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Wednesday, 21 August 2013

Comments

I've been doing aperture bracketing and wonder when the mfg's will add it. On paper M4/3rds starts diffracting at f8. In practice f16 or f22 and it depends on light (or lack there of), distance between objects and to subject(closer being more noticeable).

If the lens is 'bad', and the sharpness is low, would that not give you a larger DOF, because it is harder to see where the marginal sharpness ends and it might be so bad that you cannot clearly see what the point of focus was.
And I did try such lenses! Early cheap zooms from 10 years ago, you could not tell where the focus was!

This might be another can-o-worms, but when does printer resolution come into play? My post-it calculation says that at 300 dpi, I have a resolution of about 12 dots per mm. Is that enough to resolve 4lp/mm? It seems awful close.

Depth of field, what an endless theme for debate... especially when it brings about a subject everybody loves nowadays: 'Bokeh'.
Ctein's article matches my own empyrical findings. My experience with 35mm film (which is considerably vaster than with 'full frame' digital) tells me shallow depth of field is something we have to deal with when shooting. It could come as a surprise to some, but with this kind of equipment it is actually harder to keep sharpness in every plane than to get the so-called 'bokeh'. With film it is usual for me to use very narrow apertures - say f/8 and f/11 - in order to increase depth of field. And even then it's hard to avoid that some portions of the image appear out of focus.
There's no science in taking pictures with lots of 'bokeh'. Making photographs with acceptable back-to-front sharpness is the real challenge when using larger formats. 110, APS and now 'crop sensors' made it easier to get sharpness across the picture and harder to get 'bokeh'. No wonder newcomers used to smaller formats believe 'bokeh' is a difficult technique.
So, despite the fact that many photographers in the film days used narrow depth of field for creative purposes, what we've got now with this 'bokeh' psychosis is a technical shortcoming being promoted to artistic status. Oh well.

Ctein, that may have been the best article i've read of yours. Detailed, yet concise, with your normal sprinkling of humor. Well done. (BTW, thanks for turning me onto the wider world of tea, it has been a pleasure trying some of the teas you mentioned in articles past.)

Dear Ctein, much as I respect your intellect and accumulated wisdom, I really don't think it's entirely reasonable to reduce everything to mere logic, experience and common sense. I mean where would the world BE if that was the answer to everything?

Say what you really think for heck's sake! This IS the internet you know. You can't argue with a flawless premise, where's the fun in that?

Paul Krugman has confronted this phenomenom of the repeating subject and has identified it as the Zombie problem ie no matter jow many times you step on it it still come back to haunt you. Lol. And no I didn't read the comments.

Dear Keith,

I wrote a column on how to determine your printer's sharpness back in 2010: http://theonlinephotographer.typepad.com/the_online_photographer/2010/01/how-sharp-is-your-printer-how-sharp-are-your-eyes.html .

Getting a quantitative measurement in terms of line pairs per millimeter is extremely tricky. You can't just print a bar chart and get anything meaningful, because the dither algorithms frequently respond oddly to repeating patterns. I've tested the large handful of good printers over the years, nowhere near a majority of the ones on the market. But the worst results I got were 8 lp/mm and the best 15. So it's a pretty safe bet that printer resolution isn't likely to come into play when you're worrying about depth of field.


pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
======================================
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 
=====================================

There are no Great Photographs with a shallow enough depth of field to draw attention - think about it! Show me a clasic photograph where a shallow depth of field has enhanced it.

Dear Jarrett,

Who cares? Really!

pax / Ctein

Mostly, that's not true—it's a little bit true, because the digital sensors are modestly smaller than the film formats were, but this is not majorly visible.

Eh, Ctein this needs explaining optically the DOF would increase with a smaller sensor (since the smaller the sensor the bigger the DOF right), but this would be counteracted by the smaller sensor pixel versus film grain. So if you pixelpeep (which is photographycally/artistically nonsense but fun to do) you see less DOF but in print you'd see more. So it's all about pixelpitch/Mpixels versus final print size? And both live in different universes.

In that case a pixelpeeper would see less DOF in a D800 then in a D600 right, while a photographer would be amazed at the large format prints he can get from the former? Now I mentioned that bacause that was exactly what was happening when I went from GF1 (12 Mpixel) to an OM-D (16 Mpixels), the prints (at the same size limited by the R2400) looked significantly sharper and crisper (at that size comparable to a GSW690 even to the point of not bothering with it anymore) while the image pixelpeeped looked less sharp especially in the DOF. So I looked at both images at 50% resolution and the difference fell to the positive for the OM-D.

So this article is a explaination for that feeling or hunch or bewildering experience?

Thanks Ctein.

Greets, Ed.

So for the kind of photography that the Olympus 17mm on 4/3 is likely to be used for - where shooting with an open aperture is not a priority - is the f1.8 actually sharper than the f2.8?

Ctein, it's common knowledge that Zombie lies and 'factoids' are not killed by stakes through the heart. No, they must be dispatched by shooting them in the head. It's probably most effective to use bullets made from silver recovered from Kodachrome processing, which is now in very short supply.

