Diffraction Limited Aperture

[images_in_light_north_west]

The Digital pictute has published a Difraction limited table on there web site with the new 50D review, it looks to me

like canon are killing off Landscaoe photographers. This basicly tells me why I had problems with my 50D (returned)

its DLA is f7.6. I find myself shooting f11 alot of the time with my 5D, the 1DsMkIII is f10.3 as will be the 5D Mk II,

the 5D Mk I is f13.2. I think this tells a lot. I know when shooting there are many variables including atmosphere and

lens quality, tripod, blah, blah, blah, but I think Canon needs to recognize these limitations with current technology.

 

 

Link

http://www.the-digital-picture.com/Reviews/Canon-EOS-50D-Digital-SLR-Camera-Review.aspx

 

Table from the Digital Picture: (copy paste did not work well see link)

 

Model FOVCF Sensor Pixel Size Pixels/Megapixels Viewfinder DLA

Canon EOS Digital Rebel XS / 1000D 1.6x 22.2 x 14.8mm 5.7µm 3888 x 2592 10.1 .81x 95% f/9.3

Canon EOS Digital Rebel XSi / 450D 1.6x 22.2 x 14.8mm 5.2µm 4272 x 2848 12.2 .87x 95% f/8.4

Canon EOS Digital Rebel XTi / 400D 1.6x 22.2 x 14.8mm 5.7µm 3888 x 2592 10.1 .80x 95% f/9.3

Canon EOS Digital Rebel XT / 350D 1.6x 22.2 x 14.8mm 6.4µm 3456 x 2304 8.0 .80x 95% f/10.4

Canon EOS 300D Digital Rebel 1.6x 22.7 x 15.1mm 7.4µm 3088 x 2056 6.3 .80x 95% f/11.8

Canon EOS 50D 1.6x 22.3 x 14.9mm 4.7µm 4752 x 3168 15.1 .95x 95% f/7.6

Canon EOS 40D 1.6x 22.2 x 14.8mm 5.7µm 3888 x 2592 10.1 .95x 95% f/9.3

Canon EOS 30D 1.6x 22.5 x 15.0mm 6.4µm 3504 x 2336 8.2 .90x 95% f/10.3

Canon EOS 20D 1.6x 22.5 x 15.0mm 6.4µm 3504 x 2336 8.2 .90x 95% f/10.3

Canon EOS 10D 1.6x 22.7 x 15.1mm 7.4µm 3088 x 2056 6.3 .88x 95% f/11.8

Canon EOS 5D 1.0x 35.8 x 23.9mm 8.2µm 4368 x 2912 12.8 .71x 96% f/13.2

Canon EOS 1D Mark III 1.3x 28.1 x 18.7mm 7.2µm 3888 x 2592 10.1 .76x 100% f/11.4

Canon EOS 1D Mark II N 1.3x 28.7 x 19.1mm 8.2µm 3520 x 2336 8.2 .72x 100% f/12.7

Canon EOS 1D Mark II 1.3x 28.7 x 19.1mm 8.2µm 3520 x 2336 8.2 .72x 100% f/12.7

Canon EOS 1DS Mark III 1.0x 36.0 x 24.0mm 6.4µm 5632 x 3750 21.1 .76x 100% f/10.3

Canon EOS 1DS Mark II 1.0x 36.0 x 24.0mm 7.2µm 4992 x 3328 16.6 .70x 100% f/11.6

[bobatkins]

It's not quite as bad as the mathematical analysis might suggest (or rather the strict DLA model isn't really applicable to the real world situation.

 

See http://www.bobatkins.com/photography/technical/diffraction.html for a more practical analysis, along with sample images.

 

It's certainly the case that the effects of diffraction at a particular aperture become less as format size goes up, but that should not be a surprise to anyone. Larger fprmats give sharper prints and allow the use of smaller apertures. If they didn't, the 8x10 (and 11x14) camera would never have been invented!

