Wha'ts all this crop sensor DoF Stuff?
May 4, 2024 16:27:23 #
User ID wrote:
Then the f/stop must change.
Nope same f/stop
for example if you calculate the DOF for the 50mm, f/5.6, focus at 5 feet. The DOF is the same for the M43 of 35mm, f/5.6, focus at 5 feet.
Since the crop factor of the M43 is 2 so the formula is 50x1.1414/2
May 4, 2024 16:56:51 #
BebuLamar wrote:
Nope same f/stop
for example if you calculate the DOF for the 50mm, f/5.6, focus at 5 feet. The DOF is the same for the M43 of 35mm, f/5.6, focus at 5 feet.
Since the crop factor of the M43 is 2 so the formula is 50x1.1414/2
for example if you calculate the DOF for the 50mm, f/5.6, focus at 5 feet. The DOF is the same for the M43 of 35mm, f/5.6, focus at 5 feet.
Since the crop factor of the M43 is 2 so the formula is 50x1.1414/2
It's pretty close but the crop factor and the CoC ratio are not exactly 2x and the M43 has a different aspect ratio.
Because of the difference in aspect ratio, the field of view has a 2x factor horizontally but 1.78 vertically.
Here is the list from the spreadsheet:
May 4, 2024 17:03:59 #
selmslie wrote:
It's pretty close but the crop factor and the CoC ratio are not exactly 2x and the M43 has a different aspect ratio.
Because of the difference in aspect ratio, the field of view has a 2x factor horizontally but 1.78 vertically.
Here is the list from the spreadsheet:
Because of the difference in aspect ratio, the field of view has a 2x factor horizontally but 1.78 vertically.
Here is the list from the spreadsheet:
The aspect ratio isn't the same that is why the diagonal should be used rather than horizontal or vertical. The crop factor for M43 is very close to 2. The CoC should be proportional to the diagonal of the format.
The formula as I gave works and answers the OP question. That's all.
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May 4, 2024 17:04:19 #
User ID wrote:
Then the f/stop must change.
It doesn't.
May 4, 2024 17:06:37 #
selmslie wrote:
It doesn't.
No it doesn't but keep in mind that the 35mm on M43 gives narrower angle of view than a 50mm on FF. If you use the 25mm lens to get the same angle of view then you have to open up about 1 stop to get the same DOF. Again, my post is to answer the OP question whether or not it's useful I don't want to discuss.
May 4, 2024 17:11:32 #
BebuLamar wrote:
No it doesn't but keep in mind that the 35mm on M43 gives narrower angle of view than a 50mm on FF. If you use the 25mm lens to get the same angle of view then you have to open up about 1 stop to get the same DOF. Again, my post is to answer the OP question whether or not it's useful I don't want to discuss.
As mentioned, the f/stop changed. Applying your formula to non equivalent FLs is just a red herring. Pure UHH.
May 4, 2024 17:14:29 #
BebuLamar wrote:
No it doesn't but keep in mind that the 35mm on M43 gives narrower angle of view than a 50mm on FF. If you use the 25mm lens to get the same angle of view then you have to open up about 1 stop to get the same DOF. Again, my post is to answer the OP question whether or not it's useful I don't want to discuss.
You are correct about the field of view. But if you are searching for equivalence, that's a whole different rabbit hole because of the aspect ratio.
I actually prefer an aspect ratio closer to 4:3 or 5:4 because it's easier to frame. I can actually get a raw file from the Z7 that is 5:4 or 1:1 instead of 3:2.
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May 4, 2024 17:22:10 #
User ID wrote:
As mentioned, the f/stop changed. Applying your formula to non equivalent FLs is just a red herring. Pure UHH.
The f/stop doesn't change. The 50mm f/5.6 focus at 5 feet on FF gives the same DOF for the M43 with 35mm, f/5.6 focus at 5 feet.
The Field of View are different.
But the the formula answer the OP question.
May 4, 2024 18:32:58 #
BebuLamar wrote:
The f/stop doesn't change. The 50mm f/5.6 focus at 5 feet on FF gives the same DOF for the M43 with 35mm, f/5.6 focus at 5 feet.
The Field of View are different.
But the the formula answer the OP question.
The Field of View are different.
But the the formula answer the OP question.
Just read op again. He does keep comparing 35mm on m4/3 to 50mm on FF. Thaz NOT equivalent, but it *IS* the op question. On that basis I do see what you mean.
May 4, 2024 18:41:32 #
User ID wrote:
Just read op again. He does keep comparing 35mm on m4/3 to 50mm on FF. Thaz NOT equivalent, but it *IS* the op question. On that basis I do see what you mean.
Yes he found that the 35mm lens on M43 has the same DOF as the 50mm on FF at the same aperture. He asked what kind of mathematical relationship are they so I gave him the formula. That is focal length on FF multiplied by the square root of the crop factor and divided by the crop factor gives you the focal length that give the same DOF on a crop sensor. Not the same field of view but his question doesn't say anything about the field of view.
I don' say it's useful for anything or not. Just the direct answer to the question asked.
May 4, 2024 19:21:32 #
User ID wrote:
Dont worry that "maybe its only close".
"Only close" is what DoF is all about.
Its about whats good enuf on either side of perfect. Despite formulae and CoC standards, "good enuf" is a subjective case-by-case call, and therefor a variable.
"Only close" is what DoF is all about.
Its about whats good enuf on either side of perfect. Despite formulae and CoC standards, "good enuf" is a subjective case-by-case call, and therefor a variable.
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