inbigd wrote:
Hello
I have a d3200 and I'm trying to take pics of the full moon using a 600mm Sigma mirror lens. I've tried ISO 100, 1/125 and higher ISOs - 200, 400 but image is still out of focus.
I'm sure that I need to get a tripod also but my question is - should I be able to get a good image with the cropped sensor ,this lens and a tripod (once I get one)?
thanks
You say you're trying to take a shot of the full moon, hand held, with a D 3200 (APS-C sensor ), with a mirror lens, and your pictures aren't "sharp", and will a tripod help?
The short answer I'm afraid, is "not much"; I'll try to explain a few things to you.....(lots of factors happening here )
#1. Because your camera has a less-than full size sensor, any lens that you attach to it will have an effective 1.5X "crop factor"; in other words, any 600 mm lens "magnifies", (makes things appear to be ) 10 times closer (bigger ) on a full-frame camera; with a APS-C (less than full frame ) sensor, 1.5 X 10= 15X.
Have you ever tried to look through a set of 15X binoculars, hand held? (or even 10X for that matter ); if you haven't, don't bother, as you won't be able to see ANYTHING, because hand-holding binoculars, (and cameras ), results in a LOT of shaking, and jiggling around, and in the case of your set-up, it's "shaking around" 15 times as much as it would appear to your "un-aided" human eye balls.
#2. Mirror lenses; without going into a long, drawn-out explanation of optics, I can tell you this; astronomical telescopes have been using the same optical principal as a "mirror lens" for years and years now, for all sorts of very good reasons; along the way, "someone" had the idea that they could use the same "principle" to make a "relatively inexpensive" camera lens; there have even been mirror (or "reflex" ) lenses that cost a considerable sum of money; like all "well-intentioned" but "impractical" ideas, mirror lens never "caught on" and all or the major camera makers quit making them years ago. None have any means of adjusting the aperture being one big problem, plus mirror lenses, (unlike ordinary "refractive" lenses ), correct for NOTHING; (astigmatism, coma, barrel distortion, chromatic aberration, pin cussion, nothing )
Now; look in any astronomy magazine and you'll see dozens of telescope makers offering astronomical telescopes with names like "Schmidt-Cassegrain" and "Maksutov", and "catadioptric" etc etc etc and they all do a superb job of making astronomical images. I rather think that must be why so many people seem to think that mirror lenses would be great for camera lenses, when in actual fact, they make exceedingly POOR camera lenses, for MANY reasons. Listing all of the reasons would result in a VERY long post;
#3. The Full Moon; The full moon is a very poor photographic subject usually, and for many reasons; it gets better when made with a sophisticated, computer-driven astronomical telescope, but not all that much better, mainly because it has no contrast but a LOT of brightness, simply because of the way it's reflecting direct sunlight.
If you happen to be someplace where it's perfectly flat, (like out at sea ) look at the "horizon"; then look at "the zenith" (straight up ); from the horizon to the zenith is 90 degrees "of arc"; now, when the moon is full, it subtends an angular distance of app. 1/2 of a degree of arc; (or about 1/180 th of the distance between the horizon and straight up;) Remember......this is with the naked (or "unaided" ) eye; Now.....if you try to photograph the rising full moon with say, a 600mm lens, and a less than full frame sensor, you're not only "magnifying" it's angular diameter 15 times, you're also "magnifying" it's "movement" 15 times also! Which is why
shots taken of the full moon (or the sun ) must be fairly short exposures; but when you do the same thing with a equatorially mounted and computer driven telescope, this is no longer a problem because the telescope is "driven" to match the earth's rotation, which causes the "subject" (full moon ) to appear to be "standing still" while the exposure is made. (And even then, the very bright full moon is a very poor subject. )
Spend some time looking at some great photography in any really good magazine, (such as Nat Geo ); you will rarely see shots that were made at 12:00 noon, for the very same reason; the lighting is BRIGHT, and it's coming from such an angle that there are no shadows, therefore everything looks "flat" (and "uninteresting" ); exactly like the bright light from a camera mounted speed-light results in "flat light"; almost all subjects look more interesting when shot early am, or late pm; with the moon, the "better shots" are when the moon's phase is first quarter or third quarter.
Also, you're getting "out of focus" mixed up with a "shaky camera" due to lack of stability. Focusing on anything that's app. 250,000 miles distant is easy! just set the lens on "infinity"