Depth of field question
Mar 27, 2017 10:28:23 #
Gene51 wrote:
But so far, no one has provided the correct and complete answer, or a link to support their opinion.
Sir, I am not entirely in agreement with your statement. But, please if you have anything positive to offer, I would love to read it.
Mar 27, 2017 10:37:14 #
Chefneil wrote:
I'll bet this question has been asked many times here, but I am going to craft it to get the answer I am looking for.
I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?
I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?
As all have agreed so far, in general the approximate answer is yes. But I must add, yes at 90mm and f/11, but to be totally precise at what focus distance are you comparing them? All at infinity focus, minimum focus (that will be goofy), hyperfocal point, some average distance of say 10 feet? Lens formulas certainly do affect other lens characteristics. Not totally related actual transmission or exposure of rather different lenses can vary, say a prime to zoom actual exposure might not be the theoretical same at the same F-stop. Here we are again comparing different sorts of lenses. Anyone remember back a few weeks ago the strange demonstration involving the actual magnification of the image of a door knob where different lenses of the same focal length produced different sized images? One might think that is not supposed to happen, but it does. A few UHH members explained it to the rest of us. Seemed to have something to do with theoretical focal length vs effective or actual focal length of a lens. That was part of the explanation (focus breathing).
My evidence here, I have several "film" 50mm lenses and for all of them the distance scales are different and the IR marks are in slightly different places. And again I have a number of 35mm "film" lenses where the scales are different. So if only focal length and aperture affect or control DoF, why are the focusing scales on my 50mm lenses different if all that differs is the widest aperture of 1.4 vs 1.7 vs 2.0 vs 4 (macro). Same with my three 35mm lenses of f/2.8 and f/3.5. I have 20-some lenses and I am pretty sure comparing primes to zooms is fairly iffy with IF to helicoid as well. Your theoretical discussion of DoF may actually hold for simple symmetrical lens formulas, but I'm fairly certain that DoF is going to vary between lenses with say 6 in front of and 10 elements behind different sides of a nodal point with a doublet of fluorite elements (for one example). I'm not saying any difference would be significant.
Mar 27, 2017 10:38:54 #
Mar 27, 2017 10:46:04 #
I'm not from Missouri, but I sorta think like the mules, I want to see, touch, taste, and smell. Show me results! š¤ š¤ š¤
Mar 27, 2017 10:49:37 #
[quote=lamiaceae]As all have agreed so far, in general the approximate answer is yes. But I must add, yes at 90mm and f/11, but to be totally precise at what focus distance are you comparing them? All at infinity focus, minimum focus (that will be goofy), hyperfocal point, some average distance of say 10 feet? Lens formulas certainly do affect other lens characteristics. Not totally related actual transmission or exposure of rather different lenses can vary, say a prime to zoom actual exposure might not be the theoretical same at the same F-stop. Here we are again comparing different sorts of lenses. Anyone remember back a few weeks ago the strange demonstration involving the actual magnification of the image of a door knob where different lenses of the same focal length produced different sized images? One might think that is not supposed to happen, but it does. A few UHH members explained it to the rest of us. Seemed to have something to do with theoretical focal length vs effective or actual focal length of a lens. That was part of the explanation (focus breathing).
I am interested in the post you refer to can you either tell the name of it, or give a Link?
I am interested in the post you refer to can you either tell the name of it, or give a Link?
Mar 27, 2017 10:49:37 #
Chefneil wrote:
Indeed, as I was reading through these posts that project came to mind. I'm going to do that and post results. I'm not sure when I'll be able to do so due to work and general Life, but I will...
I for one will be eagerly awaiting your test results. Interesting thread!
Mar 28, 2017 06:05:52 #
James Slick
Loc: Pittsburgh,PA
LensWork wrote:
Yes, given your parameters (same aperture and camera to subject distance, the rest has no effect on DOF), all of the lenses at (true) 90mm will have the same depth of field. What you may find is that the marked 90mm setting on each lens may, or may not, actually be 90mm.
