Re: [APML] IDAS LPS Exposure Question and Problem

[John Laborde <jlaborde@ix.netcom.com>]

Title:

Gary,

I use Lumicon's Deep Sky filter which is similar to Hutech's IDAS filter.
I need to expose for 90 min to get the same red density as a 50 min exposure
without the filter at f5. My guess is you need to go 90 to 100 min at f/5.6.
Provia is not as good in the red as E200. You might want to use E200 for
red objects such as the North American Neb. Your prime focus images look
more like focal plane tilt than film buckle.

John Laborde

GARY HATFIELD wrote:

Hello All,

    I've done 2 exposure tests with my new filter, 20, 30, and now the latest of 45 min. using my 105mm lens.  The 20 & 30 min. exposures were very dark so I upped the time to 45 min. and it's still too dark.  I know several of you use this filter and was hoping someone could tell me how much you had to extend your exposures to acquire close to the same density on the slide?  Also, is this magenta cast normal with this filter?  I have uploaded with/without examples to give you an idea of how they look.  These are raw scans with no corrections in prescan or after.  All exposures were using Fuji Provia 400F pushed 1 stop.

 

   My problem you can see in the 2 top images taken at PF.  Stars on the left side are out of focus while the stars on the right look ok.  Is this the film not laying flat in the camera back or does it look like something with my optics?  If it is the former, what is a good way to correct this?

 

http://www.starryestateobservatory.com/My_Homepage_Files/Page109.html

 

I'd really appreciate any ideas or suggestions I can get here.

 

Gary

 

 

 

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