 

However, worrying about aperture limitations when using APS-C DSLRs is probably somewhere around issue #89 on the list of the top 100 things that are wrong with your pictures. For 95% of users in 95% of situations, it's a non-issue. It should only cause sleepless nights for the most technically obsessed of photographers. It's always been the case that you'll get the shapest possible images with most lenses set to apertures between around f5.6 and f8, because that's the "sweet spot" between reducing Seidel aberations (mostly Spherical abberation) and increasing diffraction. That basic rule holds just as well for APS-C as it does for full frame since they aren't really all that different in size. WIth really small sensors (digicam), diffraction kicks in earlier, so they may peak at f4 or so.

[philip_wilson]

Interesting article - I am glad i ordered the 5D mark II although I wonder about being an early purchaser - almost all recent Canon DSLR have had issues (1DMkIII focussing, 1DsMkIII mirror alignment, 50D errors) so I await the 5D mark II with trepidation. I wonder if anyone has looked at the quality factors from a combination of lens resolution (there are a few posts that suggest that the pixel density of the 50D exceeds most lens resolution) and the issue of diffraction limits. The solution to lens resolution is to use wider apertures (F8 is typically the best lens performance) while diffraction requires smaller apertures. Bob may well be right that in the real world at F5.6 or F8 these issues are not material. I do find it interesting how Megapixels, video, image stabilization and live view have become the basis of competition for DSLRs. Many things that I like (e.g. viewfinder, handling, solid build and fast responses) appear to have lost attention as customers look for other things. The old Canon AE1 was a mass matket camera but when I compare it to the Digital Rebel it looks like quality engineering. I also love the shutter response of my old Canon 1NRS with the pellicle mirror - even though the 1V has the same frame rate and better AF I still like the response an continuous view from the 1NRS. In some ways it is a shame Canon abandoned this technology (especially as it may well provide top AF performance in live view). Even in terms of AF as far as I can discern the 1DMarkIII does not appear to perform any better than the EOS1V (I have not seen any comparisson tests).

[anders_carlsson]

It's apparently not only about format. The article also says: "As pixel density increases, lens aberrations are magnified and more readily apparent at a 100% viewing size." Interestingly, the difference between the 20/30D and the 50D is about the same as between 5D and 20/30D. Comment, anyone?

[zml]

<i>at a 100% viewing size." </i><br>Yep, that just about sums it up...

[bobatkins]

"As pixel density increases, lens aberrations are magnified and more readily apparent at a 100% viewing size."

 

Translation - the closer you look at an image, the more resolution you have, the more deviation from "perfect" you see. Applies to most things (even people...).

 

"lens aberrations are magnified" is a bit misleading. The image is magnified too. It doesn't mean that aberrations actually get worse with more pixels.

[gregf]

Look, Until 2 months ago I shot 24x36mm slides exclusively. I personally thatnk that you are nit-picking to find minor aborations at full resolution.

 

Under the lupe, every slide looks great...when I look at the RAW file from my 5D at 100% I see some issues, but unless I am planning on enlarging to maximum size, these are just meaningless.

 

No lens will be perfect, especially at 21MP. Remember, most people won't look at an enlargement and see a small area that's not perfect.

 

yes, it's nice on digital to look at every corner of the photo...but realistically, nothing is perfect. I personally, think we have come to the point where we over analise every photo.

[g dan mitchell]

<p>People frequently misunderstand what so-called "diffraction limits" are telling them. For example, I know that some infer that a

sensor of a

given size with a higher photosite density will not produce good images at apertures as large as they might use on a camera with less

photosite density. Translated: "A 50D won't do as well with detailed images as a 40D" or "If I get a 50D I'll have to limit myself to

apertures no

larger f/5.6." (Or pick some other aperture.)

 

<p>The assumption seems to be that increasing photosite density might be a Bad Thing because the "diffraction limit" will occur at

larger apertures and that certain apertures will now be beyond the "diffraction limit."

 

<p>When it comes to the effect on actual photographs, this is nonsense.

