FOCUSING PROBLEM

[queenbee288]

Hey guys, my nifty fifty (50mm 1.8 II) came yesterday. I bought it slightly used ebay. I am a newbie so the problem could be with me. I took over 100 pictures and I was unable to get a single keeper. I cant figure out what the problem is. I understand it is supposed to be sharp stopped down ( I shot in AV at 1.8 Only the head is in focus if that is what i focused on, everything else out of focus. I do understand this is depth of field. So to get less depth of field I up the aperture, right? when I do that everything is soft, not exactly out of focus but very soft. I read that this is a great low light lens. i thought I would be able to take pics of my pets indoors without flash to avoid demon eyes. NO! I have gone through so many aperture, shutterspeed, iso combos trying to find one that works. Am I missing something obvious here? By the way, still soft with flash also but a little better.

[KevC]

The wider the aperature, the narrower the DOF and the softer the lens will be.

Stop it down a coupla stops (it's beautifully sharp at f/4) and bump up the ISO if you want sharp images at low light. @ f/1.8 it'll be very soft, and I believe the 'problem' you are describing is the narrow DOF.

[queenbee288]

I know that there is a narrow depth of field. Does that mean for instance that I can't take a picture of my dog and have more than her face in focus? I thought that if I changed the aperture my depth of field would be less narrow.

[steven]

Please don't take the badly but I think you are thinking that little number in apature mean little apature.
It is just the reverse.
1.8 is the aerature wide open and bigger numbers are smaller aperature.

[queenbee288]

I know that and I am not offended, I appreciate you trying to help a newbie. I knw that it is opposite but I guess I just misunderstood the term "stop it down" but anyway, I came home today and worked with it some more and it is fine. Like you said sharp at 4. I think that last night it was just darker than I realize and there seems to be a big difference in indoors daytime and indoors night. I went thru the whole sequence last night. I also cleaned the lens when I came home and maybe that made the difference. Thank You. Char

[Persian-Rice]

The nifty-fifty has an exteremely shallow DOF at 1.8. It's so shallow that if I take a picture of you and focus on your nose, your eyes will be out of focus.

[Belmondo]

according to this calulcator,
http://www.dofmaster.com/dofjs.html
The 50mm at f/1.8 would have a DOF of roughly 1 3/4 inches at four feet. the 1.4 would have a DOF of just a little over an inch when wide open
Either one is pretty tight.

[queenbee288]

Thanks for the tips.

[queenbee288]

Hey Guys, I think I got that focusing DOF thing figured out. See this photo.

http://community.webshots.com/scripts/editPhotos.fcgi?action=showMyPhoto&albumID=126005174&photoID=272562408&security=KVztbo

[Belmondo]

Apparently...

When I go to your link, I get this:


An error has occurred.

You do not appear to be the owner of this album.
Make sure you are logged in.

Please push the Back button on your browser to correct this problem.
Thank you.

It is very clear nad in focus, though. ;)

[DocFrankenstein]

The more DOF you want, the more light you need. If you are shooting with 50/1.4 for example. At f/1.4 it lets in 64 times more light than at f/11... But f/11 would give you nice depth of field to work with.

This is why studio photographers shell out for those high power 500$ light cannons.

Most of the non-studio photography is about a good compromise between shutter speed, ISO and aperture. You need to find your own compromise and the image quality will always be less than ideal, because you're not in control of all variables. IE light and the speed of the subject.

[HKFEVER]

according to this calulcator,
http://www.dofmaster.com/dofjs.html
The 50mm at f/1.8 would have a DOF of roughly 1 3/4 inches at four feet. the 1.4 would have a DOF of just a little over an inch when wide open
Either one is pretty tight.

How about 85mm f/1.2L 's DOF in 5 feet?

[Belmondo]

That calculator doesn't have f/1.2 on it, but it does have f/1.0 and f/1.4.

The DOF for the 1.0 is .04 ft (about half an inch), and the 1.4 is .05 feet (about .6 inches). Somewhere in that range.