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Old Nov 21, 2009, 10:43 PM   #1
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Default D40 Newbie: Focus Issue

Just upgraded to a D40 after a lifetime of point'n'shoots. Love it. But just noticed a problem.

I was shooting in lowish light without flash (I was in a museum, which didn't allow flash photography). Camera was configured on "P" (per ken rockwell's recco). I held the camera steadily, I thought. I locked focus right on the subject. And I got off a good shot, I thought. Things looked great on the LCD. But then I got home and viewed on a computer, and they are both completely out of focus!

So one small question and one large one:

1. (small) Where did I go wrong in these shots? Just need a steadier hand?

2. (large)If shots look sharp on the LCD and they look out of focus later.....how do I EVER know what's in focus? If I'd known, I'd have reshot!




Last edited by jimbotron; Nov 22, 2009 at 9:45 AM.
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Old Nov 22, 2009, 11:14 AM   #2
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Your shutter speeds were way too slow for a hand held photos.

Those were taken at 1/4 second and 1/10 second respectfully.

The rule of thumb for a hand held camera is to make sure your shutter speeds are 1/focal length or faster (using the 35mm equivalent focal length for a dSLR with an APS-C size sensor).

Those were both taken at 34mm (which works out to the same angle of view you'd have using a 51mm lens on a 35mm camera). Note that camera shake is magnified as you zoom in more (which is why you need faster shutter speeds as focal lengths get longer).

So, you would have wanted to use shutter speeds of around 1/50 second or faster to prevent blur from camera shake for those photos with a hand held camera. IOW, your primary problem is blur from camera shake, not focus.

Those photos were both taken at ISO 200. If you would have used Auto ISO, the camera would have selected a higher ISO speed (or for best results, just set it higher yourself, keeping an eye on your shutter speeds and deciding on the best compromise between blur and noise levels). Note that each time you double the ISO speed, the camera can use shutter speeds twice as fast for the same aperture and lighting.

But, the downside of higher ISO speeds is increased noise. So, your best bet for those types of photos is to use a tripod.
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Old Nov 22, 2009, 12:13 PM   #3
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Wow, that's a lot of great stuff to chew on (and learn from).

Thanks for taking the time. It will be intimidating getting up to speed on this thing.

The light didn't seem SO low there....I was hoping not to run into ISO and shake issues. And I certainly can't bring a tripod everywhere with me. But c'est la vie....
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Old Nov 22, 2009, 12:49 PM   #4
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In the same lighting, I'd probably increase ISO speed to around ISO 800 (allowing shutter speeds 4 times as fast as you were getting with those photos), then make sure to lock focus with a half press of the shutter button, then smoothly squeeze it the rest of the way down, making sure to listen for the shutter to open and close before releasing it to reduce any potential for vibration induced blur. If you're going to do a lot of shooting in that type of lighting, you may want to consider a stabilized lens if a tripod or monopod is not practical. Just keep in mind that stabilization only helps with blur from camera shake, not from subject movement. So, it's more useful for stationary subjects in lower light when you can't use a flash.
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