Depth of field

-Paul-

-Paul-

Suspended / Banned
Messages
1,401
Name
Paul.
Edit My Images
Yes
Just a quick question on depth of field.

If you focus on a certain point does your depth of field extend both in front of and behind it or just behind it?
thanks for your help.
 
Everything you need to know about depth of field in that DoFmaster link :thumbs:

Specifically on your question, there is always more depth of field behind the focused point than in front of it, though when you're very close like a flower portrait it is around 49/51. At more normal distances, like a small group of people, it is roughly 30/70 (hence the 'focus one third in' mantra) and for distant landscapes there is greatly more DoF behind.
 
KIPAX said:
I didn't know that.. Is that as in techinically or noticably ?

Always learning :)
Click to expand...

I cannot describe it better than Ansel Adams so here is what he said:-

"We can achieve critical focus for only one plane in front of the camera, and all objects in this plane will be sharp. In addition, there will be an area just in front of and behind this plane that will appear reasonably sharp (according to the standards of sharpness required for the particular photograph and the degree of enlargement of the negative). This total region of adequate focus represents the depth of field".

Basically DoF is the noticably sharp area and the particular plane, or spot, the lens is focussed on is the only bit that is technically sharp.
 
KIPAX said:
I didn't know that.. Is that as in techinically or noticably ?

Always learning :)
Click to expand...

It is a fact of physics that there is always more DoF behind the focused point.

At macro range, it is virtually 50/50, somewhere around 30/70 for general stuff, but for distant landscapes it is anything up to 1:several billion (assuming the sun and moon are in shot ;)).
 
HoppyUK said:
It is a fact of physics that there is always more DoF behind the focused point.

At macro range, it is virtually 50/50, somewhere around 30/70 for general stuff, but for distant landscapes it is anything up to 1:several billion (assuming the sun and moon are in shot ;)).
Click to expand...

In BASIC terms? niticable? would you make a conciouse note that the DOF will be more behind when taking a pic or its not worth it?
 
KIPAX said:
In BASIC terms? niticable? would you make a conciouse note that the DOF will be more behind when taking a pic or its not worth it?
Click to expand...

Yes.

If I'm shooting groups that are several rows deep, I wouldn't focus on the front row.

Most of my other shooting (people) makes it irrelevant, but for landscapes and still life I'd want to be aware.
 
KIPAX said:
I didn't know that.. Is that as in techinically or noticably ?

Always learning :)
Click to expand...

Just looking at the Dofmaster link, and putting say a 300mm on a 1DX and focusing at 100 feet and the depth of field is split 49/51 at f2.8, with a depth of field of 5.7 feet. And at f16 it's 42/58 split. So you probably wouldn't see that much of a difference at the wide apertures I imagine you commonly use. Use a wider lens, say a 50mm and the split at f1.8 is 46/54 when focused at 20 feet. Change that to f8, and the split 21/79. :eek: If I put a 50mm lens on my cropped D300S, and the split is 31/69 at f8 when focused at 20 feet.

It is a complex subject. :thinking: :lol: Sensor size, subject distance, focal length and aperture size all meshing together to varying depth of field splits. So the one third in front and two thirds depth of field in front of, and behind the subject I have been using may not be the best idea most of the time. :bonk:

Anyone with a smart phone can download an app to get it exact. I don't have a smart phone. :shake: :lol:
 
KIPAX said:
In BASIC terms? niticable? would you make a conciouse note that the DOF will be more behind when taking a pic or its not worth it?
Click to expand...

Yes, I'm always aware of how DoF changes and try to take it into account. For general stuff I work on the one-third-in rule of thumb but it is far from an absolute, as Redhead explained. Another way of putting what he said is the more DoF you've got, the more bias shifts behind.

One particular area where one-third-in doesn't work is landscapes. People often say focus one-third up the frame or one-third-in but that never works optimally and will usually lose a lot of potential foreground sharpness (and IMHO, OOF foreground subjects usually don't look good). Need hyperfocal distance focusing for that. I have a few key numbers stuck inside the lens cap - all you need really ;).
 
DOF Master is a nice link, thank you for sharing it here.
 
You must log in or register to reply here.
Back
Top