Re: Canon's new astrophoto DSLR announced [ 4x5" FILM option? ]

On Sat, 04 Jun 2005 16:50:37 GMT, Ralph Hertle
<ralph.hertle@xxxxxxxxxxx> wrote:

>What I find confusing is the trend towards smaller image planes.

In the digital world, the trend is definitely towards larger sensors.
The Canon 10D/20D family is already at around 60% of a 35mm frame, and
the higher end cameras are at 35mm. I expect the next generation of
DSLRs will have full frame sensors. Those devices already have higher
resolution than 35mm film; how high things ultimately go will depend on
the market. My guess is that prosumer will stop at 35mm full frame,
because it is very, very good and more than enough resolution for most.
Larger format sensors will probably show up in very expensive,
specialized equipment- rather like the large format film market now.


>I would ask why there hasn't been a large film format option for
>telescopes?

There are almost no amateur scale telescopes that can come close to
illuminating a 4x5 plate! The majority of scopes are pushing it with
35mm sensors. Certainly, some people have done medium format with higher
quality scopes, though. But in the end, I think that fewer and fewer
people want to fool around with film. It is lower resolution than
digital sensors, far lower dynamic range, far lower sensitivity.
Basically, too much work for too little gain.

>Then you can scan the film image on a 12,000 dpi scanner to the
>create a digital image.

But that is silly, because there isn't close to 12,000 dpi of
information on the film to begin with. The large format film doesn't
have any better resolution than small format film- around 10-15um
(bigger than the Airy disk of an f/5 scope). So all the bigger format
lets you do is go to a wider FOV. How wide do you need to get?


>The type of balanced spectrum color that used to be offered in 4x5" and
>8x10" Polaroid film was spectacular. Isn't that still a valid and low cost
>option?

But color film produces horrible color compared with tricolor imaging
(which is what many of the last generation of film imagers were doing
before they switched to digital). And color films are not generally
"fine grain". (Indeed, fine grain films suitable for astrophotography
seem to be going away.)

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
.

Relevant Pages

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