Depth of Field (Bokeh) lesson

[The_Traveler]

The entire thread - tldr

 

[snowbear]

The entire thread - tldr

Summary:
DOF,
Bokeh,
Sensor Size,
Confusion Circles,
Popcorn

 

[Derrel]

This thread was originally about depth of field and, ostensibly, about bokeh. I think unfortunately, the original post might not have been created so as to create much of a fruitful discussion. Depth of field and bokeh are, really, two very different subjects. Very,very,very different subjects.

Bokeh, as in the out-of-focus areas of a photography--I gave a good reference to the Americanized word bokeh, from the actual web-blog post written by the original magazine editor who introduced the Japanese word boke to the English-speaking world, but with an "h" added to the end of the Japanese-language word, so as to prevent bad pronunciation of the word, way back in the 1990's (Hint: bokeh does not rhyme with toke,or joke, or smoke).

Unfortunately,for the most part, the subsequent replies to the original post have in some cases, devolved into mathematically-based examples of a most unhelpful nature, with very little emphasis on bokeh, or what it is, or what it looks like.

As to the questions, "Is there any usefulness to DOF from the hyper-focal distance to infinity? is that an area where I am likely to look at in a photo?" The answer to those two questions, I would think, are pretty self-evident, as an emphatic "Not much", and, "Not very likely."

If ever there were a TPF thread that ought to be closed, soon, this one qualifies. Split depth of field up and separate it, from the subject of bokeh. Go back to the actual SOURCE material on bokeh, and stay away from the Wikipedia definitions of it; as Mr. Johnston himself has written about the entire subject of bokeh, his very own words on the subject of bokeh, have on numerous occasions, been re-written by Wikipedia's so-called "experts".

 

[Ysarex]

Because that's what the word compare means. Duuuuh. An analogy: Let's compare the suitability of two different woods; poplar and cherry. Let's use the cherry to make a musical instrument -- a wooden flute, and the poplar to make a kitchen cutting board. And now we compare the suitability of the woods. Can you see where we went wrong?

You still don't get it do you? You're saying y=x but in your proof you're specifying that the condition y=x must be met to be a valid comparison. I'm not making kitchen boards out of sugared cherries but explaining the flaws in your theory because you seem hell bent on linking smaller sensors to greater dof when all the evidence says it is the smaller effective aperture diameters that create greater dof, the smaller sensors do not always have greater dof.

I never said smaller sensors always have greater DOF. Show me where I said that. You're arguing with the words you put in my mouth.

Of course dof calculators account for sensor size!!!

c is directly defined by dividing the finished print size by the sensor size, that's how you calculate c! But please note that the smaller the sensor then the less dof for any given COC, by your very own maths as you've presented???

Yes, the math requires an accommodation for sensor size. That's all I ever really said: "Don't forget the size of the recording media. All else held equal to take the same photo with cameras of different sensor size, there will be a DOF difference due to sensor size." You can't do the math and calculate DOF without including the size of the sensor and so sensor size is a factor in determining DOF. When used to take the same photo the smaller format camera will produce deeper DOF.

This fact that the smaller sensor camera produces deeper DOF when used to take the same photo is appropriate as a general rule. And this is what matters to photographers. Photographers take photographs and if they're comparing cameras they want to know how they'll perform when used for the same application.

I completely understand that a smaller format camera REQUIRES shorter lenses in general use. That set to the same f/stop the effective aperture diameter of a shorter lens is smaller than a longer lens. I get that. But the fact that smaller format cameras do REQUIRE shorter lenses in order to have generally useful fields of view means that smaller format cameras generally take photos with deeper DOF than larger format cameras.

This is true: Smaller format cameras generally produce photos with deeper DOF when compared with larger format cameras.

This is true: Give an Olympus Pen m4/3 camera to photo group A (5,000 people) and a Nikon D800 to photo group B (5,000 people). All participants are instructed to take 10,000 photos in a month of the "world that surrounds them." All live similar lives. They go to work, they spend weekends with the family, etc. etc. All participants are free to use lenses as they see fit but are reminded of the instruction to take general photos that depict their world. Compare the 50,000,000 photos as a whole from each group and in general the photos in group A will exhibit deeper DOF than the photos in group B.

And because that's true I'm going to continue to affirm this: You can't do the math and calculate DOF without including the size of the sensor and so sensor size is a factor in determining DOF. When used to take the same photo the smaller format camera will produce deeper DOF.

My rationale for presenting this in this form is because it is useful and helpful for photographers. "All else held equal to take the same photo with cameras of different sensor size, there will be a DOF difference due to sensor size."

Joe

 

[robbins.photo]

the circle of confusion is in my head.


i am the walrus.


coo coo ka-choo.


just out of curiosity, (and since i have been totally lost since math was introduced into the conversation) is there any usefulness to DOF from the hyper-focal distance to infinity? is that an area where I am likely to look at in a photo?

