is the depth of field suppose to be subtle?

RAZKY

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This is incorrect. It's a common myth that you can factor out lens focal length. In some cases you can but in other cases you can't. Interesting that you provided a link to a macro DOF calculator. In closeup and macro work it is possible to factor out the lens focal length so that DOF will = magnification + f/stop. But that won't necessarily work if you're shooting landscapes. Consider the example below using DOFMaster's calculator. You're going to have a tough time making the argument that 127 feet = 28 feet.

View attachment 246114
As unpopular notes, this can be baffling. I plugged the same information for each lens as you did into the macro calculator, and in both cases the results were identical - scale of reproduction is 1:128.6, total depth of field is 26.26 feet, at f/8.0. As near as I can tell, that depth of field agrees closely with the DOF scales on my lenses.
I think that the macro calculator is useful for anything from, say, 1:10 to beyond 1:1000.
 
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Ysarex

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As unpopular notes, this can be baffling. I plugged the same information for each lens as you did into the macro calculator, and in both cases the results were identical - scale of reproduction is 1:128.6, total depth of field is 26.26 feet, at f/8.0. As near as I can tell, that depth of field agrees closely with the DOF scales on my lenses.
I think that the macro calculator is useful for anything from, say, 1:10 to beyond 1:1000.
Unpop noted that the existence of the myth that focal length can factor out of DOF can be baffling. DOF has been well understood for a very long time. As for Unpop's bafflement I think the explanation is the rate of misinformation spread on the Internet. It wouldn't take but a minute to compile a large collection of myth spreading youtubes: Got to love this one that the author even titled DOF Myths:
-- he's telling you up front he's about to misinform you. (And he is wrong in that video so if you watch it know that you're being misinformed).

Your macro calculator is just that and it most likely uses macro specific math calculations. We know that focal length does factor out in the macro range where the DOF distribution around the focus plane is close to 50/50. Given that we can simplify the math without error. But those calculations aren't correct outside the macro/close focus range.

I used DOFMaster in my post above: Online Depth of Field Calculator
The calculator at Cambridge in Colour is also good: A Flexible Depth of Field Calculator
And this DOF calculator/simulator is also good: DOF simulator - Camera depth of field calculator with visual background blur and bokeh simulation.

They will all agree with the figures I got from DOFMaster. Look at the illustration I posted and note that DOFMaster presents values in each case for hyperfocal distance for the f/stop in use. Compare for each lens the hyperfocal distance with the focus distance and there's you explanation for why you can't factor out focal length as a DOF determinant variable in all cases. The rate of DOF increase is not constant and increases approaching the hyperfocal distance.

The myth you picked up comes from the fact that magnification is a function of focal length and subject distance. Since focal length and subject distance are both variables in a DOF calculation can't we just factor them out and replace them with magnification -- simplify the equation? That'll work for bugs on flowers but not for a mountain stream framed beneath the Grand Tetons.
 
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ntz

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let me tell it short ... it's not science .. @Ysarex tends to think about things scientifically, that's not bad, it's his way ... the most of us others just feel it after some time ... there are two important factors

1) know your gear, every lens is bit different
2) learn to implicitly think about DoF before you will take the photo, predict it before you press the shutter button, then correlate with outcome, it will just settle in your head and those calculations and predictions will be automatic and more accurate ..

there is simple formula - the longer focal length X bigger AP X closer subject makes more bokeh .. for example in shot below I wanted absolute bokeh on the background so I've shot with 70-200mm f/4 lens on 200mm and f/4 without thinking expecting exactly this result (well, it even surprised me a little, not level but final look in real ;))

full
 

Ysarex

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let me tell it short ... it's not science .. @Ysarex tends to think about things scientifically, that's not bad, it's his way ... the most of us others just feel it after some time ... there are two important factors

1) know your gear, every lens is bit different
2) learn to implicitly think about DoF before you will take the photo, predict it before you press the shutter button, then correlate with outcome, it will just settle in your head and those calculations and predictions will be automatic and more accurate ..

there is simple formula - the longer focal length X bigger AP X closer subject makes more bokeh .. for example in shot below I wanted absolute bokeh on the background so I've shot with 70-200mm f/4 lens on 200mm and f/4 without thinking expecting exactly this result (well, it even surprised me a little, not level but final look in real ;))

full
Very nice photo. But you're repeating another very common myth -- bokeh is not out-of-focus background. It's the character of the out-of-focus background as a function of the lens used. Here's some help with very good visual examples: Kiev Cameras
 

unpopular

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To second Ysarex, ‘acceptable focus’ is defined where the resolving power of the imaging system is less than the diameter of the circle of confusion (in this context I am referring to CoF as the projected image of the aperture that make up the image - lovingly referred to as ‘bokeh balls’ when sufficiently large enough and with enough contrast to be individually discernible)

Each of these qualities are measurable, and I think it’s important to understand the science, even when ultimately we use intuition.
 

ntz

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Very nice photo. But you're repeating another very common myth -- bokeh is not out-of-focus background. It's the character of the out-of-focus background as a function of the lens used. Here's some help with very good visual examples: Kiev Cameras
thank you mad professor :)
 

RAZKY

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Unpop noted that the existence of the myth that focal length can factor out of DOF can be baffling. DOF has been well understood for a very long time. As for Unpop's bafflement I think the explanation is the rate of misinformation spread on the Internet. It wouldn't take but a minute to compile a large collection of myth spreading youtubes: Got to love this one that the author even titled DOF Myths:
-- he's telling you up front he's about to misinform you. (And he is wrong in that video so if you watch it know that you're being misinformed).