 

<p>Here is what actually happens. Pick a reference camera - let's use a 8MP 20D. Put a lens on the camera and set it to some typical

aperture -

let's say f/8 - and make a photo. Now put the same lens on a 15MP 50D, set it to the same aperture, and make an identical photo of the

same subject.

 

<p>Now use good workflow/post-processing to make two best-case prints, one from each of the two test cameras.

 

<p>There will be <b>exactly the same amount of diffraction blur</b> in the two prints. (Techically, the higher photosite density camera

might

produce a more accurate image of the diffraction blur, but it won't produce any <i>more</i> diffraction blur. And, technicalities aside, you

won't see any difference.) The "amount" of diffraction blur is not a function of photosite density. When it comes to diffraction blur's effect

in a print it is a

function primarily of aperture and sensor/film format. Photosite density has nothing to do with it.

 

<p>On the other hand, there <i>could</i> still be a small benefit from the higher photosite density sensor since it might be able to

produce a

slightly better image with high quality lenses with photographs that are made at slightly larger apertures.

 

<p>There may be reasons to prefer a lower photosite density in your camera, but worry about being "diffraction limited" is definitely

not one of them.

 

<p>Dan

[ed_okie]

Bob Atkins' descriptive shoots way too low, "For 95% of users in 95% of situations, it's a non-issue. It should only cause sleepless nights for the most technically obsessed of photographers."

 

99.9% comes closer to the target's bullseye.

 

"...sleepless nights for most technically obsessed of photographers." Bob, where do you come up with such great lines? Couldn't have said it better. Pixel-peepers another descriptive. The purpose of taking pictures is surprise, surprise - the photograph, the results! How it was done is irrelevant.

[sarah_fox]

Ed, the purpose of golf is, surprise, surprise, to put the ball into the hole. "How it was done is irrelevant." OK, you can make that case, but I think it will fall flat on the better golfers. Attention to the multitudes of details that amateurs find ridiculous is part of what enables pros to deliver consistently superior results. Knowing one's optics is part of that equation for a photographer.

[g dan mitchell]

"Ed, the purpose of golf is, surprise, surprise, to put the ball into the hole. "How it was done is irrelevant." OK, you can make that case,

but I think it will fall flat on the better golfers. Attention to the multitudes of details that amateurs find ridiculous is part of what enables

pros to deliver consistently superior results. Knowing one's optics is part of that equation for a photographer."

 

But _misunderstanding_ a basic principle like this one is an example of the sort of thing that _distracts_ photographers from those

important details that actually make a difference in their photography.

 

The diffraction blur difference between a 12MP and 21MP sensor is not merely unimportant, it is non-existent.

 

Dan

[bobatkins]

"...Attention to the multitudes of details that amateurs find ridiculous is part of what enables pros to deliver

consistently superior results. Knowing one's optics is part of that equation for a photographer...."

 

Not really. There are well known photographers who don't know one end of a camera from the other in a technical

sense. They have talent and vising. They don't need to know the minutiae of optics or digital processing or the

number of line pair per mm a sensor or lens will resolve. They're photographers not physicists.

 

Then there are those who know everything there is to know about digital processing, sensor design and optical

aberrations, but who couldn't take a decent photograph to save their lives, despite owning the latest techno-wonder

cameras and lenses.

 

I'm not sure that knowing the details doesn't actually hurt some people since they spend more time worrying about

bit-depth, signal to noise ratio and dynamic range than what to shoot and when and how to shoot it. Perhaps the

best photographers are those who know all the details - then forget them.

[eric merrill]

Right now, my "longest" setup for birds/nature is a 300/4 + extender + 1.6x crop sensor. I usually use

the 1.4x. That gives me an "effective" 672mm setup.

 

<p>

Sometimes that isn't long enough. I was really surprised that I could get a decent 8x10 out of this by

cropping even further. If I had been using a single lens on a film camera, I would be using the equivalent

of an 1800mm lens.

 

<p>

<img src="http://www.merrillphotography.com/canid/pics/080216_008b.jpg">

 

<p>

Now, I'm not going to put a National Geographic photographer out of work with shots like this. It's more

of a record shot ("I was here. I saw this. I'm recording the moment.") than a work of art.

