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11-12-2012, 04:34 PM - 9 Likes   #1
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DoF is worthless!

Why oh why do I keep seeing weird arguments about "depth of field" (just as a concept).

It appears when people talk about fast lenses.
Why buy a fast lens? For a thinner DoF, of course!
No! No, you buy a fast lens so you can get more light, so you can shoot in darker conditions, so you can use faster shutter speed, so you can use lower ISO, because fast aperture on a lens is often indicative of good overall lens performance, because you can always stop down but you cannot open beyond the max. There are many reasons to get fast lenses, but DoF should NOT be among them. First of all, the difference between f2.4 and f1.7 is not big in terms of DoF. It is a big difference in regards to light captured, though.

It appears when people talk about APS-C vs FF.
Why FF? Because you get a thinner DoF, of course!
No! Stop it! Yes, FF can have its perks. Yes, FF tends to indicate a higher quality camera (not anymore, not really, but let's pretend). Valid arguments are about noise performance, AF, wide angle capabilities, etc. But not about DoF. Even worse, here people start talking about DoF equivalence, as if the DoF is the most important thing and everything else, aperture, shutter speed, ISO, is just centered around making the thinnest possible DoF. Please, people, stop this. FF has its pros and cons, as does APS-C. DoF is the least important thing.

Thinner DoF means better photos!
No, it does not. Making a portrait with a thin DoF can be useful, but if it is too thin it becomes distracting. The person's eyebrows and nose are suddenly out of focus, the surroundings turn into mush, suddenly the photo becomes a mess of blurry bits instead of a portrait of a whole person. Portraits are more than just the eyes! It is not romantic, it is not sexy, it is not "deep" to take photos with overly-sharp and saturated eyes, with everything else being blurred out.

Can DoF be used creatively? Sure. Just as split toning and HDR. But please, calm down with the DoF. It is not that important, ever. Nobody will look at your photo and say "this is garbage, but it would be good if you had 2mm less stuff in focus." A lens at f2.8 and f1.4 will not have a big difference in DoF with near focusing. I often shoot wide open, but usually it is to gather more light, to allow faster shutter, or to have a more pleasing OoF bokeh (since aperture blades don't turn it hexagonal, so a slower lens can be useful because it has a wider DoF and round bokeh), not because I am hoping the DoF will be thinner.

Here are examples of my usage of thin DoF:
500px / Photo "Flower solitude" by Stolpulus II
500px / Photo "Magical mood" by Stolpulus II
Notice that these have ISO 1600 and one is still dark. And notice also that the photo would be better if the DoF were wider, if more stuff would be in focus.
Extreme subject isolation is rarely useful, but often it is distracting. But I also find myself sometimes shooting "wide open aperture in bright sunlight to make an artistic photo." Those photos are rarely any good.

And yes, I know DoF is related to aperture, how nearby you are focusing (which is usually related to what focal length you are using), even to sensor size (in some convoluted, mathematical way), but people keep talking about it as if it is the one most important thing. More important than ISO performance, than DR, than AF. It is not. Of all the variables in photography, DoF has to be one of the least important. The exception being maybe landscape and street photography where you usually want the exact opposite - maximum DoF. And tilt-shift is not helping with its "miniatures" gimmick. Shift lenses were usually used to improve the sharpness, to get more stuff in focus, not less. The miniatures effect is just a funny addition, its not the reason to buy shift lenses/adapters.

If you want more blur, just buy a "soft" lens or put vaseline on a filter. I don't know why thin DoF has become such a fetish among so many photographers. Its probably related to expensive, fast primes being so sought-after and a status symbol, rather than just a tool. Hey, I'd like a f1.2 lens for Pentax, I'd use it in the dark. And I wish Pentax had some more faster lenses, but I want light and quality, not DoF.

Ugh, I had to write this rant, I had to vent a little

11-12-2012, 04:43 PM   #2
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Common sense in a rant. Well written.
11-12-2012, 04:49 PM - 4 Likes   #3
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But how else could you get a photo like this?

11-12-2012, 05:20 PM   #4
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QuoteOriginally posted by boriscleto Quote
But how else could you get a photo like this?
Ah the difference between priceless and worthless. Brilliant image to post.

11-12-2012, 05:43 PM   #5
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I'll share a few of what I consider appropriate use of F1.7











11-12-2012, 05:56 PM   #6
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QuoteOriginally posted by Na Horuk Quote
.... DoF has to be one of the least important.
For you, perhaps. For others, maybe not.
11-12-2012, 06:04 PM   #7
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Shallow DoF is not going to help me with this shot which is already at f3.2... (a wedding photo)
So, I agree with the OP, not every shot has to have shallow DoF...

I just noticed that I can get moire by shrinking the photo..

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11-12-2012, 06:06 PM   #8
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I tend to use DoF a lot for my shots, but honestly its more of a matter of how the lens acts wide open (bokeh, aberrations, etc) as opposed to the size of the DoF.
11-12-2012, 06:08 PM   #9
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QuoteOriginally posted by boriscleto Quote
But how else could you get a photo like this?
That site really makes me wonder if some of these people are actually getting paid for this stuff.
11-12-2012, 07:21 PM - 1 Like   #10
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The more I think on this, the more I have to disagree.