Your macro calculator is just that and it most likely uses macro specific math calculations. We know that focal length does factor out in the macro range where the DOF distribution around the focus plane is close to 50/50. Given that we can simplify the math without error. But those calculations aren't correct outside the macro/close focus range.

I used DOFMaster in my post above: Online Depth of Field Calculator
The calculator at Cambridge in Colour is also good: A Flexible Depth of Field Calculator
And this DOF calculator/simulator is also good: DOF simulator - Camera depth of field calculator with visual background blur and bokeh simulation.

They will all agree with the figures I got from DOFMaster. Look at the illustration I posted and note that DOFMaster presents values in each case for hyperfocal distance for the f/stop in use. Compare for each lens the hyperfocal distance with the focus distance and there's you explanation for why you can't factor out focal length as a DOF determinant variable in all cases. The rate of DOF increase is not constant and increases approaching the hyperfocal distance.

The myth you picked up comes from the fact that magnification is a function of focal length and subject distance. Since focal length and subject distance are both variables in a DOF calculation can't we just factor them out and replace them with magnification -- simplify the equation? That'll work for bugs on flowers but not for a mountain stream framed beneath the Grand Tetons.
If I ever get bored (not likely!), I may run some careful tests with both calculators. In the meantime, I’ll continue with what I’ve used for 60+ years. For 35mm work most of my lenses have DOF scales. For ratios from 1:20 to 10:1, I use a DOF chart from about 1950 that was in the booklet for a Leica Visoflex bellows. While ratios and distances at various extensions are given in the booklet for 50, 90 and 135mm lenses, there is no mention of focal lengths in the chart - only the DOF at various ratios and apertures. (Not relevant?)
I shoot mostly 6 x 7 and 6 x 9, just focus on the ground glass with a loupe - no need for a DOF calculator there.
I mentioned the macro calculator because I only discovered a couple of years ago that, as I mentioned earlier, it agrees nearly the same as the DOF scale on manual focus lenses.
 

Ysarex

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If I ever get bored (not likely!), I may run some careful tests with both calculators. In the meantime, I’ll continue with what I’ve used for 60+ years. For 35mm work most of my lenses have DOF scales. For ratios from 1:20 to 10:1, I use a DOF chart from about 1950 that was in the booklet for a Leica Visoflex bellows. While ratios and distances at various extensions are given in the booklet for 50, 90 and 135mm lenses, there is no mention of focal lengths in the chart - only the DOF at various ratios and apertures. (Not relevant?)
Relevant as to close-up and macro work, yes. It is correct that focal length factors out of the DOF equations for macro/closeup photography. You just can't make that a blanket statement for DOF in general.

You can go so far as to say the tendency is for focal length to factor out. In a simplified form we can say that DOF = magnification + f/stop, but that has to be presented as a simplified rule with the benefit of conveying a concept, but when we roll up our sleeves and get to work it has to be a little more complicated.
I shoot mostly 6 x 7 and 6 x 9, just focus on the ground glass with a loupe - no need for a DOF calculator there.
I mentioned the macro calculator because I only discovered a couple of years ago that, as I mentioned earlier, it agrees nearly the same as the DOF scale on manual focus lenses.
 

Ysarex

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thank you mad professor :)
You're welcome -- you got the professor part right, but last time I checked I was still sane.
 
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ac12

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Sharpshooterr

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Well as I am in a rather snarky mood, and the OP here has in a good number of posts, proclaimed 'a professional understanding of photography", ima gonna have some FUUNN

4. Focus, the lens has to REFOCUS ANYTIME it CHANGES FOCAL LENGTH

Ok FlyP, I too am feeling a little snarky so maybe I’ll have a little FUUNN too!!! LoL

I own a couple of high zoot Canon L zoom lenses. Now according to you, every time a zoom changes focal length I need to re-focus?
Now that might be true if they were cheap little Varifocal lens designs.
BUT, Canon assured me that all my high zoot L lenses were of a very special design they call Parfocal and maintain focus no matter how fast I zoom them in and out. So what gives here?!
So this is where the fun starts, could you please explain exactly what that is that seems so contrary to what you stated and why MY zoom lenses maintain focus no matter how much I change the focus length??? Not all of us have a professional understanding so please use small words so we can all understand! LoL
SS
 

Grandpa Ron

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In the end I have always considered DOF to be what it to be. I am usually limited by mechanics of the scene and the aperture of the lens. Post processing has added to the mix, but I do not do much of that.
 

NS: Nikon Shooter

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is the depth of field suppose to be subtle?

That is not the right question. DoF, though, may be the right
answer when approaching the finality of a picture. There is no
law nor rule but it is all a matter of communication and taste.

For example, a documentation picture may have an ƒ11+ a-
perture while an inspirational one may do well with F2:5 or
less. The later suggesting the environment as the document
will depict it in more details and contour.

What needs to be documented or should only be suggested.
 

Scott Whaley

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ph0toe,

You have to flip the switch on the lens itself to manual. If you leave it on AF, you have to half press the shutter button and hold it there while you turn your focus ring, or hold the back button focus down while you turn the focus ring (assuming you have an electronic assist lens).

Assuming you are in single shot mode, if you pressed the focus button at 70mm and then released it, the focus will stay there until you press it again. If you change the focal length to 35mm, your picture will go out of focus until you go back to 70mm. If you want to focus at 35mm, you have to hit the focus button again.
If you are in Servo mode, and hold the focus button continuously, the camera will focus as you move the camera around.

If you want the background to be more blurry, you have to increase the distance between your subject and the background.

Steve Thomas
That's why I like the back button focus feature. It allows me to focus with my thumb & use the shutter button for light metering & snapping the shot .
 

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