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09-16-2012, 10:35 AM   #46
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QuoteOriginally posted by c-meier Quote
Interesting. I have never done that kind of photography, so I don't have the experience, but always thought having a larger aperture was an ineffective way of getting more light from point sources like stars or meteors.
For astronomical photography, aperture is almost everything. Bigger diameter = more light capture. That's why astronomical telescopes are so immense = apertures measured in several meters.

09-16-2012, 10:57 AM   #47
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QuoteOriginally posted by WPRESTO Quote
That's why astronomical telescopes are so immense = apertures measured in several meters.
Makes sense, I guess. I just remember someone explaining the relationship between aperture and exposure being different for point sources. Maybe it is the absolute aperture that matters? (as opposed to the aperture relative to focal length)
Tried to look it up online, but can't find the info.
09-16-2012, 11:13 AM   #48
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QuoteOriginally posted by c-meier Quote
Interesting. I have never done that kind of photography, so I don't have the experience, but always thought having a larger aperture was an ineffective way of getting more light from point sources like stars or meteors.
Size matters in astrophotography
09-16-2012, 11:32 AM   #49
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If you're trying to capture stars and wide angle milky way shots, you don't really want to go above 30 seconds at 10mm on APS-C to avoid the earths rotation from blurring things. F/2.8 gives you much better results than f/4 as it allows you to keep the ISO down for the same exposure length.

09-16-2012, 11:49 AM   #50
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QuoteOriginally posted by Big G Quote
If you're trying to capture stars and wide angle milky way shots, you don't really want to go above 30 seconds at 10mm on APS-C to avoid the earths rotation from blurring things. F/2.8 gives you much better results than f/4 as it allows you to keep the ISO down for the same exposure length.
Add the O-GPS1 and you have an even better combination.
09-16-2012, 12:54 PM   #51
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QuoteOriginally posted by jogiba Quote
someone here posted a documentary of this guy who's like the best astro photographer in the world, he even had pentax gear, this huge setup in this little dome in his backyard... I'd look it up but kinda lazy right now...
09-16-2012, 02:46 PM   #52
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QuoteOriginally posted by traderdrew Quote
These are the abbreviations of this 10mm: ED AS UMC CS

And this is from the Samyang 14mm F/2.8: IF ED UMC

I didn't by the 14mm because it is prone to lens flare. I don't know if any of these abbreviations indicate some sort of multi-coating.
ED = Extra-low dispersion glass
AS = Aspheric lens
UMC = multi-coating
CS = ?
IF = Internal focusing (the lens's length doesn't change when changing focus distance)
09-16-2012, 04:14 PM   #53
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QuoteOriginally posted by traderdrew Quote
These are the abbreviations of this 10mm: ED AS UMC CS

And this is from the Samyang 14mm F/2.8: IF ED UMC

I didn't by the 14mm because it is prone to lens flare. I don't know if any of these abbreviations indicate some sort of multi-coating.
No offence but this type of statement is nothing more than misinformation. Every modern lenses have some sort of multi coating but every one of these multi coated lenses are prone to flare if you include a strong light source/reflection in your composition, it's just more prevalent with UWA lenses. All of my UWA lenses including Pentax, Sigma and Samyang are all susceptible to flare in above situation. Don't want any flare, simply shift your composition until the light source do not affect the shot or move the shooting position to have some object block the light source.

Pentax - SMC, Samyang - UMC Do you need it spelled any plainer than this?

09-16-2012, 04:51 PM   #54
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QuoteOriginally posted by excanonfd Quote
No offence but this type of statement is nothing more than misinformation. Every modern lenses have some sort of multi coating but every one of these multi coated lenses are prone to flare if you include a strong light source/reflection in your composition, it's just more prevalent with UWA lenses. All of my UWA lenses including Pentax, Sigma and Samyang are all susceptible to flare in above situation. Don't want any flare, simply shift your composition until the light source do not affect the shot or move the shooting position to have some object block the light source.

Pentax - SMC, Samyang - UMC Do you need it spelled any plainer than this?
Okay, no offence taken. I thought I read a review somewhere saying it was prone to lens flare unlike the Pentax 12-24. I'm still new to wide angle shots and lenses. I think I would rather have this lens than the 14mm since I have the 12-24
09-16-2012, 04:55 PM   #55
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QuoteOriginally posted by bmonki Quote
someone here posted a documentary of this guy who's like the best astro photographer in the world, he even had pentax gear, this huge setup in this little dome in his backyard... I'd look it up but kinda lazy right now...
A good place to learn a little about astrophotography, and to see some at times astounding astrophotos taken by amateurs in their backyard, is "Sky & Telescope" magazine, especially the "gallery" pictures at the back end of each issue. For star images, typically the telescope has an aperture of 8" or larger, but for planetary or lunar photography, scopes with objectives as small as 4" may be used. Most star/galaxy/nebula pictures are taken with reflectors; planetary/lunar often with refractors; and whole-sky commonly with regular camera lenses. Compared with telephoto lenses for cameras, astronomical refractors have extremely simple optical construction, typically only two or three lenses. For stars & planets tracking is pretty much a necessity, but to get around the inevitable imprecision of equatorial mounts during long exposures (30 minutes is not unusual for stars), almost all serious astrophotographers use image stacking = numerous short exposures combined.

Apologies if I'm posting very basic information already known to many if not most Pentaxians.
09-16-2012, 08:13 PM   #56
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QuoteOriginally posted by Docrwm Quote
No, I think they mean degrees of angle of view.

Images added.
Wider than the 8mm-16mm Sigma?. If it was wider, wouldn't it be 7mm?
09-16-2012, 08:16 PM   #57
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QuoteOriginally posted by traderdrew Quote
Okay, no offence taken. I thought I read a review somewhere saying it was prone to lens flare unlike the Pentax 12-24. I'm still new to wide angle shots and lenses. I think I would rather have this lens than the 14mm since I have the 12-24
Yes and no. More elements means more points of flare, and more possibility of reflection between the elements. Primes generally have less elements than zooms.

IMO, UWA primes blow. Anything that wide you want the ability to zoom some, and zooming with your feet on an UWA doesn't usually work.
09-16-2012, 08:18 PM   #58
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Oh, it's F2.8... that makes it more interesting; especially for indoor photography. For landscapes... meh.
09-17-2012, 01:14 AM   #59
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QuoteOriginally posted by Mistral75 Quote
CS = ?
I believe it means Cropped Sensor. At least that's what the first sentence in the description of the Samyang 8mm f/3.5 Asph IF MC Fisheye CS would lead me to believe. "The Samyang 8mm f/3.5 Aspherical IF MC Fisheye Lens is a high quality Fisheye type ultra wide angle lens for digital SLRS / DSLRS with an APS-C size Cropped Sensor (CS)."
09-17-2012, 01:46 AM   #60
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QuoteOriginally posted by meeverett Quote
I believe it means Cropped Sensor. At least that's what the first sentence in the description of the Samyang 8mm f/3.5 Asph IF MC Fisheye CS would lead me to believe. "The Samyang 8mm f/3.5 Aspherical IF MC Fisheye Lens is a high quality Fisheye type ultra wide angle lens for digital SLRS / DSLRS with an APS-C size Cropped Sensor (CS)."
Sounds reasonable. Thank you for your answer.
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