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Wednesday, 28 April 2021

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Sigh! Some declining minority of us still cringe when you write that bokeh is defined as out-of-D-o-F-blur instead of the quality of out-of-D-o-F-blur.

… Don't throw bokehs at me
Don't please my focus too much..

Sigh, Bokeh. The newest fad. A few years ago, it was equivalence, and before that, megapixels or well depth. Actually taking meaningful photographs, nah, who cares about that when you can have mega-bokeh.

[Well, if by "newest" you mean nearly a quarter of a century old, with the actual properties around since the beginning. --Mike]

It also matters how far you view the picture from - part of the effective enlargement.

On your point on wrong focal plane, I have one that demonstrates this nicely. It's one of my favourite compositions (4 attentive lionesses in a a row in long grass). Unfortunately, I missed focus with plane of focus on the long grass about 3ft behind.

I placed it strategically at the end of a corridor so it's usually seen from afar, then the mis-focus is a lot less obvious!

This is always something that has bothered me. Are we "looking at photos as photos" or analyzing math?

I have a Nikon D700 with a modest 12mp. When Nikon came out with the D800 series and tripled the megapixel count, people (on various forums) were suddenly abandoning legacy glass that overnight were deemed as no longer viable optics. How can a lens that was used on Fujifilm Velvia and Kodachrome 25 no longer be good?

Me, I just keep using the D700. The photos look good... guess that makes me stupid for not buying into the megapixel hype.

Peter Karbe has recently given some presentations on the evolution and design of Leica M and SL lenses. In the discussion of SL lenses, he talks about the steep contrast falloff of the SL APO Summicrons, including his “best performing’” SL 35 APO Summicron, giving the impression of decreased sharpness, such that performance at f2 resembles f1.4. See from about the 28:30 mark in this video. He shows a graph plotting distance/DOF and contrast.
https://m.youtube.com/watch?v=_vyoAIOTIcs

Thanks for an enlightening article, Mike. What have you gained if the subject's eye is perfectly in focus but the rest of the face is out of focus? Let's hear it for f4!

Ironically, depth of field determination has become much harder without a single focal length manual focus lens and usable depth of field scales.

Fantastic post. I always had a good basic understanding of this, but your presentation is the best explanation I've read. Well done. So tomorrows lesson will cover that equivalence thing between a 20mp m43 sensor with 25mm lens at f8 vs 20mp FF and 50mm lens at f16...?

A great example of exactly what you are talking about are pinhole images on a platform such as Instagram when viewed on a phone. They appear almost as any other photo being presented (i.e sharp). Pinhole images, as you well know, are really not sharp.

It suddenly dawns on me (and I might be wrong, though I don’t think so) that all the times I have come across someone declaring, on some photography site or other, ‘I always shoot wide open’, it was a male photographer who made that statement...

Mike, why are you afraid of leaving such a comment? It is true, it can be checked. You can say, nice picture, but when looking at it at 100% I noticed that the focus was slightly off. You are too nice a guy. Anyway, I agree 100%, I upgraded to 50MP camera, and now I notice when the focus is slightly off. But if the picture is good enough, I don’t care! I lower the resolution, and presto! A slightly off 50MP, becomes a 15MP sharp enough picture!

In other words, higher resolution makes the circle of confusion smaller.

“Sharpness is a bourgeois concept” is a favorite quote by Henri Cartier-Bresson. Case in point, Dorothea Lange's Migrant Mother photo is focussed on her shoulder and her face and eyes are not in focus. Damn that high resolution camera she was using with that fast lens! Still, one of the greatest photographs of all time.

"So the higher your system resolution, the less will be in focus for any given aperture."

A different, perhaps memorably metaphorical, way to envision this phenomenon: The more you know, the less you like.

Every extra bit of information in any image expands the opportunity to lessen clarity. I'm observing this right now as I began working with the Fuji GFX 100s last week. It's an absolutely staggering piece of technology for the price. But even with its outstanding IBIS and class-leading AF system you really have to keep that camera rock still if you really want to achieve the maximum sharpness control.

But tech to the rescue! During the past year or so I have been using a utility that employs artificial intelligence to the job of bringing greater focus and sharpness to high-res images. Its latest incarnation is nothing short of magic. It can differentiate between motion blur, general lack of sharpness, or just plain blown focus. Running it on a 104Mp image (200+ Mb) can take some patience. But the good news: if you're using an Intel x86 processor you can grill a burger while waiting! (Apple's M1 doesn't even breathe hard.)

I run into this issue often when I try to make the odd extra-large print or try to use a small cropped area. Of course, some great classic photographs are soft. Like blur, sometimes too much sharpness or detail can detract from a picture's impact or intent.

