D.O.F? "Infront of focus point" vs "behind focus point"

[johnmsanderson]

Really like that example Praslowicz.

[K. Praslowicz]

Really like that example Praslowicz.

Thanks.

[mandonbossi]

Hi everyone, Sorry about the delay in responding, was down the coast for a bit without internet access... Thanks so much to everyone for sharing their thoughts and good to see it has raised some healthy discussion... Thanks to K. Praslowicz for sharing that photo as well, it is great and yes, it is somewhat the look I am going for.. I do really like it when things get really, really shallow and forgot to link to some of Richard Renaldi's work as an example of this...

I especially like it when it is quite evironmental and the figure is fairly small but the background is really quite out of focus... Something I think you can only really achieve with 8x10 and to a lesser extent a fast 5x4..

I am still a little confused as to the rule of D.O.F. It seems that the general rule is that the latter 2/3 in an image are generally sharper than the first 1/3, hence the rule of focusing 1/3 in (for landscapes for example). In these examples, it seems to me that sharp focus is kept better in front of the focal plane (assuming that the camera is levelled, no tilts etc etc).

This has also been my experience in shooting with the Xenotar at anywhere from f2.8 to f4...

Does anyone else see this? If so, doesn't this contradict the general rule?

Apologies if I am missing something really obvious here, it is possible..

Any thoughts or suggestions are once again always appreciated!

Cheers Mandon

P.S Thanks to whoever linked to Greg Millers work, awesome stuff! Although I think by looking at his, he is getting really creative and manipulating the plane of focus for a lot of his shots... Which opens up a whole different discussion..

[mandonbossi]

One more... In this example, it seams to my eye there is a sharp area in front of the subject but it seems to fall off very quickly behind him.. I know it is a bit hard to see with such small images but I have one of his books and it does show this effect a lot better..

OK, thanks again.

Mandon

[cowanw]

I think the 1/3 2/3 rule is
accurate for shots where the subject is positioned at 1/3 of the hyperfocal distance
or is
for shots with Infinity in focus and the horizon high up on your GG: focus 1/3 of the way up the GG.
These are 2 different rules

[K. Praslowicz]

Apologies if I am missing something really obvious here, it is possible..

I think this is the obvious point being missed. In my experience regarding large format, getting everything in sharp focus is difficult. Not trying to squeeze every last bit of DOF out of a lens isn't. You might very well be over thinking this.

http://www.youtube.com/watch?v=SwEAxrmBz64 There is a line in that video where he says the first thing he does is focus on the eyes. I would not be surprised one bit if he puts most of his effort on composing the scene and working with the sitters, then just focuses on the eyes and shoots at a moderate f-stop, and the 8x10 format does the rest.

[aduncanson]

Please look at the two graphs attached below representing calculated data and please do not overlook that the two charts have very different horizontal and vertical scales.

These are an attempt to answer the question of how de-focus of the image changes with object distance, So (that is S sub O). In both charts the horizontal axis is the subject distance and the vertical axis is Circle of Confusion, CoC. CoC here is the size of the actual de-focused point rather than the maximum acceptable CoC that is used as the sharpness criteria in depth of field calculations. However, in both charts there is a horizontal blue line representing the CoC typically taken as the sharpness criteria (negative diagonal / 1780 or 0.176mm per Professor Bigler.)

The first chart was calculated to be typical of the examples you have posted with the assumption that the photo was taken with an 8x10 negative and a 300mm lens at f/8 and focus on the human subject at 12 feet. The second chart reflects the same camera, lens and f-stop, but now focused at the hyperfocal distance, 210 feet.

What is immediately evident and interesting is that the CoC is not symmetric about the point of focus, but goes to infinity on the near side while asymptotically approaching a maximum (the asymptote) on the far side. In the hyperfocal case that asymptote is the CoC sharpness criteria.

Not quite so evident is that if you shift your focus to the near side of the subject, you will gain that bit of depth of field to the near side, and lose it on the far side, but also you will raise the asymptote or maximum CoC approached at infinity.

The first chart also illustrates what I said earlier, that when there is very narrow depth of field, that small part of the subject range where the CoC is less than the chosen sharpness criteria, (that is, within the limits of DoF), begins to be nearly symmetrical about the focus point, and so in that case the DoF is divided nearly equally ahead of, and behind the subject.

I hope this helps.

[mandonbossi]

Thanks so much to everyone who has contributed to this one, it is really appreciated! I must admit some of the more technical information given was a little over my head, so will have to learn it through trial I think.. I will try and absorb all of the information and see if I can crack the code!

Thanks again..

Best Regards

Mandon

[K. Praslowicz]

I would not be surprised one bit if he puts most of his effort on composing the scene and working with the sitters, then just focuses on the eyes and shoots at a moderate f-stop, and the 8x10 format does the rest.

Finally got around to shooting like this on 8x10, just to see. ~15 foot subject distance with a 360mm Fujinon. First one is f/8, second is f/22. I just focused on the eyes and let it rip. 22 seems to much, 8 looks delicious.