Depth of field
Jul 25, 2022 13:54:09 #
Is the depth of field the same for a 35mm prime lens as a 17-70mm zoom set at 35mm??? Thanks in advance…
Jul 25, 2022 13:57:36 #
Ysarex
Loc: St. Louis
Gdelvecc wrote:
Is the depth of field the same for a 35mm prime lens as a 17-70mm zoom set at 35mm??? Thanks in advance…
Yes, assuming all else equal like same aperture. The prime lens will typically have an aperture that opens wider.
Jul 25, 2022 14:15:49 #
Gdelvecc wrote:
Is the depth of field the same for a 35mm prime lens as a 17-70mm zoom set at 35mm??? Thanks in advance…
Yes.
A prime lens is just a zoom thaz been locked at one focal length. Acoarst some mechanical parts are omitted by design.
Jul 25, 2022 15:20:52 #
Gdelvecc wrote:
Is the depth of field the same for a 35mm prime lens as a 17-70mm zoom set at 35mm??? Thanks in advance…
Actually NO.
Each lens is build for a purpose. While the DOF does not change across a lens of the same length and model from the same manufacturer, this becomes false as soon as you change it, even if only the model.
So, the same between a zoom and fixed lens? Nope. The differences may not be obvious, but they exist.
Reason:
The glass is different.
The glass groupings are different.
The motion between the groups is different.
Try shooting a chart at the same distance, on a tripod. You will see that the distortion has changed and so did the perspective.
Jul 25, 2022 15:47:35 #
Jul 25, 2022 16:32:21 #
User ID wrote:
Yes.
A prime lens is just a zoom thaz been locked at one focal length. Acoarst some mechanical parts are omitted by design.
A prime lens is just a zoom thaz been locked at one focal length. Acoarst some mechanical parts are omitted by design.
Seriously?!
Jul 25, 2022 17:19:23 #
Rongnongno wrote:
Actually NO. br br Each lens is build for a purpo... (show quote)
ROTFLMFAO
Imaginary differences defined by geeks. Best approach is to unsee it.
Jul 25, 2022 17:20:06 #
Jul 25, 2022 17:36:46 #
User ID wrote:
ROTFLMFAO
Imaginary differences defined by geeks. Best approach is to unsee it.
Imaginary differences defined by geeks. Best approach is to unsee it.
Of course they are different. How do you set the zoom at exactly 35mm for example. Aperture and focal length have tolerance and the lenses are not exactly as specs. The amount of focus breathing is also different and thus the focal lengths are different although they are supposed to be the same.
Jul 25, 2022 18:52:42 #
BebuLamar wrote:
Of course they are different. How do you set the zoom at exactly 35mm for example. Aperture and focal length have tolerance and the lenses are not exactly as specs. The amount of focus breathing is also different and thus the focal lengths are different although they are supposed to be the same.
So, clearly nothing significant. Not news.
Jul 25, 2022 18:57:01 #
Yes, assuming the same aperture, distance to subject and acceptable CoC (related to sensor size). And regarding CoC/sensor size, before someone objects:
Sensor size affects DOF in counterintuitive ways. Because the circle of confusion is directly tied to the sensor size, decreasing the size of the sensor while holding focal length and aperture constant will decrease the depth of field (by the crop factor). The resulting image however will have a different field of view. If the focal length is altered to maintain the field of view, the change in focal length will counter the decrease of DOF from the smaller sensor and increase the depth of field (also by the crop factor). Per Wiki: https://en.m.wikipedia.org/wiki/Depth_of_field
Sensor size affects DOF in counterintuitive ways. Because the circle of confusion is directly tied to the sensor size, decreasing the size of the sensor while holding focal length and aperture constant will decrease the depth of field (by the crop factor). The resulting image however will have a different field of view. If the focal length is altered to maintain the field of view, the change in focal length will counter the decrease of DOF from the smaller sensor and increase the depth of field (also by the crop factor). Per Wiki: https://en.m.wikipedia.org/wiki/Depth_of_field
Jul 26, 2022 07:56:00 #
Rongnongno wrote:
Actually NO.
...
So, the same between a zoom and fixed lens? Nope. The differences may not be obvious, but they exist.
Reason:
The glass is different.
The glass groupings are different.
The motion between the groups is different.
Try shooting a chart at the same distance, on a tripod. You will see that the distortion has changed and so did the perspective.
...
So, the same between a zoom and fixed lens? Nope. The differences may not be obvious, but they exist.
Reason:
The glass is different.
The glass groupings are different.
The motion between the groups is different.
Try shooting a chart at the same distance, on a tripod. You will see that the distortion has changed and so did the perspective.
Distortion has nothing to do with DOF. DOF does not change.
Even with different focal lengths from the same position the perspective will not change, only the field of view.
Jul 26, 2022 10:03:32 #
Rongnongno wrote:
Actually NO…….
For the untrained eye, the differences are rarely noticed. There are significant differences in the elements. This is an exacting science where the density of the material, it’s thickness and other physical features are ground to a specific design. That is why lenses get ridiculously expensive. The research garnered for lenses is very time consuming. Slight changes in one aspect like the barrel width will affect the thickness of the element and the aperture settings. Small Lenses are often painted black. For this reason, lenses are painted white to reflect sunlight and prevent distortion of the elements within. This will change the extension and contraction of the elements.
The depth of field is an extremely dynamic feature but only trained eyes will notice these differences. After forty or so years of photography, I still have great difficulty in detecting these features.
Jul 26, 2022 10:14:45 #
My favorite pastime is tabletop micro/macro focus stacking photography where I use a variety of optics and means of extensions. An important part of the process is to determine what the resulting depth of field will be so that I can set the distance of camera travel required for each shot taken. To do this, I use the following method of calculation:
DOF = (0.0022*N*N*(m+1)*(m+1))/(m*m) , where N is the F-number and m is magnification. The result is the depth of field measured in millimeters.
DOF = (0.0022*N*N*(m+1)*(m+1))/(m*m) , where N is the F-number and m is magnification. The result is the depth of field measured in millimeters.
Jul 26, 2022 11:56:09 #
mwsilvers
Loc: Central New Jersey
Gdelvecc wrote:
Is the depth of field the same for a 35mm prime lens as a 17-70mm zoom set at 35mm??? Thanks in advance…
Since depth of field is a function of the aperture the lens is set to, your comparison is too simplistic. It not only leaves relative f-stops out of the equation, but lens design and an understanding of optics has to be considered.
In a perfect world with perfect lenses, theoretically the DOF for any two lenses at the same focal length and the same aperture shooting the same subject at the same distance in the same light should be similar. But, the world isn't perfect.
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