting a nasty scratch in a frame (to have a nice
sharp edge to image) and scanning that frame at an angle.

>> So all it takes is something as simple as a wooden match stick, wood
>> because it won't scratch the glass and it has some structure, with one
>> end resting on the glass and the other end raised by a known/measured
>> height above the glass. If the best focus is e.g. halfway the stick
>> then optimal focus is at half the height.

What Bart said.

David J. Littleboy
Tokyo, Japan
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat.. 

In article <e50aot$kfg$1@nnrp.gol.com>,
"David J. Littleboy" <davidjl RemoveThis @gol.com> wrote:

> "Greg "_"" <grey_egg RemoveThis @greg_photo.com> wrote:
> > Ok that said how would you look at the scan and evaluate wether
> > it was in fact sharp as a result of that positioning versus the
> > standard position found in the as is film holder placement.
>
> Hehe. You've found the crux of the matter; everything looks somewhat fuzzy.
>
> What I ended up doing was putting a nasty scratch in a frame (to have a nice
> sharp edge to image) and scanning that frame at an angle.
>
> >> So all it takes is something as simple as a wooden match stick, wood
> >> because it won't scratch the glass and it has some structure, with one
> >> end resting on the glass and the other end raised by a known/measured
> >> height above the glass. If the best focus is e.g. halfway the stick
> >> then optimal focus is at half the height.
>
> What Bart said.
>
> David J. Littleboy
> Tokyo, Japan

Why not put five or so scratches then???? Hell scratch the whole thing
:^)

Seriously 5 numbered scratches, one each corner and the middle would tell
lots I think. X marks the spot!
--
The sometimes insomniac.

www.gregblankphoto.com
 >> Stay informed about: Minimizing Moire patterns when scanning large format negat..