 

<p>

I thought it was pretty cool I could actually make an 8x10 that didn't look like crap given all of the above.

I have found that the more extreme the enlargements I make, the more critical it is that I pay attention to

the sweet spot for the given setup I'm using. This is stopped down two stops, for an effective aperture of

f/11. Through my own testing, I found that's the best aperture for the above setup to yield maximum

quality. Opening up or closing down from there shows less resolved detail at extreme magnifications.

 

<p>

I understand it could be argued that if I were a better naturalist, I would have found a way to get closer

so I was using the entire sensor area I had available to me. No doubt that would have also made for a

technically better picture, too. But I wasn't closer.

 

<p>

There is value in pixel peeping in rare instances. This is an extreme example for me. I don't usually

crop and enlarge to this extreme. But when I do, it's nice to know what I need to do in order to coax out

as much quality as I can.

 

<p>

Eric

[sarah_fox]

Dan and Bob, would you dare hint that Ansel Adams was a bad photographer because of his obsession with technical details? Granted, good photography is much more than attention to details, and some photographers can somehow make great photographs with hardly a clue about what they are doing. However, I believe that the best photography takes both a creative mind, an artistic eye, thorough technical knowledge, and careful implementation. My post was not in response specifically to the diffraction issue, but rather in response to the tech-bashing that is so casually and indiscriminately thrown about, including the pejjoritive use of the term "pixel peeper." It really gets a bit old.

 

I can understand your wanting to encourage people to do less navel gazing and more shutter clicking. However, when people are trying to research the equipment they need and are trying to refine their technique (the reason many come here), they legitimately need to do a bit of navel gazing. What is wrong with that, and why should it be criticized?

[g dan mitchell]

<p>Sarah asked a very important question: <i>"Dan and Bob, would you dare hint that Ansel Adams was a bad

photographer because of his obsession with technical details?"</i>

 

<p>No. Absolutely not!

 

<p>As someone who perhaps knows more about Adams than the average photographer

you are probably aware that he not only was a meticulous technician* with camera and in the darkroom, but also that he was interested

in

new

technologies including color and Polaroid media. In the end, though, I would point out that his obsession seemed to be

directed straight towards the creation of powerful and expressive photographs, and I would add that his technical prowess was based on

deep personal knowledge, extensive practice (e.g. - real world testing). In the Adams writings that I have read, "sharpness" doesn't

seem to be an issue he spent a whole lot of time on, especially in comparison to a host of other issues.

 

<p>The point of my post about diffraction was not that being concerned with

technical details is a bad thing. (I actually pay a lot of attention to this stuff in my own photography.) If you think about it, my point was

more the <i>exact opposite</i> of that. In this

case, what we have is not just an "obsession" with an issue that is less important to the quality of photographs than the

OP might think, but we have an obsession <i>based on a misunderstanding of an important technical issue in

photography.</i>

 

<p>To put it more crudely: <i>If one really understands this technical issue** the question turns out to be irrelevant.</i>

 

<p>I'm pretty certain that's what Bob was thinking, too - though I can't speak for him. And from what I know about him, I think Ansel

would

agree, too.

 

<p>Take care,

 

<p>Dan

 

<p>*Though, as you probably know, some of his best known photographs did not result entirely from carefully planned and executed

shooting.

 

<p>** The technical issue actually being two issues: how diffraction works and how digital sampling works.

[bobatkins]

Ansel Adams wasn't technically obsessed with equipment. Read your photography history. He was obsessed with the quality of his prints and making them reflect what he saw (and felt) at the time of shooting. There's a difference. Equipment was a means to an end, and a relatively minor component in that process.

 

I think Edward Weston (who was at least as obsessed with photography as Adams) did a lot of his work with an old lens he picked up at a flea market in Mexico. I doubt he ever though much about lp/mm or whether his view camera used carbon fiber rails.

