mikeklensch
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What makes you think that the high lens speed will be more beneficial than a good tripod?
Is the mechanism which can be affixed to a tripod that will compensate for the earth's movement relative to the stars to expensive to consider?
I've also considered (but haven't yet tried), doing a double exposure of exactly the same composition over the course of two nights...
Well....bingo! Combination printing is an old and venerable practice continued to this day by Bruce Barnbaum among several prominent photographers. Especially considering the dark prints you'll be making, combining a sky print with a landscape of the same area should not be difficult. You wouldn't have to time anything except the exposure of each subject. Blending the two in the darkroom is just a matter of masking each part individually in successive exposures.
Good and inexpensive and fast don't go with wide angle lenses in any format.
I suggest the Ross 5 inch wide angle express f4 might fit all the above. It's fast for a wide angle and about as inexpensive as you can get. I don't know how good it is but Ross makes quality optics so I assume its a good lens.
Nearly all of the cheap ones, ex-Air Ministry, are uncoated. I have one, it is flare champion of the universe. Never seen anything like it. And its pretty clean.Good and inexpensive and fast don't go with wide angle lenses in any format.
I suggest the Ross 5 inch wide angle express f4 might fit all the above. It's fast for a wide angle and about as inexpensive as you can get. I don't know how good it is but Ross makes quality optics so I assume its a good lens.
Thanks John... but that still doesn't get me my first (and most critical exposure) of the aurora. And the aurora is usually "touching" the landscape... not just directly overhead in the sky. So I would still need to shoot the landscape with the sky/aurora in at least one of the exposures... and the lens has to be fast enough to record that exposure in less than 30 seconds. Sigh... just no easy answer in LF... but the combination printing would be great in another application!
Mike
Greetings all.
I'm new to this wonderful website and forum, and am looking forward to getting educated from the wealth of knowledge to be found here.
I'm interested in getting my feet wet with large format... either 4x5 or 6x12 panos using large format lenses (photoman cameras). I love doing night imaging, and I specilize in aurora photography. I know that large format lenses are slow compared to 35mm and medium format, and I need the fastest lenses I can find (without having to go into debt). Since I really wouldn't require either a shutter, camera movements or mulit-coatings, I was wondering about barrel lenses, and if there are any fast, wide angle ones out there on the cheap. And I was also wondering how usable they might be wide open... or if that would just greatly compromise image quality, (I'm especially concerned about coma with stars). So any advice/experiences you all might have would be greatly appreciated.
Many thanks,
Mike Klensch
I'm no astrophotographer, so correct me if I'm wrong, but wouldn't you have more on the order of 12 minutes or so before movement would become apparent with a 90mm lens? Or does the 30 second figure have to do with the aurora?
Welcome to APUG! All I can tell you about this subject is that I have a 6.5 inch f2.9 Ross Xpress barrel lens which delivers the image quality that I would expect of a good uncoated lens and seems to cover 4x5" quite well (although I've only used it in the studio, not at infinity). Not a very common lens, though!
Regards,
David
No... at 12 minutes, you would have very significant trailing. The amount of time you can expose is dependent on lens focal length (as you already deduced), but it's pretty short. The old formula for 35mm equipment (which until now, I had mostly used for astro-work) is 600, divided by the focal length, will give you the amount of time (in seconds) you can expose before stars stop looking like points, and start to noticibly tail. So for a 50mm normal lens (in the 35mm world), this would yield 12 seconds. So, this would be the same for a 150mm large format lens. For a 90mm large format lens, you would have about 20 seconds of exposure before you would notice trailing... could maybe push it to 25 seconds.
My personal experience shows this formular to be pretty darn accurate. Now there will be some variability depending on your latitude, and what part of the sky you're pointed at (the sky will "move" less when pointed north and more when pointed east and west), and because I'm at 60 degrees N. latitude, I can do a bit longer exposures than someone at the equator.
In addition, the aurora can really rip across the sky as well. So, just as with running water, the aurora will blur, and you'll loose all of the detail and definition if you expose too long... heck, sometimes 10 seconds is too long if the aurora is really moving.
Hope that helps,
Mike
Pentax 67 with the 45 mm lens (f2.8 I think) might work well for medium format.
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