Thanks for the resolution vs DOF explanation, especially that wonderful nostalgia-evoking ASCII diagram! It's quite clear (not a pun!) and makes a lot of sense.

Would this hold for the human eye as well? That is, is our DOF shallower in dim light because of larger aperture? I suppose that would be offset somewhat by the fact that in dim light the cone-rich high-resolution center of our retina isn't much use, so we'd also have lower resolution, therefore higher DOF. I wonder how the two phenomena balance out. Or would other factors like contrast matter more?

My first camera had no electronics or autofocus. At that time the saying was "f8 and 1/125s and you'll be OK most of the time". I still almost always shoot at f8 as the best compromise. Of course there are exceptions. Very small apertures cause their own blurring problem. For macro work I use stacking and merging software when I want everything in focus. Not rocket science and something I just do without having to belabor it.

I always want to say “good grief!” when I see heavily saturated, clarity slider maxed photos but I don’t. People like different things. Missed focus is just bad technique. I have been guilty of that. We are getting our two 100s soon. We are totally psyched.

Well said. Unfortunately this tends to get blamed on the tool in use at the time - auto focus no good or rangefinder out of calibration. Hey-ho.

Back when I was a young dawg I used a Nikon F, and then later FG with a 50mm f/1.8 Ai manual focus lens. I didn't even know what bokeh was. I primary aim was always to get the exposure correct. With the F I had a hand held light meter, and the FG had one built-in (center-weighted). Anyway, I always found myself shooting f/4-f/8 range to get the shutter speed I wanted with the film I was using (either ASA 200 or 400 typically).

The good 'ol days, lol. F8 and be there.

It seems self-evident to me that autofocus and the rise of smart-phone-as-camera have basically taken deliberate focus and strategic use of depth of field out of the equation for the overwhelming majority of photographs being taken these days.

Back in the day, one of the delights of a decent manual focus SLR was the relative ease with which you could snap things into focus through the viewfinder. You could *deliberately* bring the subject's face, or a particular flower in the garden, into the sharpest point of focus.

Nowadays cameras do that for you. Yes, you can choose where that point of focus will fall with enough effort and knowledge of how your camera works. But I'd hazard a guess that most folks just point at the subject and trust the camera to figure it out. Smart phones with their tiny sensors, giant depth of field, and built-in focusing algorithms make choosing focus almost irrelevant. Everything's kinda sorta in focus.

So I have some sympathy for folks using a fast lens and shooting wide open just because they can. At least it doesn't look like a billion other smart phone shots.
Except for the ones with the phone's "shallow DOF filter" applied.

Mike, You have described the ultimate DOF of the pinhole camera!
But you also need to clarify that DOF and Bokeh are different.
DOF is an approximation of apparent sharpness, dependent upon several factors including those you mention, in the spaces before and behind the plane of sharp focus.
Bokeh is the subjective appeal of the shape and character of objects in the out of focus areas of the photograph. There is this myth that all one needs is a large aperture lens having a circular aperture, but there is more to it than that.

The film era Schärfentiefetabelle from Leica shows the depth of field for 90 mm lenses at f/5.6 and a distance of 2 meters to be between 1.92 and 2.08 meters. For 80mm lenses it is 1.90 to 2.11 meters. These values are for a circle of confusion of 1/30 mm.

The OLED display of my 85 mm Batis shows a depth of field of + .04 and - .04 meters for the same f-stop and distance. That is using the R version of the Sony A7 camera. I wonder if the display will shown higher values for the non-R versions. Probably not, but it should.

Anyway, this underlines what you are saying in the second paragraph.

This web-based depth of field simulator is pretty awesome for those who want to experiment. You can even select your camera and lenses to try out certain settings and see the results on the simulator. https://dofsimulator.net/en/

Kind of the whole purpose of a photographer producing a final print of their image--the ability to control the actual size they want it to be viewed. And what THEY want the image to be seen as. Perhaps the most disturbing direction of photography, viewing most digital images.

Agree that the fashion for only using lenses wide open is only tenable if photographers are willing most of the time to have large swathes of their actual subject out of focus. I’ve even read a comment from someone who bought a classic lens with jammed aperture blades. It was fine, they said, because it was jammed *wide open* which was the only way they shot....

But I also have learned not to judge other’s photos by close inspection. That lesson came from attending an exhibition of large prints by Yousuf Karsh. Standing nose to nose with Ernest Hemingway (one of Karsh’s most celebrated portraits) you could immediately see that Hemingway’s eyes were out of focus - the actual plane of sharpness was somewhere forward in Hemingway’s beard and his fisherman’s sweater. It spoiled the picture for a moment ... and then I backed away from the print and let myself enjoy it!