Hi, Eggman here...

So, reading through all of this.. er, well reading through some of this and just skimming over the charts and graphs and the pictures with the circles and the arrows and such...

It occurs to me that whenever anyone uses the term "bokeh" they almost always use it incorrectly, or at the very least they don't take the time to put in a 45 page dissertation explaining precisely what they mean by using the term.

Then someone else comes along and in an effort to prove their superior subject knowledge, just can't resist the impulse to offer a correction. That correction is then corrected again and before you know it we've got a knock down drag out on our hands. Charts and graphs are flying everywhere... dogs and cats living together. Basically the worst parts of the bible.

Ok, so for the folks that are arguing the EXTREMELY FINE points here, just stop and ask yourselves, do you honestly think any of this is any way really useful or even understandable to the average photographer in the field? If you really believe that, can you post a simple, one paragraph explanation of why without using any charts, graphs or equations?

If not, then maybe it's time we all put our professor hats away and move on.

This has been a community service message from your local Eggman.

 

[Tim Tucker]

Yes, the math requires an accommodation for sensor size. That's all I ever really said: "Don't forget the size of the recording media. All else held equal to take the same photo with cameras of different sensor size, there will be a DOF difference due to sensor size." You can't do the math and calculate DOF without including the size of the sensor and so sensor size is a factor in determining DOF. When used to take the same photo the smaller format camera will produce deeper DOF.

This fact that the smaller sensor camera produces deeper DOF when used to take the same photo is appropriate as a general rule. And this is what matters to photographers. Photographers take photographs and if they're comparing cameras they want to know how they'll perform when used for the same application.

And I'm saying that there are too many examples where this is not true for it to be held as a general rule. The rule that dof is proportional to sensor size only really works of the same photo example (same fov, same subject distance and same f-stop) and only holds valid at portrait distances.

Below are some examples of an actual photos of many I have to illustrate the point because it's common in landscape photography. I will continue to use your same photo example (same fov, same subject distance and same f-stop) to show you where it fails and where smaller sensors do not produce greater dof.

Please consider your same photo example because the same photo with a smaller sensor does not produce a deeper dof with these photos, it produces the same dof. You do not get a deeper dof with a smaller sensor across the full range of focussing distances and f-stops. The rule has very real and practical limitations.

But, and it is a big but, it would be true to say that if you were to take the same photo, (same fov, same subject distance), but this time say same dof, then the photo on the smaller sensor will always be shot using a wider aperture, (except macro of course).

This always has been the advantage of smaller film formats, and still holds true at base ISO. In the samples below I would not get greater dof with a smaller format, but I could take the same photo in the same light at a faster shutter speed and so you can use hand held in a greater variety of situations then you can use the larger formats. I could've taken some of them without a tripod.

"All else held equal to take the same photo with cameras of different sensor size, there will be a DOF difference due to sensor size."

Only holds true under certain conditions and through a limited range of focus distances and f-stops. There is not always a dof difference due to sensor size. Why try an re-invent the wheel and relate things to sensor size when there are perfectly valid principals that do hold true?

Sample photos. The last one was taken with a 55mm lens and is a pano at fixed manual focus, the others an old 35/2 MF lens:

 

[Tim Tucker]

Ok, so for the folks that are arguing the EXTREMELY FINE points here, just stop and ask yourselves, do you honestly think any of this is any way really useful or even understandable to the average photographer in the field? If you really believe that, can you post a simple, one paragraph explanation of why without using any charts, graphs or equations?

See above.

 

[robbins.photo]

Ok, so for the folks that are arguing the EXTREMELY FINE points here, just stop and ask yourselves, do you honestly think any of this is any way really useful or even understandable to the average photographer in the field? If you really believe that, can you post a simple, one paragraph explanation of why without using any charts, graphs or equations?

See above.

Ok, so you want me to follow through all this high end math and you can't even differentiate between 1 paragraph and 6?

Hmm...

Also, nothing in your explanation really tells anyone why any of this incredibly fine hairs your attempting to split matter at all to your average joe photographer. Can I get the same DOF from a smaller sensor than I can from a larger sensor? Under the correct conditions, sure.

Do I need 47 pages of charts and graphs to realize this? Nope. Do I need a 5 1/2 hour lecture on circle of confusion to understand that... not just no but hell no.

Ok, so maybe we can all just agree that:

1. When someone uses the term bokeh since we all know what they actually meant nobody has to be Mr. Wizard and explain it down to the gnats behind, because frankly it's not really of any use to anyone. If they are using the term incorrectly, just direct them via weblink for the 450 page dissertation you like best in explaining it and leave it at that.