That may be the best explanation of a very complex subject that I have ever read. That's very hard to do. Richard Feynman would have been proud.

For an article aimed at the "practical" aspects of DOF, I'd have appreciated some more discussion of things like the application to different types of subjects, the role that subject distance / focal length combinations play etc etc. Maybe even some examples! When you start talking about microns and lpm I'm afraid my mind starts thinking "theory"

Agree 150 % with Mark Johnson. You were talking about your "perfect post" not so long ago. I loved the one you wrote on Jim Marshal (which lets me find his book with his contact sheets). But for technical discussions this one is just cristal clear. Well done !

Dear Ed,

I don't know the pixel pitches in the various cameras you've mentioned, so I'm not 100% certain, but it does sound like the bewildering experience you're describing exactly what I'm talking about: You are pixel-peeping photographs made from different cameras that have different physical pixels sizes, so the “circle of confusion” that you're looking at changes from camera to camera, instead of just looking at the results in a print.

~~~~~

Dear David,

I don't understand what this has to do with depth of field. Aren't you really asking about what aperture your lens is sharpest at? Well, that depends on the lens. It's not unheard of for lenses to be sharpest wide open, but it's far more common that stopping down 1-2 stops improves their definition.

I don't own the lens you're talking about. Easy enough for you to find out: put the camera and lens on a tripod, focus really, really carefully, and make a series of aperture-bracketed exposures. Then pixel-peep to your heart's content. You'll have your answer!


pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
======================================
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 
======================================

Dear Richard,

It's so irritating when you ask me questions that make me think [grin]!

I believe Mike had covered a lot of the practical aspects you're interested in in previous articles of his, and with everything archived here I didn't really want to cover previously-mined territory.

But your comments about microns and theory got me to thinking (always a dangerous thing). What you're talking about is the qualitative vs. quantitative. That's kind of orthogonal to theory vs. practice. Sometimes qualitative explanations work better; sometimes quantitative examples do. And different ones work better for different people. I felt like this article needed some numbers to tie it down to reality, because unspecific statements about different size blur circles and circles of confusion wouldn't register as well.

Clearly that worked for many readers, but not for you. One of those courses/horses things (or is it the other way around), I imagine. if you look back at the “sequel” article I linked to at the beginning of my column, you'll see that I presented no less than five different framings of the argument, to really nail a stake through its heart. Different ones resonated for different people.

But back to that orthogonality. Most of the columns on theoretical science I've written here haven't had quantitative examples. Even though they're about theory. There are couple of reasons for that. One is that I feel that when I'm trying to explain a conceptually-difficult subject, throwing numbers at laypeople usually doesn't make it any easier. Except when it does. When I was writing about the breakdown of local reality, I tossed a couple of made-up numbers into my cereal box analogy just to make it feel more concrete.

The other reason my theoretical science columns don't include a lot of quantitative stuff is that I can't do most of the maths! A curiosity of modern physics is that most physicists run into a math wall at some point. Mine occurs at a point before I am proficient in either quantum mechanics or general relativity. But I can read the stuff, and I can explain it to other people… Just so long as I don't have to create numerical examples to go with my explanations.

If some readers are having trouble imagining how this works, think of it this way: it's a lot easier to read enough of a foreign language to be able to get the gist of some text than it is to be able to speak it. I can read a moderate amount of French and Spanish. Don't ask me to converse!


pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
======================================
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 
======================================

Jarrett, you're kidding, right? Excepting the f/64 School, most photographers working with large cameras (Sally Mann, Jock Sturges, Joel Meyerowitz, Alec Soth, etc.) can hardly avoid using shallow DOF from time to time, and they often use it to great effect artistically. And that's not to mention the legion of acclaimed photographers who have employed selective focus in medium and small format.

--begin inspirational rant, here.--

Dear Latent,

Oh, don't even encourage this sort of intellectually bankrupt trolling by arging with it. Folks who start going on about how "Great Photographs" are or aren't made with X, Y or Z are either just trying to score status points in a meaningless debate or have no clue why people make photographs.

Really, none.

'Cause, show of hands, now -- how many folks reading this are into photography primarily because they want to make a "Great Photograph" (or, worse yet, some random Netizen's notion of what constitutes a Great Photograph)? Show of hands? Chorus of voices? Anyone?

{insert sound of crickets, here}

Yeah, exactly. Except for an insignificant number of poseurs, we all make the photographs that make **US** happy, using whatever techniques, aesthetics, and tools please us the most. Nothing, not one whit, more than that.

Ever so occasionally, one of us will land on a Great Photograph. Yay for us, when it happens.

But nobody, and I mean nobody, goes out to photograph each morning saying to themselves, "Today I must make a Great Photograph or my time will have been wasted, and so I must hew to the rules* of Great-Photograph-Making."

(*[imaginary])

--end inspirational rant, here.--

pax / Ctein

Are you claiming that 15-20 lp/mm is the limit achievable by medium format film? It sounded like that in the text of the article.

Dear Ed,

Not in the least. That's a complete misread. I'm not discussing inherent film or lens resolutions at all.

pax / Ctein

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