Re: [APML] More scanning questions

[Jerry Lodriguss <jerry@astropix.com>]

Hi Steve,

Yes, the E200, even pushed, should have less grain than the LE400.  The 
LE400 was fairly grainy to start with.

The other thing that affects apparent grain is where you find it in 
transparency vs neg film.    In neg, the grain is mostly visible in the 
shadow areas. Underexposing neg film and then scanning and processing for 
shadow detail makes it worse. Overexposing most negative films actually 
makes the grain finer.

Some neg films use a mix of grain sizes, with the larger ones naturally 
being more sensitive to light (more surface area to collect photons). An 
underexposed image will only expose the larger grains, making it more 
grainy in the final scan.

If you underexpose transparency film, you don't get anything, just the 
maximum density of the film. Of course, shadow detail that is just above 
the d-max of the film is extremely difficult to scan, which is why it is 
advised to expose transparency film for astrophotos so there is 
considerable sky-fog density over the d-max.

So, in both cases (neg and trans), there are good arguments for erring on 
the overexposure side, if you are going to err.

Jerry


>Last night I scanned images taken over last weekend using E200 pushed 1
>stop, and
>hypered RG200 and LE400 film. The LE400 looked much more grainy than the
>other 2
>films--so much so I even tried  flipping it over and scanning the other
>side thinking I had
>scanned the wrong surface. The result didn't look significantly different.
>
>Is this normal? And should I expect LE400 to be noticeably more grainy than
>the E200
>pushed one stop?
>
>Of the 3, the RG200 seemed the least grainy.


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