2. We can acknowledge that DOF is influenced by several factors and worry about folks that may not understand that gaining a basic understanding of HOW THAT APPLIES IN THE FIELD, rather than every time someone dares use the term bokeh getting dragged into one of these hypertechnical arguments that frankly serve no real purpose. Lets be honest, they probably confuse most folks far more than help them.

 

[Tim Tucker]

Ok, so you want me to follow through all this high end math and you can't even differentiate between 1 paragraph and 6?

Hmmm...

Do I need 47 pages of charts and graphs to realize this?

Differentiate between 5 pages and 47?

As to your general comment, no I do not know how many actually understand it. We may have gone a little deep in places for a beginners forum but there were a lot of basics in there. And though we will check the boring bits you don't wish to see I don't think it fair to criticise us and over-dramatise what was a healthy discussion that may actually persuade some photographers to learn a little more from other sources.
The space is here, people ask questions and are willing to read, why should there be censure about what they can and can't read if we stay on topic and are civil?

We'll stop now and go back to making comments about popcorn.

 

[robbins.photo]

Ok, so you want me to follow through all this high end math and you can't even differentiate between 1 paragraph and 6?

Hmmm...

Do I need 47 pages of charts and graphs to realize this?

Differentiate between 5 pages and 47?

As to your general comment, no I do not know how many actually understand it. We may have gone a little deep in places for a beginners forum but there were a lot of basics in there. And though we will check the boring bits you don't wish to see I don't think it fair to criticise us and over-dramatise what was a healthy discussion that may actually persuade some photographers to learn a little more from other sources.
The space is here, people ask questions and are willing to read, why should there be censure about what they can and can't read if we stay on topic and are civil?

We'll stop now and go back to making comments about popcorn.

Well, slightly more condescending than your normal fair, but I guess no point in feeding into you and the other professors incessant OCD on the topic.

Frankly you've all gone way off the deep end, as you always do, whenever this topic comes up. I think you realize that, thus the need to obfuscate and scream censorship. I was just hoping maybe you and some of the others would clue into the fact that when more than a few of the regulars here start questioning the usefulness of what is being posted/argued about that should give you pause to reconsider.

Or I guess you could just leave your professor hat on and continue to lecture to an empty classroom. Whatever floats your boat I guess. Have fun posting your charts and arguing moot points for no apparent reason.

I'm sure there's a veritable flood of people researching the topic in depth even as we speak thanks to the fascinating and scintillating "No your wrong, no your wrong" approach taken thus far.

Still waiting on you to offer a simple explanation as to why any of this would matter to your average photographer, or what benefit it would be to capturing better images. Lets just say I won't hold my breath.

 

[pixmedic]

nice shot

 

[OGsPhotography]

I like my Bokeh after a "good" depth of field.

 

[snowbear]

I talked to my bokeh about the fifth at Pimlico. Oh, wait, that's bookie. Never mind.

 

[Ysarex]

Yes, the math requires an accommodation for sensor size. That's all I ever really said: "Don't forget the size of the recording media. All else held equal to take the same photo with cameras of different sensor size, there will be a DOF difference due to sensor size." You can't do the math and calculate DOF without including the size of the sensor and so sensor size is a factor in determining DOF. When used to take the same photo the smaller format camera will produce deeper DOF.

This fact that the smaller sensor camera produces deeper DOF when used to take the same photo is appropriate as a general rule. And this is what matters to photographers. Photographers take photographs and if they're comparing cameras they want to know how they'll perform when used for the same application.

And I'm saying that there are too many examples where this is not true for it to be held as a general rule. The rule that dof is proportional to sensor size only really works of the same photo example (same fov, same subject distance and same f-stop) and only holds valid at portrait distances.

Wrong.
One more time: A comparison makes no sense when you don't compare like objects. (My medium format camera takes photos with deeper DOF than your phone camera. Look here's a photo of the Grand Tetons and it has deeper DOF than your phone camera photo of a bee on a daisy! Proof!) There are two possibilities here for like objects. 1. The same photo. 2. A large average group of average photos. In either of those two comparisons use of a smaller format camera will produce deeper DOF results all else held equal. This is common photographic knowledge and has been for a long time:

DOF Master says you're wrong. (Note the CoC value is reduced for the crop sensor camera. Sensor size as such is incorporated into the math calculations.)

Leslie Stroebel says you're wrong. View Camera Technique (page 130 5th edition).

The general rule that smaller format cameras produce deeper DOF does not apply only to portrait distances. It applies as a general rule for all distances. Obviously you can take a photo as in the 2nd example below where you have the DOF limits extending across the entire image -- I only needed to turn the APS camera horizontal and re-focus or stop the lens down further to do that. That does not negate the general rule, it simply means there are usage conditions in which it is not critical.

Joe

 

[The_Traveler]

Excuse me, I just got an offer to have a colonoscopy and a root canal simultaneously.both without anesthetic and that sounds better than reading any more of this discussion.