RE: [APML] 4x5 astrocamera (again?)

["D. Kodama" <kodama@alumni.caltech.edu>]

Loke,

Correction -- I was looking at the wrong graph.  My scope's spec states
that the spot size gets as small as 14 microns.  So it would seem that if
this is true, with the right film I could be undersampling at 2500 DPI.

Dave



> Loke,
>
> That should be so, but I wonder sometimes.  I would think that I should be
> able to distinctly see the film grains in scans if I were oversampling the
> film but I can't see it on the finer grain films like E100.
>
> The spot size spec for my 4" scope (the only one I have info on) is 30
> microns so 25 micron sampling is not enough for that.  The question is the
> particular film itself.  I haven't pursued it further, but I have wondered
> if the combination of the film grains randomly "sampling" the image plus
> the scanner's uniform pixel sampling shouldn't be taken into account when
> trying to determine the critical scanner sampling frequency.
>
> At any rate, I prefer to be conservative about the scanning.  If you have
> some information on definitive studies on films and scanning, I'd be
> interested in hearing about them.
>
> Dave
>
> P.S.  Eventually I hope to try tricolor tech pan also.  For that I would
> think I definitely need the full scanner resolution.
>
>
>
>
>> Dave,
>>
>>  When you scan at 2500 dpi, this is equivalent to 10um per pixel. Does
>> your
>> color film have this resolution? Probably not. I would guess that even
>> 25um
>> per pixel is more resolution than the film plus optics gives. So all the
>> extra data gives you no additional information. You might as well scan
>> at
>> a
>> lower resolution.
>>
>> Loke
>>
>>
>>
>>
>>> -----Original Message-----
>>> From: astro-photo-bounces@seds.org
>>> [mailto:astro-photo-bounces@seds.org]On Behalf Of D. Kodama
>>> Sent: Friday, May 07, 2004 9:55 PM
>>> To: astro-photo@seds.org
>>> Subject: Re: [APML] 4x5 astrocamera (again?)
>>>
>>>
>>>
>>> Wei-Hao,
>>>
>>> Thanks for the info on 4x5 film choices.  I recently picked up my own
>>> combo 4x5" and 6x9cm setup (Mitsuboshi) so the info is appreciated.
>>>
>>> Regarding E100SW, awhile back I tried it in 4x5 format but found that
>>> it
>>> had a tendency to go to yellow-green on long exposures.  I thought the
>>> "W"
>>> (warm) version of E100 would have better red response for nebulosity,
>>> but
>>> the green seems to overwhelm things.  I'd be interested in hearing if
>>> anyone has had a similar result.  I just shot a couple of test frames
>>> before becoming too busy to proceed further.
>>>
>>> By the way, one of the "downsides" of 4x5" is the size of the digital
>>> files.  My scanner can only do 2500 DPI, but at that resolution a
>>> 48-bit
>>> TIFF file is 750,000,000 bytes!
>>>
>>> Dave Kodama
>>>
>>>
>>> > Date: Thu, 6 May 2004 15:27:29 -1000 (HST)
>>> > From: Wei-Hao Wang <wang@IfA.Hawaii.Edu>
>>> > Subject: Re: [APML] 4x5 astrocamera (again?)
>>> > To: astro-photo@seds.org
>>> > Message-ID: <200405070133.i471Xml07592@galileo.ifa.hawaii.edu>
>>> > Content-Type: TEXT/plain; charset=us-ascii
>>> >
>>> > Hi Bobby,
>>> >
>>> > Yes, E100S is discontinued.  Now only 4x5 format (perhaps some
>>> > 120 format E100SW) is available.
>>> >
>>> > Wei-Hao
>
>
>

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