I'm willing to bet this potential inaccuracy goes up with the "spread" of focal length on "zooms". It's something I haven't really thought about.
Mar 28, 2017 07:24:28 #
Chefneil wrote:
I'll bet this question has been asked many times here, but I am going to craft it to get the answer I am looking for.
I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?
I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?
In theory, and in a perfect world - yes, DOF the same -
Mar 28, 2017 08:29:34 #
Chefneil wrote:
I'll bet this question has been asked many times here, but I am going to craft it to get the answer I am looking for.
I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?
I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?
Go to DOF Master, enter your camera (yes a crop sensor vs full frame can affect your DOF) enter your lens and it will show the DOF for that lens.. You can then do each of the others and compare them
http://www.dofmaster.com/dofjs.html
Mar 28, 2017 08:35:55 #
Depth of field should be the same, theoretically, however the look could be quite different depending on the bokeh of the lens. A lens with edgier rendering of out of focus areas, for instance, could make it seem that the DOF is larger. Another related issue is spherical aberration (which affects bokeh). Some lenses do not focus the whole area of the lens at the same point. So some parts of the lens could be in focus for one distance and other parts for another distance. This will absolutely affect the apparent depth of field. I'm attaching such an image. This is done with the front half of an old English projection lens. By removing the rear group, the focal length is made much longer, but it kills the correction of spherical aberration and field flatness that the rear group provided. Out of focus areas, while distorted, also appear sharper than they would normally. This is an extreme example, but your various lenses could give significantly different renderings at the same settings, especially with larger apertures.
Mar 28, 2017 08:38:41 #
To calculate depth of field you need to know the camera being used, focal length of the lens, f-stop, and distance to the subject. With a zoom lens the focal length is constantly being changed. There is no way to calculate depth of field. A prime lens has to be used. If it is for close up objects, use a ruler or tape measure. For extreme dept of field, photoshop can be used. You have to totally understand it to get good results.
Mar 28, 2017 08:50:53 #
catchlight..
Loc: Wisconsin USA- Halden Norway
What Is Depth of Field?
When you focus your camera on a subject, your camera will establish a plane of focus. An imaginary plane is set and the things on that plane are āin focusā, that is your DoF or Depth of Field.
The main element that affects depth of field is distance. More specifically, the distance from the camera to the subject.
As you move closer to your subject, the area of the image that is in focus gets smaller and the opposite is true as you move back.
Depth of focus is a function of aperture.
The short answer is no, it does not change. Each lens will have identical DOF if the distance, aperture and f stop are the same.
When you focus your camera on a subject, your camera will establish a plane of focus. An imaginary plane is set and the things on that plane are āin focusā, that is your DoF or Depth of Field.
The main element that affects depth of field is distance. More specifically, the distance from the camera to the subject.
As you move closer to your subject, the area of the image that is in focus gets smaller and the opposite is true as you move back.
Depth of focus is a function of aperture.
The short answer is no, it does not change. Each lens will have identical DOF if the distance, aperture and f stop are the same.
Mar 28, 2017 09:29:35 #
Gene51 wrote:
But so far, no one has provided the correct and complete answer, or a link to support their opinion.
Or as Dean suggests, test it for yourself. But it will be a little hard to do, since you don't always know what the magnification or focal length is, since lenses often shorten the focal length at close to the minimum focus distance (focus breathing).
Or as Dean suggests, test it for yourself. But it will be a little hard to do, since you don't always know what the magnification or focal length is, since lenses often shorten the focal length at close to the minimum focus distance (focus breathing).
Testing yourself may end up being a bit subjective. However, be sure your distance to subject is the same for all lenses tested. The greater distance will increase the DOF..
Mar 28, 2017 10:10:35 #
gvarner
Loc: Central Oregon Coast
Without getting technical, learn to use hyper focal distance. It will give you peace of mind in the long run. Very helpful in scenic spots but also can be applied effectively in closer work.
Mar 28, 2017 10:34:13 #
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