I was pleasantly surprised to find a depth of field calculator on a free light meter app I loaded onto my phone.
Plug in lens info, near/far settings you desire and it will give an f stop and the hyperfocal distance setting. Just like my 60 year old Hasselblad or Rolleiflex.
Giant leap forward.

If the goal of your post was to push readers to streaming music sites to toss Neil Young's hat three hundredths of a cent then you've succeeded without a doubt. My goodness, what an album

Mike said It's tempting to make blanket condemnations that begin with "photographers these days...,"

From my POV Circle of Confusion has nothing to do with optics.

Recently someone on a forum asked how to calculate exposure for a crop camera. He was using a hand-held light-meter, and thought that there must be an exposure equivalency formula 8-0

I answered that f/2.8 is always f/2.8. You can easily guess what kind of storm that created 8-)

With regard to your comment about viewing size, I made the mistake of getting myself a 4K monitor. Is bigger always better? That is around 8Mpixels of display. There is nowhere for my mistakes to hide! With some of my older pictures, hitting 100% on the zoom slider actually causes them to shrink.

Your observation "Many is the time I'm tempted to leave a comment on some poor stranger's picture saying, "you do realize this entire picture is out of focus, right?"" hit home with me. One of my favorite pictures, a low-light portrait of one of my god-daughters, is mostly out of focus. I spent countless hours trying to print it as visualized before I came to accept that I simply missed the focus.

Getting the focus and depth of field can be a challenge and as you say it's always been an issue to contend with. I have shot a fair amount of large format film cameras, most 4x5 and some 8x 10. I have made lots of 8x10 prints from those negatives in the darkroom which look plenty sharp. I have also scanned many of those same negatives, while examining them at 100% on the computer quite a few had noticeable out-of-focus areas, even though I thought I had used sufficient depth of field to cover the areas that I wanted to be sharp. I guess the thing is at one time those "out-of-focus" photos looked just fine unless one was using a magnifying glass to examine them (which I never did).

I have 2 thoughts:

1. A question to everyone: do you use DOF Preview on your camera? For the reasons Mike mentioned, it’s a very crude approximation. Does it mean we should only use 1:1 review to judge sharpness after fact? But I still use dof preview (on my mirrorless) to judge the dof in the context of the overall composition, something hard to do with 1:1 review zooming all the way in.

2. Question to Mike: you haven’t mentioned viewing distance. Doesn’t it negate the enlargement factor? Eg. A billboard will look not in focus 1m away but look fine 20m away.

[It just seemed like a different subject. Blog posts are tidbits, snippets; you can't fit everything in every one. --Mike]

I've commented more than once on this site that super fast lenses have always been near useless for me, as a commercial/ advertising photographer. I don't want to pay for f/0.95 lenses when I shoot mostly at f/5.6 (on 35mm) in order to get everything I want to be in focus, in focus!

When I select a prime lens for a particular photograph I'm taking, I'm thinking multiple things. How much I want to be in focus, dependent on the clients needs, what I want IN the actual photo, the compression or expansion of the scene, the "effect" that the lens will create; for environmental portraits: how much of the surrounding area needs to be discernible. One of the reasons I've always loved M4/3rd's, is that I can also select the aspect ratio of the photo, something I would have selected in the past by selecting the camera. (it's amazing to me with the new Nikon Z, that you're limited to less formats on the lower priced models, and more on the upper, when this is not a cost factor at all; this is a 'marketing price push').

You are correct, tho. Nothing is uglier than seeing "wide-open" photos where nothing is in focus, or worse, head shots where the eyes are in focus, but the tip of the nose is not. These are people that don't know what they're doing. It's easier to shoot a head shot, in most cases, with more of a distance to the background, than getting everything on the face in focus with a wide open f/stop.

On one hand, you’re absolutely right. Period.

On the other, about the picture of the woman on the beach: maybe the photographer knew that the picture was slightly out of focus but posted it anyway because he/she knew that no one is ever going to see it at 100% (let alone print it).

I suspect many pro photographers share their work exclusively online and have learned that they can widen the margin of error, based on where their target audience is going to see the pictures (mostly cell phone screens and poorly calibrated monitors).

Degree of Enlargement: As a photographer it’s nice to be able to drill down into a high rez image on a sharing site to see what’s what…but for the average viewer it’s probably best to present finished work at a specific resolution. The average viewer in a screen centric world doesn’t need to look behind the curtain and see the source material used to present the final image.

Recently I’ve been tinkering (pandemic ponderings) with printing files I originally saw as second-rate due to the necessity of an extreme crop or even motion blur. I find that with some effort I can produce nice prints from these files and I wouldn’t want my final prints to be assessed based on how my less than perfect source files appear.