For macros, portraiture and some still life/nature kinds of shots, DoF is *everything*. If you have a busy background, you'll want to isolate it, and do so with a minimum of fuss and bother. Knowing how the DoF behaves on a particular lens means being able to frame and isolate a subject and render the rest into some degree or another of OOF bokeh.

For some subjects, you want that hair-thin effect otherwise the surrounding clutter will utterly detract.

Poking through what I have on Flickr, I have a number of shots that depended upon use of the DoF to get the results I was after.

In this shot I was after the spike and its shadows. I wasn't interested in the sky, or the trees, or the busy street behind it, nor the foreground. Enter a need for knowing the DoF (in this case from a Sears 28mm macro shot wide open at 28mm).



This time, I was deliberately shooting for the bokeh in the shot. Shot stopped down, it would of been a cluttered mess.
DA18-55, shot at 40mm @ f/4.5



Again, I needed to isolate the nutcracker from the tree behind it. Enter needing to use a lens that I knew I was going to throw the background into a blur via controlling the DoF properly.

50mm, f/1,7



Again, I was aiming for a portrait of my son. I didn't want a portrait of my son with a bunch of lines from washing machines and driers in the background. I *did* want my hand to be at least somewhat in focus because thats the kind of shot I was going for at the moment.
DA 18-55mm, 35mm @ f/4.5



This one was just a test shot at the time, but I was trying to figure out my white balance and the like. I was shooting for the leaf - not the hillside and trees behind it. Knowing how my Sigma 70-300 behaves with the DoF gave me this.



And this.



So unless all you're interested in are flat photos shot with really narrow apertures with everything in focus (Hey, I can do this with my point and shoot!) Depth of Field plays into *everything*. Whether you're using it or trying to avoid it, its one of the prime bits that come into play in every shot you take.

You may not buy a lens for its DoF, but anyone with an SLR worth their salt had better learn how that lens treats its DoF fast in order to use it properly.

Granted, thats just my 2 cents on the subject.
11-12-2012, 07:48 PM   #11
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IMO, depth of field is just another variable that one has to deal with depending on the situation and desired effect.

Most of us will agree that having a lens capable of a thin DOF and decent bokeh is extremely useful and highly valuable...but that doesn't mean that all (if any) picture needs to have the thinnest possible DOF, for example, a group portrait.

I would say that, all other things being (which is not always the case), having a lens with a larger aperture is always better because, when stopping down, you can get more sharpness at a larger aperture (vs a lens with a rather limited max aperture).
11-12-2012, 08:03 PM - 5 Likes   #12
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DoF is an excuse for needing full frame as far as I can tell. My students had to shoot for shallow DoF using point and shoots. And they all got that assignment done. It isn't rocket science. And I'm sure many of them never got DSLRs and continue producing narrow DoF shots with their point and shoots. No one ever taught them they had to have a specific type of camera to do it. The laws of DoF are the same for any sensor. The wider your lens is, the closer your subject has to be and the further away you back ground has to be. Despite what many will tell you, format has nothing to do with it.

The issue that could easily be discussed, of which DoF is a part is subject isolation.

There are many ways to isolate your subject... not all involve DoF.

Colour contrast...




Placement in the image...





Sometimes just the fact that the subjects fill the frame creates separation.



Often a scene would be ruined by having narrow depth of field.





In this shot the textures create the isolation.


IN this shot it's the tonal contrast that creates isolation




If DoF is the only way your images create subject isolation, your photography is going to get old real quick. it's part of the package, and it's not necessary to even have that fast a lens to do it. You just have to know how to use the equipment you have to achieve the effect you want.

Last edited by normhead; 12-31-2014 at 07:21 AM.
11-12-2012, 08:35 PM   #13
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QuoteOriginally posted by normhead Quote
You just have to know how to use the equipment you have to achieve the effect you want.
Agreed, and a nice visual essay too.

One also has to be alert to the danger of bokehing everything to death becoming a photographic cliche. It may be too late for that, I think.
11-12-2012, 08:37 PM   #14
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QuoteOriginally posted by normhead Quote
DoF is an excuse for needing full frame as far as I can tell. My students had to shoot for shallow DoF using point and shoots. And they all got that assignment done. It isn't rocket science. And I'm sure many of them never got DSLRs and continue producing narrow DoF shots with their point and shoots. No one ever taught them they had to have a specific type of camera to do it. The laws of DoF are the same for any sensor. The wider your lens is, the closer your subject has to be and the further away you back ground has to be. Despite what many will tell you, format has nothing to do with it.

The issue that could easily be discussed, of which DoF is a part is subject isolation.

There are many ways to isolate your subject... not all involve DoF.
Well written. Thank you.

And thanks for the well done examples.
11-12-2012, 09:28 PM   #15
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QuoteOriginally posted by Na Horuk Quote
Why buy a fast lens? For a thinner DoF, of course!
No! No, you buy a fast lens so you can get more light
Unless, of course, you buy it to get better control over selective focus...


Steve
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