Depth of field and aperture

Phall82

Phall82

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Colin
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Hi

I took some photos at my daughters christening last weekend in low light and used my Sigma 30mm f/1.4.

Due to the low light I used wide apertures but when I've looked at the photos afterwards the depth of field was too shallow and some people/parts of people are not sharp.

I prefer not using a flash where I can.

I understand the principles of aperture and depth of field but my question is, what aperture do people use in this kind of situation, such as weddings etc to get a nice blur but to keep faces sharp enough?

Also do you use the same aperture for lower light situations at weddings/parties?

Thanks

Colin
 
It's about practice really. Get to know how your kit behaves with certain settings, and you'll be able to judge how much dof you'll get. If you want a widish shot at the christening with everyone sharp, set a smaller aperture. This will need a lower shutter speed or higher ISO or both. A tight shot of the baby will probably concentrate on the eyes, so a narrow dof - wide aperture - is needed, with subsequent higher shutter/lower ISO. Practising in manual is probably the best way to learn.
 
If you shoot in low light and don't want to use flash, then you usually have only two choices. The shutter speed will generally be fixed at a longest premissable level to eliminate camera shake anyway, so that leaves you with either ramping up the ISO to deliver the right exposure and so increasing noise, or using a low f/number with the inevitable consequence of shallow DoF.

If you opt for the latter, your best chance is to try and get everyone in a line so that they're all covered by the small zone of DoF. That's tricky of course, but you can sometimes make it work by splitting people into couples that are easier to manage. That kind of thing, and try to make a virtue out of the shallow DoF with careful focusing on the most important area, usually the eyes.
 
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If you have to use a wide aperture and you aren't happy with the DoF you could try backing up a bit and increasing your camera to subject distance. This will give you more DoF but the downside is that your subject will be smaller in the frame. It'll be a different shot, but it might be a shot that you're happier with.
 
You need to have in your head the DOF for a given lens at a given F number at a couple of key distances.

I use a 85mm f1.4 on my 5D2 a lot and I know that at f1.4 at 2m I get about 5cm and it doubles every 2 stops. I also know that it goes up with the square of distance so at 4m I get 2^(4/2) = 4 times as much so 20cm.

So if I want to get 20cm at 2m I need 4 stops on f1.4 which is f5.6.

It helps that I find maths comfortable. But all of this can be on a laminated crib card.

In your position you could have upped the ISO speed and accepted a bit more noise in return for pictures with a better DOF.

Also if you are using the built in camera flash then beg/borrow/steal a speedlight and play with bounced flash it can produce really good results if used sensibly.
 
I you have a smart phone then get a DOF app, if not I think you can download a table from the Net, I will look for one.
 
Very useful. I'll look into that.

I'm pretty good with numbers myself so I'll think of it that way. I've got a speedlight but I just prefer the look of photos without flash when I can help it.
 
I have a great app on android phones called dof calculator
 
phall82
Apart from dof issues, how do you rate the lens, especially the sharpness at f1.4?
 
It's surprising how much light you actually need inside, to get a high enough shutter speed, i helped shoot a wedding and 1000iso wasn't enough even though it looked fairly bright, keep your focal lengths as short as you can while getting close.
 
ashaz said:
phall82
Apart from dof issues, how do you rate the lens, especially the sharpness at f1.4?
Click to expand...

Sharpness wise the lens is pretty good. The thing that impresses me the most is the overall look of the photos.

To be honest I've only tried it in low lights/indoor situations so far because I've only had it a few weeks but I'm impressed. It's become my favourite lens that I own.
 
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