 

"...for 25 pesos I purchased a Rapid-Rectilinear lens in a cheaply made shutter. Now I start a new phase of my photographic career with practically the same objective that I began with some twenty years ago. My expensive anastigmatic and my several diffused lenses [standard tools for the Pictorialist photographer] seem destined to contemptuous neglect, though it may be that I shall dust them off for an occasional portrait head...."

 

Doesn't sound like a man who would be pixel peeping much.

[sarah_fox]

Dan, I do get your meaning -- and agree with you. ;-)

 

Bob, I wasn't referring to equipment obsession, but rather to method obsession, for which Adams was a poster child. My point was that one CAN be obsessed with the little details and still somehow manage to produce meritorious work. I think most would argue that conscientious attention to detail makes a good photograph even better -- a belief I'm certain you must share. I'm personally trying to improve on what I recognize are a few of my technical shortcomings.

 

This "pixel-peeper" finger wagging is nothing new to me. I was roundly criticized decades ago for my attention to film grain structure. People laughed at my use of weird and antiquated films such as Panatomic-X and unusual developers such as Microdol-X. I was criticized as much then for my use of primes then as for my use of zooms now. I was criticized as much then for not using Canon gear as I am now for using Canon gear. I was criticized as much then for tripod use as I am now for handholding. And now I'm apparently one of those dreaded "pixel peepers" -- a term that screams for a law to prohibit the perverse practice. All this while I've actually been able to do photographic work, despite my attention to details that some people insist I should ignore. I'm still learning, and I'm still trying to improve, and if I'm lucky, I'll never run out of new ways to grow as a photographer.

 

I hope my point in all of this is not lost. It is merely an appeal to you and to others to have a bit of tolerance for those who do photographic work a bit differently or pay attention to different issues. Photographers are a pretty diverse lot, no? There is a place in photography for meticulous technicians (which I am not, appearances to the contrary), and there is also a place for a local artist who I swear must take photographs without a lens.

 

Mostly, when I dare to peep pixels after a shot, I really wish everyone would refrain from laughter. Only last Saturday I grabbed a shallow DoF shot that I *thought* was entirely in focus, but one of the figures was rather soft. I *wish* I had peeped that photo a bit better, because I would have had the opportunity to re-shoot, but I didn't. I blew it. As a result, I had to aggressively USM the soft part of the image and touch up some of the objectionable edges, with less than stellar results. It was such a wonderful shot that I could have done better because I wasn't an adequate technician -- still a keeper, but not as good a keeper.

 

So with everyone's permission and good blessings, I think I'll continue to peep pixels. I'll just have to pack earplugs in my camera bag to silence the uproarious laughter.

[g dan mitchell]

<p><i>"My point was that one CAN be obsessed with the little details and still somehow manage to produce meritorious

work."</i></p>

 

<p><b>That</b> is a point I can agree with. In fact I've posted a few times (mostly elsewhere, I think) when folks have

assumed that a) those who are interested in the affective qualities of photographs don't know their technical stuff, or b)

those who are interested in technical stuff aren't capable of (or interested in) "actually making photographs."

 

<p>I come from a background in music, instrumental music to be precise. Perhaps because of this I've always known

that for almost everyone who produces or aspires to produce this thing called "art," integrating the "technical" and the

"affective" ("objective" and "subjective?") parts of the process is critical. You can't make beautiful music on an

instrument unless you first master the technique of that instrument; the mastery of technique is useless or a parlor trick

unless you apply it to producing beautiful (however you define that) music.

 

I believe strongly that it is the same in photography. You have to understand the technical aspects of whatever

equipment (or instruments?) you use, whether this includes a view camera, a DSLR, or a Holga. But understanding that

technical stuff only is useful to the extent that it lets you create photographs.

 

Dan

 

(Who can already imagine a few exceptions to the above, with is why he used words like "almost" and "believe." :-)

[sarah_fox]

Dan, I'm glad you resonate with my point, as I agree with your points too. I consider your work (which I admire) a perfect example of my point.

