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A simple tip for improving focus sharpness

Jerry_R

New member
Sharpness is a bourgeois concept. - Henri Cartier-Bresson
Maybe he meant slightly different? I have many photos, that are not in focus, and are great, I like their climate a lot. These are rather situations, when nothing is sharp, we see only contour of people, someting like this.

But I hate when I try to focus eg. on eye, but got back or front focus. When I used Summarits - I had no problem.

Since I use Lux'es - I put magnifier 1.4x, but only when used at 1.4 and from close distance (70-100cm).
If distance is further or aperture is closed slightly - I have hit rate so high, that I can only blame myself.

PS: me gear was once at Solms for calibration

PPS: I try to remember unconsciously position of focusing tab as starting point.
I mean I can set it to close position - before raising camera to the eye.
 

dannh

Member
Sharpness is a bourgeois concept. - Henri Cartier-Bresson
I'm curious of the context around this quote. Was he targeting "film peepers" of his day? After recently visiting the Cartier-Bresson exhibit at the SF MOMA, I don't remember a lot of OOF shots, but then again, he was shooting film.
 

TRSmith

Subscriber Member
Not to muddy the waters, but I could use some clarification on the business of depth of field with regards to the long-standing notion that it extends 1/3 in front of the focal point and 2/3 beyond it. I recently read an explanation on the site that sells those fancy focus checking devices and the guy who sells them claims that the 1/3-2/3 thing is a myth. That in fact, depth of field is actually spread almost equally before and behind the focal point.

I have always operated on the assumption that the 1/3-2/3 rule was true. Is it fact or myth?

Thanks!
Tim
 

Godfrey

Well-known member
I'm curious of the context around this quote. Was he targeting "film peepers" of his day? After recently visiting the Cartier-Bresson exhibit at the SF MOMA, I don't remember a lot of OOF shots, but then again, he was shooting film.
Don't know whether this is true or not, but it's a starting point:

http://jimaustin.wordpress.com/2011/02/27/florida-series-impression-vs-reality/

This quote expands his thoughts on the subject nicely:

http://vizualpoetry.com/Henri-Cartier-Bresson-quotes.html

I’m always amused by the idea that certain people have about technique, which translate into an immoderate taste for the sharpness of the image. It is a passion for detail, for perfection, or do they hope to get closer to reality with this trompe I’oeil? They are, by the way, as far away from the real issues as other generations of photographers were when they obscured their subject in soft-focus effects.

-Henri Cartier-Bresson, on technique.
"American Photo", September/October 1997, page: 76
 

Godfrey

Well-known member
Not to muddy the waters, but I could use some clarification on the business of depth of field with regards to the long-standing notion that it extends 1/3 in front of the focal point and 2/3 beyond it. I recently read an explanation on the site that sells those fancy focus checking devices and the guy who sells them claims that the 1/3-2/3 thing is a myth. That in fact, depth of field is actually spread almost equally before and behind the focal point.

I have always operated on the assumption that the 1/3-2/3 rule was true. Is it fact or myth?
IMO, most of the people chasing autofocus accuracy with those laughable toys are as misguided as the HCB comment I just posted suggests.

In this case, it's *very* easy to take out your camera and do a little first hand ground truth. I think you'll find that the "one-third front, two-thirds back" rule of thumb is pretty darn accurate most of the time.* The mathematics supports it too. ;-)

* With the proviso that the set focus distance isn't beyond the hyperfocal for the given lens and aperture. Once you're focusing past the hyperfocal, you can indeed place the focused plane exactly such that DoF extends equally in front of and behind that plane, or you can move the focus plane around to get nearly any proportions of front/back in focus depth you want.
 

dannh

Member
I probably should have said this up front, but I'm not a pixel-peeper. I just think that my images look better when they are in focus. That's the only thing driving my curiosity about focus techniques.
 

Jerry_R

New member
Just go and shoot eg. this:
http://www.whibalhost.com/lensalign/
of course you can build quickly something similar by yourself using ruler.

And you will know the answer. Personally I found some lenses that follow 1/3 - 2/3, some that are closer to 50 - 50.

But for sure it is myth that ALL have the same split.
 

Godfrey

Well-known member
Just go and shoot eg. this:
http://www.whibalhost.com/lensalign/
of course you can build quickly something similar by yourself using ruler.

And you will know the answer. Personally I found some lenses that follow 1/3 - 2/3, some that are closer to 50 - 50.

But for sure it is myth that ALL have the same split.
The laws of optics and the mathematics of depth of field makes this notion impossible. I invite you to review the DoF equations posted on the DOFMaster site:

http://www.dofmaster.com/equations.html
 

TRSmith

Subscriber Member
So, for us simple folk, what you're saying is that the notion of 1/3 in front and 2/3 in back is NOT a myth and that when shooting, it's a safe "rule of thumb" with which to work. True?
 

jonoslack

Active member
So, for us simple folk, what you're saying is that the notion of 1/3 in front and 2/3 in back is NOT a myth and that when shooting, it's a safe "rule of thumb" with which to work. True?
Terry - us simple folks use practice - knowing (in principle) how to get it in focus is very interesting, but it's not nearly as useful as knowing (in practice) how to get it in focus .. . . . . . . . and in my very humble opinion practice is where it's at.

. . . and as a little irrelevant aside, I have more than one manual focus lens, and I've learned that whether to come from infinity or close up depends on the circumstances and the lens.

I think it's a bit like reading books about how to do sex - it certainly can be useful, but practice and experience is probably a better tutor.
 

Godfrey

Well-known member
I did, I open:
http://www.dofmaster.com/dofjs.html

I select M9, 35mm at f/1.4, distance 70 cm. And see split: 49% - 51%.

I change distance to 600 cm and receive 40% - 60%.

Is this wrong?
No, what you're seeing is the fact that at short focus distances, the curves are closer to 50-50. That's because the near and far 'acceptable focus' limits are not defined as a linear progression, they're a geometric progression. The same characteristic will be true of ALL lenses as you walk the DoF curves for near and far from close distance to far distance settings.

The 1/3-2/3 rule of thumb is a first order DoF approximation for use when shooting at normal subject distances, e.g.: 5 to 20 feet and beyond. As you focus closer than that, the lines representing near and far converge to an asymptote.
 

Godfrey

Well-known member
So, for us simple folk, what you're saying is that the notion of 1/3 in front and 2/3 in back is NOT a myth and that when shooting, it's a safe "rule of thumb" with which to work. True?
Yes, for normal subject distances.
For close up work, the rules change. :)
 

TRSmith

Subscriber Member
Makes sense. Thanks. Nice to have a long-held belief reinforced with a little math (as long as someone else is doing it).

Tim
 
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