“There's more to the picture than meets the eye. Hey hey, my my.” – Rust Never Sleeps

[Yes. For example, I have my cellphone pictures printed small. They just look like good prints that are small; there's no reason a viewer needs to know that they won't print large. --Mike]

What? You don't like "boker"?

Next, please address "filmasturbations", I mean "film discolorations". You know, "film simulations".

Or even worse, filmposers who claim to like the flaws in actual film that the manufacturers struggled so mightily to get rid of.

Yes, I am a curmudgeon.

And to those who whine about the loss of motor noises with the advent of electric cars: Nope. If it's not a Colombo V12 or a Mezger flat 12, then never mind. And those flat-crank V8s are just ugly noise.

If it's not an 8x10 or larger contact print, then Nope. Forget film.

Hi Mike,

Yes. And more like this please: effective reminders of core elements of photography.

The actual discussion is not just about bokeh. It's about display of an image. It's not just focus/out of focus differences that show up with output size and viewing distance, so do many other things, like the visibility of noise.

Unfortunately, most of the Internet seems to think that camera makers should pursue "perfect" results at the maximum imaginable size, which seems to be infinity ;~). Which, of course, is impossible.

And in video, we have another related issue: every distributor/producer wants to know that their video will survive the next few boosts in "resolution." So we have people shooting 4K for 1080P output, and now 8K. 16K is coming, so all that earlier work will be "ruined" someday.

Sharpness is a bourgeois concept. I kid. Using a wide aperture has been imprinted on my photographic mechanism, but this is from the days of film and tending to shoot in dingy light and long before I ever heard of the term bokeh. In any event, I need to look after this tendency or it will take over.

I cannot think at high capacity when taking photos so I do two things. I always reset to f8 and then adjust from there as needed, and for DOF I think to myself, the subject should have as much focus as it needs but not more (if the subject is the relation to foreground to background then I need a lot).

Since photography is a game of paradoxes you need to remember that as you get closer the subject needs more DOF from your aperture setting not less. Reviewing DOF charts is an eye opener. 5 feet away with a full frame 50mm at f4 your DOF is a little over 8 inches.

I think this is why there are a lot of photographs with bad focus online. Plus on tiny Instagram versions of photographs it hardly matters.

I believe the famous Migrant Mother and Daughters photo by Dorothea Lange is slightly out of focus as well. The back of the children's heads are tack sharp but the mother's face is soft.

What ever happened to f-32?
I had a 105 Nikkor that offered it, but on everything else the stops stopped at 22, or God forbid, 16.


Well maybe I've missed some of that, but... (and this isn't important, just commenting), I do think, after reading your column, that DOF is a fixed property of a lens. You've shown that it's definitely not a fixed property of the whole 'delivery system'. Is there some part I didn't get where you talk about the lens itself changing it's DOF?? I'll go reread again, but I'm not seeing that. Thx.

When I switched to digital in 2005, I started to use only f8 am f11. Obsessing with max sharpness. A few years later. In fact, too many years later I realized how silly this was. Now I just use the aperture that I think suits the picture most. And use the whole scale from f1.4 to f32. Quite liberating. And the only ones that will notice the difference, if anyone at all, is photographers that manage to push their nose 5cm from the print, and 5cm up their own behind at the same time.

Question: how does film/sensor size change the transition from sharp to out-of-focus?

Pedantry: Bokeh is the quality of the blue, not the quantity of it. The effect is probably not important, and certainly not as important as some make it, unless for a particular image, it is. I have an old medium-format Jena Sonnar (180/2.8) that I adapt to my Pentax 645z, and it is not super sharp or contrasty, but the slight residual spherical aberration makes those out-of-focus details fade beautifully together. For some subjects, that's just the ticket.

Shooting and getting it sharp at maximum aperture ("wide open") was a selling point for Leica lenses. People paid for that privilege and performance.

With the others, the maximum aperture tend to be ceremonial and it was customary to stop down 2-3 stops before appreciable sharpness was obtained.

Today, you can buy a new 50/1.2 lens for less than $100. Whether it performs depends on what you expect in a performance. But one thing is certain - there are a lot of bragging rights to have that kind of glass mounted on your camera.

I'll blame a slavish dependence (a fetish?) on always shooting wide open. Sometimes, f4 is better. And nice, too.

Today's lens design, and the attributes of digital image capture, emphasize narrow planes of focus, and dramatic focus falloff. Which is fine, but you still need to use your aperture ring (dial!) properly for your subject.

What drives me crazy is that while in almost all lens reviews there is a section about bokeh, it inevitably only shows pictures taken at the widest aperture. For practical shooting I'm more interested in the look of the oof areas stopped down. For instance, I often shoot a 35mm lens at around f/4 or f/5.6 (and BTW haven't so far found one that matches the bokeh qualities of the legendary Leica Summicron-M 35/2 IV).

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