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.

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

"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.
--
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Legal Assistance on the Web | spam and read later. email to philip@
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"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.

"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

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

In message ,
"Marvin Margoshes" wrote:

You can't do better than setting the focus at infinity.

Infinity drifts with temperature.
--


John P Sheehy

"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!

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