Kodak Ektar 100's performance at Long Exposures
I'm going to be doing some evening/night shots in Brampton tonight, and I was thinking of using the new Ektar. Does anyone know how it performs with long exposures, and if it should be overexposed at EI 64?
I ran a quick test for reciprocity using a 120 second exposure with a 10 stop ND filter, but it was the end of the roll, so I didn't have room for proper bracketing. My estimated speed loss was about 1.3 stops. That would yield the following adjusted times in seconds.
metered time -- adjusted time
1 ----------------- 1.4
2 ----------------- 2.9
4 ----------------- 6.3
8 ----------------- 14.1
15 ----------------- 29.7
30 ----------------- 68.4
60 ----------------- 159.0
90 ----------------- 261.2
120 ----------------- 371.7
240 ----------------- 871.5
This test is a standard procedure for astrophotography film evaluation.
I'll see how badly the formatting breaks.
Oh, there also seems to be a slight cyan shift, but easily recoverable in printing, and without any egregious color crossover.
Last edited by Lee L; 12-14-2008 at 01:12 PM. Click to view previous post history.
Reason: bad parenthesis in spreadsheet for originally posted calculations
Thanks, Lee. I'll see what happens tonight.
How were your results? I'm thinking of testing myself.
Originally Posted by Shelley-Ann
I finally got around to testing Kodak's new Ektar 100 color negative film.
My test incorporated a 50mm lens set at f/2.8 and a 30 minute exposure. I shot the darkest part of the sky, directly overhead in the constellation Cygnus. This area has enough hydrogen Alpha to test this films sensitivity to emission nebulae.
30 minutes is a long time for f/2.8, but this result is in line with other 100 speed films in the reciprocity category.
This image still shows a little green cast that was present in the original scan. I adjusted green levels to rid most of it, so it is possible to use this film for astrophotography.
I hope this satisfies any curiosity others may have about this film.
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Interesting test. Thanks for posting. Given the spectral response curve for Ektar 100, the green or cyan shift we've both noticed in long exposures, and the relative brightness of the North American Nebula, Pelican Nebula, and emission nebulae around gamma Cygni, I'd say it looks like the red response is failing more rapidly than the blue and green.
For f:2.8 and 30 minutes, it doesn't appear that Ektar 100 is an outstanding candidate for astrophotography. Usable, I guess, but not with the best of astrophotography films over the years.
Agreed, it is not the best, but useable at fast f-ratios. I normally shoot medium format at f/4 and 5.6 so this film would not be an option. I won't be stocking it next to my E200, E100S, and Centuria 400.
Originally Posted by Lee L
Next on the chopping block, Acros 100.........
I'll be interested in those results too. Never seen anyone try it, or report on it for astrophotography. Fuji's response curve shows that it drops like a rock above 525-530 nm, so it'll be interesting to see if low reciprocity makes up for poor response in H-alpha. I got some of Freestyle's Legacy Pro 100 (supposed Acros) to try last week. Maybe I'll point a few frames up at night.
Originally Posted by Nightfly
Nice pic, Nightfly. You must have been somewhere reeeealy dark! The only place I have ever seen a sky remotely like that was while camping on my last road trip, in Utah. Not a light anywhere for miles around. You had to look really hard to find any spots of truly black sky.
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
- Rob Tyner (1944 - 1991)
I shot it from my home in Maine. I usually shoot with E200.
Originally Posted by 2F/2F
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