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Re: (meteorobs) OT: Film for comet photos

In reality, there is a third reason why some people don't manipulate their 
images and are concerned with color response and with grain, and speed of 
film etc..  That is we are purists when it comes to using film and gathering 
images.  In Black and White photography there has always been a purist 
following, which never bent to even Kodaks ways.  That is why you have a 
company that has reversed engineered a film like Kodaks double XX, which can 
now be found as BPF200.  That is why you can still find films such as the 
Foma brand, or the Forte films.  Even Ilfor has not given in to even the 
T-grain revolution as fully as some people think.  Their FP4+ and FP5+ are 
still old technology films.  Only their Delta films use T-grain technology.  
Everywhere yo look in Black and White photography, you can find example 
after example of where people just prefer the older techniques.  So 
manipulating yo images might be fine for yo, but they are not for me.


>From: "Robert Warren" <rigel_ori@hotmail.com>
>Reply-To: meteorobs@atmob.org
>To: meteorobs@atmob.org
>Subject: Re: (meteorobs) OT: Film for comet photos
>Date: Tue, 10 Jul 2001 08:14:25 -0400
>
>It is interesting that some people are using such software packages as
>"photshop".  However, in cometary astronomy, there are two basic problems 
>in
>doing so.  The first is if you manipulate the color of the image, you could
>be losing valuable information.  The color of the comets tail, or coma, or
>even nuclear region are indicative of what parent moecules are being
>released from the nucleus.  The Color response of the film can detect only
>certain molecules, because each and evey molecule can only emit certain
>wavelengths of light, or spectral lines.  So the color response of the film
>is very important.  It is obvious that you do have some understanding of 
>the
>problems with grain.  However, with the newer color films as with the older
>versions, grain is not a factor considered in a color film, since the 
>latent
>image taken upon exposure, is replaced by chemical dyes during the
>development process.  (Reference any Kodak color film manual, or data
>sheet.)  The second problem to manipulating the image is, are you bringing
>out an image that you want to see or is it the image that is really there.
>If you read any book that deals with the conversion of an image from a
>photographic print or negative, or slide (positive), you  expose so that 
>you
>do not expose for the same periods of time that you would if you were just
>after a photographic print.  Sure you can push or pull an image.  But you
>lose imformation.  So how sure are we that the image that you manipulate is
>what was actually there?  Not very sure at all, if you were to study what
>the professional astronomers are saying.  Even they post raw images plus 
>the
>processed image, but they are very seldom manipulating the color.  R. 
>Warren
>
>
>>From: Mike Linnolt <mlinnolt@alum.mitdot edu>
>>Reply-To: meteorobs@atmob.org
>>To: meteorobs@atmob.org
>>Subject: Re: (meteorobs) OT:  Film for comet photos
>>Date: Mon, 09 Jul 2001 19:24:45 -1000
>>
>>Regarding color balance, this may have been an issue in the past,
>>but these days with most photos prepared in digital form for posting
>>on websites and so on, the overall color balance of a particular film
>>is largely irrelevant. Most image processing application, like
>>Photoshop for instance, allows you to adjust the various color
>>levels to achieve basically a perfect balance from any raw image,
>>as well as enhance every subtle detail.
>>
>>The real issue is to choose a film with very fine grain, high
>>resolution and good reciprocity characteristics. One such film is
>>Kodak Royal Gold 200. The 400 speed version is grainier, but still
>>can be enhanced to yield a decent image. You can see my result
>>with this film of the Comet LINEAR at:
>>
>>http://www.qsldot net/ah6l/A2_image.html
>>
>>Its a 5min exposure with normal 50mm lens and shows about 8° of
>>tail after processing in Photoshop. The raw image is pretty cruddy,
>>I can email it to anyone interested in the comparison!
>>
>>Mike Linnolt
>>Hawaiian Astronomical Society
>>
>>
>>On 9 Jul 2001, at 23:37, C.L. Hall wrote:
>>
>> > >What is the high speed tungsten film that you use???
>> >
>> > Kodak Ektachrome 320T.
>> >
>> > It's a colour slide film, balanced for tungsten light as opposed to
>> > daylight.  It is not recommended for meteor work - most meteor work
>>tends
>> > to be black and white.  It is also not recommended for comet shots if
>>you
>> > want what people accept as realistic colour.
>> >
>> > Tungsten film is great for copying prints.   Having some in the fridge 
>>a
>> > number of years back, I decided to try it for astro shots, and found
>>that
>> > it tends to work very well for comets.  If you are near a city, it
>>changes
>> > the sky tones to blue, and eliminates the awful green and brown skies 
>>of
>> > light polluted areas.  It tones down moonlight.  It brings out comet
>>tails
>> > very nicely, and will pick up tail in situations where daylight films
>>have
>> > problems.  The tungsten film is also much more forgiving as regards sky
>> > fogging.  With that said, for major comets I will run a number of types
>>of
>> > film, both daylight and tungsten balanced.
>> >
>> > I don't use filters.  I just enjoy pushing the limits of obscure types
>>of
>> > film - and comets are one of my favorite subjects.
>> >
>> > Clear skies,
>> > - Cathy Hall
>> >    south of Ottawa, Canada
>>
>>To stop getting email from the 'meteorobs' list, use the Web form at:
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>
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