 

As I said, I'm trying to grow as a photographer. I am a fledgling pro, relatively speaking, and I can no longer rely on luck of the shot. When I'm on the job, I'm expected to deliver quality work 100% of the time, and I don't feel I'm close enough to that 100% bar. There is no experience so humbling as a re-shoot, except perhaps for a critical wedding shot botched. My personal goal is to master a more disciplined routine/workflow that yields more consistent implementation with fewer errors. I hope others understand some of my prior remarks in that context.

 

That said, this sort of shooting has nothing to do with my artwork, which is more of an "in the moment" sort of thing, often experimental, with much more margin for error. ;-)

[bobatkins]

There's absolutely no need to know anything about sensor resolution or esoteric optics to take good wedding photos. You need to know how to organize, pose and light.

 

From what I've seen an read in a multitude of forums, the more technical information the average photographer has, the more confused they get and the more time they spend worrying about things that will have little or no influence on their work. I wouldn't be at all surprised to find that 50% of the things that people "know" about the technical aspects of photography are, in fact, wrong. I see stuff posted all the time that is simply wrong. People think they know the subject, but have picked up random bits of information and badly misinterpreted their meaning and/or significance, or have simply not understood them.

 

If someone wanted to be a better professional photographer, I'd suggest they take courses in business, composition and perhaps lighting, not a Ph.D in optics, electronics or computer science!

 

I think there are probably more wonderful photographers with no technical knowledge than there are well educated technical specialists who are wonderful photographers.

 

I'm not arguing for ignorance, just the best allocation of limited resources. Spend time on what will do the most good.

[zml]

There is photography, there are photographers and then there are photographs. The knowledge of photography (a technical activity, even if only a shoe-box pinhole camera is used to create heliograms on a piece of blue fabric) is necessary to a photographer to make a photograph. Assuming that one’s purpose is indeed producing a photograph, not the equipment in itself, the extent if this knowledge may vary: from gearheads obsessed with equipment, on a perpetual quest for a “better” thing, to people who are content with some familiarity with “how the stuff works”, to people who don’t give a flying hoot about the gear as long as it works for them. Any of these photographers can produce exceptional photographs, stellar both in terms of content and technique, because it is not the equipment – it is how you use it. I for one am amused by the “did Shakespeare care about the anatomy of the goose that grew the quill he was using” discussions: even if he did, it was irrelevant to his endeavor - he simply knew how to write with it…

[sarah_fox]

Bob, I do understand and appreciate the point you are trying to make, and I don't entirely disagree with it. However, I

also consider it a "glass-half-empty" sort of perspective that doesn't give people enough benefit of the doubt. You an

I both have empirical backgrounds, so I'm sure you can appreciate that my own personal experience, empirically, is

that my photography has improved as my technical knowledge and skills have improved. It has also improved as I've

acquired equipment better suited to my needs. That's not to say these things have had a whit of impact on

my "creativity" or "vision" as a photographer. Creativity and vision usually don't come without maturity and an

advanced degree from the School of Hard Knocks. However, my ability to implement my ideas has improved greatly,

as has my ability to implement the needs of others (i.e. commercial work). An idea without implementation can't be

hung in any exhibit!

 

I still maintain that good photography is both creative AND technical. Both are necessary; neither is sufficient by

itself. I do include in the "technical" the ability to make appropriate equipment selections and to operate the

equipment competently. Perhaps there is a point of diminishing return over which we are quibbling. Irrespective, I'll

continue to sweat the little details, and I'll continue to extend my knowledge and skills. I do think that improves my

work, regardless of whether the same general approach improves anyone else's.

 

And not to lose the point *I'm* trying to make, I only wish folks would stop ragging on other folks for doing

photography a bit differently. Different strokes for different folks! With this thought, I'll suggest a third element of

good photography, which is enthusiasm. All this neck biting about pixel-peeping-this and film-vs-digital-that reliably

damps or kills enthusiasm, and that cannot be good for photography. I've done it myself (and regretted it), but I've

vowed not to do it anymore and to call others on it when I see it happening.

 

Now... back to editing some really cool images I shot last weekend. ;-)