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Shooting to infinity


pearly 14 23
15 Dec 2005 1:21PM
Hi,
I have seen a number of images that photographers have shot to 'infinity' and the images end up very sharp. Does anyone know how this technique works and when best to use it? I currently use a canon 350d.

thanks

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strawman 16 22.1k 16 United Kingdom
15 Dec 2005 1:46PM
Sorry not heard of the term but is that another way of saying they use hyperfocal techniques. If you mean there are a lot of things close and far away that are in sharp focus then the technique is to stop the lens down to get a large depth of field.

If I have the correct topic then [link=dfleming.ameranet.com/custom.html] this web site [/link] has lots of facts and a calculator to help you.

To do this you need a good tripod, and think about using the self timer or a remote cable to trigger the shutter. A rule of thumb for a fairly wide lens is to manually focus it about a third of the way between you and a far away point and set a small aperture, say f16. But read the articles in the site I linked to and you can get the calculator if you wish precision.
User_Removed 17 2.8k 11 United Kingdom
15 Dec 2005 2:14PM
Never heard of 'Infinity'?
sillyconguru 15 4.4k
15 Dec 2005 2:16PM
I would think that John means he has never heard the term "shot to infinity", as neither have I.
strawman 16 22.1k 16 United Kingdom
15 Dec 2005 3:08PM
Thanks Laurel. I did a quick check with my sons encyclopedia and it appears to be a car brand in America, and a place that Mr Buz Lightyear passes on a regular basis. I can see I am a long way from the correct definition.

I wonder if Mr Lightyears phrase is prompted by the confusion over how to correctly calculate DOF to 10 decimal places.

Sadly I must confess Andrew has correctly interpreted my posting.

So what is shooting to infinity?
16 Dec 2005 12:58AM
From some of the reading I've done lately "shooting to infinity" means exposing for subjects at various distances up to the horizon, supposedly good for sunsets etc... There's an infinity symbol (an 8 on it's side) on the aperture setting of my lens so I assume it means setting to that but I'm sure there's someone here who'll know more than me on this.
ahollowa 16 1.1k England
16 Dec 2005 1:01AM
If you focus on infinity then anything near will be out of focus wont it? I'm with John on the hyperfocal technique.

cheers

Al.
BruceC 14 171
16 Dec 2005 2:17AM
If the whole of your subject is at infinity, and there's nothing in the frame closer than infinity, you can focus on infinity without losing any sharpness. Otherwise you need to work out the hyperfocal distance (see earlier postings) and focus on that instead of infinity. This can be a pain with zoom lenses, because they don't have markings to show you the range of focus - prime lenses normally do.

If you focus on something at infinity and you have something in the foreground of the frame, the foreground may or may not appear sharp as well - it depends on the focal length of the lens (wide angles have more depth of field) and the aperture you're shooting at - the smaller the aperture (i.e the higher the f-number) the more depth of field. The trick is to make sure that you balance the focal length, the aperture, and the point of focus to get the result you want.

I sounds complicated, and I suppose it is - it requires practice, and a bit of study to get your head round it. It's particularly important for landscapers to get to grips with it, otherwise you will often get disappointing shots. With most (but not all) landscape shots the aim is to get front to back sharpness, so an understanding of this is critical - as is using manual focus rather than auto, using a tripod, and taking control of the aperture you use rather than allowing the camera to choose it for you.

Bruce
Kris_Dutson 17 8.2k 1 England
16 Dec 2005 2:27AM
With your 350D and a widish lens; F16 or above, focus one third into the scene and it's pin sharp front to back - sorted.

Kris.
BruceC 14 171
16 Dec 2005 3:02AM
The one third rule of thumb sometimes works, and sometimes doesn't. For example, using a 350D with 18mm lens at f16, according to this useful site the hyperfocal point is 3.56 feet, which will give acceptable sharpness from just under 3 feet to infinity. If you were to work out a third of the way into the scene (assuming your subject starts at your feet and goes to infinity), you'd be unlikely to focus as close as 3.56 feet away - my guess is you'd go for at least 10 feet, which would mean the foreground wouldn't be acceptably sharp. That may be fine for some subjects, but with others it could mess up the shot.

My experience is that with wide angles the hyperfocal point is usually closer than I expect it to be. All this sounds a bit nerdy, but if like me you've had shots that fail on this score, it's worth the effort. I knocked up a small spreadsheet covering the focal lengths and apertures I normally use, with data from one of these websites. It only takes a second to get exactly the right hyperfocal point, and then estimate how far away that is from the camera.

OK, you're right, I'm a nerd ...

Bruce
p-g 16 126 United Kingdom
16 Dec 2005 4:26AM
Interesting link. They do a Palm version but does anyone know if there's a Pocket PC version about? Now that would be cool.
Paul
mipettin 15 884 2 Scotland
16 Dec 2005 4:53AM
Paul

Try here - Pocket PC Goodies

Cheers

Martin
Westers 15 3.9k 1 Burkina Faso
16 Dec 2005 5:04AM
And here lies the achilles heel with hyperfocal focusing calculations...they use lots of precise data to work out the calculations but when it comes to putting it into practice it relies on estimation and guess work. Can you estimate 3.56m away from you? Neither can I.
andytvcams 17 10.4k 1 United Kingdom
16 Dec 2005 5:08AM
A good eye and plenty of practise Smile
strawman 16 22.1k 16 United Kingdom
16 Dec 2005 5:08AM
**Edit what Andy said with more words.

Of course the correct answer is you set your camera lens to 3.56 m and see what in the subject is the sharpest item, and is there anything closer that is not sharp.

And you can aproximately gauge the effect by stopping the lens down, and peering through the viewfinder.

But to be honest, it all come down to making judgements.

After becoming used to a range finder it is interesting how you can start to judge distances with reasonable sucess.

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