DOF at night - Help

[HQP]

I am wondering what the best scenario is with this type of shot. I'm thinking that my DOF should have been more around F8 or more. These were at ISO 400, F4, 1/8 sec. Am I correct that to improve this shot the DOF should be higher? I'm also thinking I should have used a higher ISO to get that if that is the case. Any help is appreciated!

[Maureen Souza]

Did you use a tripod? You could try a higher DOF but I would decrease my ISO to 100 or 200. I really like the first photo, even like it a bit soft.

[HQP]

I did use a tripod but I was on a small, narrow wall to get the angle so it wasn't as stable as I would have liked.

[Robert_Lay]

How could depth of field even be an issue here? It is not an issue in my opinion. Let's all truck on over to the dof calculator (if I can just remember where that web site is) and see the numbers!

My guess is that depth of field issues become non-issues at anything past 100 feet at any of the apertures you are considering.

I don't see anything in either photo that is anywhere near enough to be of concern.

[kawter2]

dofmaster.com


i just guessed you shout around 30mm

if so, f4 subject distance of 100ft your DOF is 28'-infinity

[Robert_Lay]

That was a good guess. The DOF calculator configured for your 20D says that if you are shooting with your lens zoomed to no longer than 50 mm and you are focused at a distance of 100 ft, with an opening of f/8, the depth of field is from 35 ft to infinity. That pretty much covers your scene like a blanket.

The DOF calculator is at:
http://www.dofmaster.com/dofjs.html

[HQP]

I thought DOF may have been a cause for the softness of the x-mas lights. I guess it could have been my not so firm foundation.

[Robert_Lay]

I thought DOF may have been a cause for the softness of the x-mas lights. I guess it could have been my not so firm foundation.

Think about this:
A point source of light in a picture may look as if it is not nearly as bright as it is.

Guess why?

Here's a hint. If you smeared a little drop of grease over your lens, the little point of light would not look like a little point of light - it would look like a big blob that is a hundred times bigger than it does with a clean lens - but it would be a dim blob.

Go back to the question of why the point source of light looks bigger than it is, and consider that your lens does not have a little glob of grease on it, because you didn't put anything like that on there. However, consider that nevertheless, your lens is going to have enough forward scatter or flare that it will scatter a tiny point source of light into something a little bigger. Doesn't have to be much bigger - just a little bigger, to look like it's soft.

Bottom line, you can put it on a tripod and you can even hang a 50 # bag of rocks from the tripod to make it real stable. It won't help.

Tiny point sources of light do that, no matter what. Why do you think they always portray stars as having 6 points. Believe me - they don't have 6 points, but the aperture blades in you lens might have 6 blades. Go figure!

[HQP]

Thanks for the information! This has increased my knowledge and I really appreciate it.