This is where the smaller size of the focusing sensors of cameras like the Nikon D3 and Canon 1D series is useful. other than that, no real advice but to zoom in on the images every now and then to confirm you’re nailing it. Shoot a lot and then pick the best in post.

Neil vN

What is the trick to get focus on the eyes when people are wearing glasses? The AF always seems to catch the glasses and not the eyes when using shallow DoF.

…yes, that is what I was trying to ask.
I’ve noticed that I got many keepers at f/2.0 with 50mm 1.8 on 40D while some people (FF users I suppose) seem to avoid it during opportune moments in the church.

Polarbear .. thank you for the great feedback.

The broad categories for the aperture ranges was with 35mm / full-frame digital in mind.
It would be different for the 1.5 and 1.6 crop sensors, and I would say roughly a stop difference in Depth Of Field.

I wouldn’t put strict numerical values on this though, since the entire motive behind this post was to think in broad terms about the effect we want, without getting locked into a specific consideration about why f3.5 .. or any other specific number.

With a crop-sensor camera, (eg 1.5x crop), you do need to step back to get the same framing of your subject. Hence .. 75mm on a full-frame camera, will give you the same framing of your subject as 50mm when you step back. And it is at this point usually where war is waged on the photography forums about the specific terminology.

Re your question 2 .. I’m not sure I follow you. Are you asking whether you have more apparent Depth of Field when using a specific lens .. when you compare full-frame to crop sensor?

Neil vN

.

[b]“I decide on depth of field by grouping my needs into three categories ..
- shallow depth of field (f1.4 to f2.8 .. or even f4)
- medium depth of field (around f4 – f8)
- lots of depth of field (f8 and deeper)”[/b]

I tell you, those categories made no sense to me when I first read this article (I use APS-C sensor camera). I was surprised to see f4 being categorized as “shallow”.
It appears that the DoF attained using a lens at f/4.5 on a full frame sensor camera, one would need to use an aperture of roughly f/2.8 on a camera with a 1.6X crop factor to reproduce the same DoF (using the same lens).

Question 1:
I suppose camera distance to the subject will be longer when using APS-C camera or is it assumed to be the same as for FF?
(SOURCE: http://www.cambridgeincolour.com/tutorials/lens-quality-mtf-resolution.htm)

.

So, medium depth of field:
f4.0 – 8.0 (FF sensor camera)
f2.5 – 5.0 (APS-C sensor camera)

Had I not known this, (though with some doubt) I was going to try f5.6 on a group portrait. In one of these articles, Neil referred f3.2 as being shallow; I understand now how that would be so.

Question 2:
While using 50mm 1.4 @ f1.8 on FF one may need to be careful so as not to mis-focus at an opportune moment, is it safe of me not to worry much when applying the same setting when using it on APS-C sensor camera? (Let’s assume that the light condition is favorable)

Thank you Neil!

Enrico … more or less. But it is also not something one should get too academic about. This is more a guide to how I think in terms of depth-of-field … as opposed to the absolute method of using DoF calculators.

Neil vN

Thank you again.
Enrico

Shoot a lot. And refocus. And shoot. A lot.

Neil vN