If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
Manual focusing for moon picture
"Mick Sterbs" wrote in message ...
"Jeff Durham" wrote in message ... auto-focusing than I can do manually. Should I auto-focus to some object in the distance and then switch it to manual leaving the focus alone for a moon picture? Maybe an f/8 with a slightly longer exposure time? I don't think my exposure time was too slow thereby allowing the moon to move because I didn't see any blurring around the edge. Why not auto-focus on the moon itself? It's clear and bright enough. It is, but tiny miss makes a big difference. Best to use an view finder magnifier and stay manual. |
#12
|
|||
|
|||
Manual focusing for moon picture
Shooting the moon is very easy if you have the equipment. For a 35 mm film
camera you need a 2000 mm lens to fill the frame so use the framing factor for your camera to give you the size of the lens you will need to accomplish this. Next the moon is lit by the sun so the "sunny16" rule holds for this object. If you ISO is 100 set the shutter at 1/100 and aperture at f16 ... way to many moon shots are way over exposed. Use manual focus and set it at Infinity. If you and lock your mirror up so much the better as the biggest hurdle you will face is vibration from your camera. Grant |
#13
|
|||
|
|||
Manual focusing for moon picture
"Jeff Durham" writes:
I am very new to this camera and lens. Here is a dumb question. How do you set this lens to infinity? It is a Canon 300D with a Canon EF 75-300mm lens. I can crank the focus ring all of the way down, but things at a distance are not in focus. I have to back it off some to go back to focus. That is not a happenstance I'm familiar with. I've never had a lens that would rack out beyond infinity so that distant objects were not in focus. SNIP Grant Dixon points out another factor I didn't think of -- mirror slap. Although I've never had a problem with tripod mounted cameras being shaken by mirror slap, that is a nice thing to rule out in your situation. I do have that problem when using my camera with a telescope -- the whole system vibrates for quite a few seconds after the mirror goes up, and I must lock the mirror up to get a clear image. -- Philip Stripling | email to the replyto address is presumed Legal Assistance on the Web | spam and read later. email to philip@ http://www.PhilipStripling.com/ | my domain is read daily. |
#14
|
|||
|
|||
Manual focusing for moon picture
"Georgette Preddy" wrote in message om... Why not auto-focus on the moon itself? It's clear and bright enough. It is, but tiny miss makes a big difference. Best to use an view finder magnifier and stay manual. And of course we must all acknowledge sg10.3's vastly and demonstrably superior knowledge. |
#15
|
|||
|
|||
Manual focusing for moon picture
"Georgette Preddy" wrote in message om... "Jeff Durham" wrote in message . .. The one good picture showed a surprising amount of detail. Can we see it? Can we see yours? No. Except, of course, this feeble effort: http://www.pbase.com/image/23936372 |
#16
|
|||
|
|||
Manual focusing for moon picture
In message ,
"Grant Dixon" wrote: Shooting the moon is very easy if you have the equipment. For a 35 mm film camera you need a 2000 mm lens to fill the frame so use the framing factor for your camera to give you the size of the lens you will need to accomplish this. Next the moon is lit by the sun so the "sunny16" rule holds for this object. Not exactly. The light coming off of the moon gets diffused by the atmosphere, and since it is dark all around the moon, nothing gets diffused from outside to replace the loss. When the moon is high in the sky, sunny10 or sunny 11 is more like it; when the moon is low and has any orange or golden cast to it, it needs many stops more exposure. Also, with digital, low-contrast subjects benefit from being over-exposed a little, so long as no clipping of desireable highlights occur, and DOF and motion freezing are compromised. -- John P Sheehy |
#17
|
|||
|
|||
Manual focusing for moon picture
In message ,
"Marvin Margoshes" wrote: You can't do better than setting the focus at infinity. Infinity drifts with temperature. -- John P Sheehy |
#18
|
|||
|
|||
Manual focusing for moon picture
"Jeff Durham" wrote:
First of all, look smarter: avoid top posting! "Phil Stripling" wrote: I shoot 35mm slides, so I'm not sure how to make this formula work in digital: e = 600/fl where e is the exposure time in seconds and fl is the focal length of the lens. The field of view of a single pixel at the sensor's centre is ~u/f radians, where u = pixel size, f = focal length (in the same units). The Earth rotates at w = 7.292e-5 radians/second. Putting it together: t = (u/w)/f Drop in the numbers for the 10D/300D (u=7.8e-6): t = 107/f where f is in millimetres. Thats the time for a one-pixel smear for a fixed mount. You probably want a 10th of that though, so maybe: f = 11/f Or about a maximum exposure of ~1/30th at f=300mm. I am very new to this camera and lens. Here is a dumb question. How do you set this lens to infinity? Don't bother: just make the image look as sharp as you can. Whatever it takes. It is a Canon 300D with a Canon EF 75-300mm lens. I can crank the focus ring all of the way down, but things at a distance are not in focus. I have to back it off some to go back to focus. First of all, 300mm isn't really long enough. 0.5 degree Moon - 335 pixels (for a 10D/300D type camera with ~7.8um pixels). Stick a teleconverter on your lens. A decent target is to resolve the crater Bessel (look it up on the net). Through the viewfinder, I got the moon in reasonable focus. It is only when I went to look at the image on my computer that I could see that it was slightly out of focus. Even if the lens was in focus, atmospheric "seeing" is going to munge a large number of images you take. Try taking 10 or 50 images and pick the best. Stacking images is recommended. Indeed, it is highly instructive to "movie" a sequence of registered images to see just how _bad_ the seeing actually was. Do not shoot over local sources of heat (houses, whatnot). Wait for the Moon to be as high in the sky as it gets. The next problem is mirror-smack. Get the recently "released" hacks for the Digital Rebel and use the mirror lock-up function, or use a better mount (e.g. telescope), but preferably do both. Cable release is de rigeur! |
#19
|
|||
|
|||
Manual focusing for moon picture
Nice picture. That gives me something to compare against.
Jeff "Jim Townsend" wrote in message ... Jeff Durham wrote: I will give your suggestions a try. I am in full manual mode and using a tripod. I will also try the autofocus again. This could be just an overexposure situation. FWIW, you can mess with the exposure equation by changing the ISO, shutter speed and aperture. (Faster shutter speeds need larger apertures.. etc) Here's a shot I took handheld using my 10D with a Canon 100-300 USM lens: (22 Kb 800x600) It's cropped, but not resized. I did a slight contrast adjustment and added a touch of sharpening. Focal length : 300.0mm (35mm equivalent: 463mm) Exposure time: 0.008 s (1/125) Aperture : f/6.7 ISO equiv. : 200 http://members.shaw.ca/jamestownsend/300mm-moon.jpg |
|
Thread Tools | |
Display Modes | |
|
|