The lenses we use

[ChrisR]

Both of your images deep in diffraction field and too small and resized by differnt scale to talk about comparision of DoF

. No they are not. This is a point you appear to be missing.
Look at objective manufacturers' specifications. They can quote a DOF for their lens, because it relates to the aperture/NA/resolution of the lens.

If you want more DOF, use a sensor with huge pixels. But that is throwing away the resolution of the lens.
You can obviously, of course, make the DOF, as limited by you, whatever you want.
Then you are using well accepted geometry calculations, which, in the end, say "everything is proportional".

But, so what? It's only because of a limitation you applied.

[Justwalking]

. No they are not. This is a point you appear to be missing.

I'm not missing with it.

diffraction is a greater issue in close-up photography, and the tradeoff between DOF and overall sharpness can become quite noticeable (Gibson 1975, 53; Lefkowitz 1979, 84).

If you want more DOF, use a sensor with huge pixels.

I did not understand this kind of joke, sorry.
With huge pixels you need huge magnification for the same resolution on the same FoV.
And calculation is also have said that Dof will be less.

http://resourcemagonline.com/2014/02/ef ... eld/36402/

[ray_parkhurst]

I'm not missing with it.

Indeed you are missing some important points, and have been making some calculation and conceptual errors.

You found a nice lens that works well with a small sensor. At low macro magnifications it produces a large depth of field due to combination of low mag and relatively small aperture. Downsizing the images for web publishing results in very nice, sharp, wide DOF images. You are attributing this to some magical combination that defies the laws of physics, and unfortunately you are supported by a range of articles written by non-technical folks who don't understand the underlying principles they are trying to explain.

Rik and others on this forum have provided solid technical explanations for what you are seeing, but unfortunately again you keep going back to the non-technical folks to support what you believe. Based on what I've seen in your responses, no matter what anyone says to try to explain your results in context of the physical parameters, you are not able to accept their inputs, and each time give some convoluted explanation and further "references".

It's nice that your lens and camera produce good images, and the depth of field without stacking is indeed enviable. But it is not magic, and it is not the only way to achieve these results.

[Justwalking]

Rik and others on this forum have provided solid technical explanations for what you are seeing, but unfortunately again you keep going back to the non-technical folks to support what you believe.

Downsizing to screen works also with FF. We have formula for standart
comparision on print from standart point of view.
Is the formula with magnification non-technical folks?
If you believe that fornula don't work it is not my probs.

It's nice that your lens and camera produce good images, and the depth of field without stacking is indeed enviable. But it is not magic, and it is not the only way to achieve these results.

Off course it is not magic, but math.
Exactly. You can stack several images with less DoF on each due to needed more magnification to obtain better result.

[Lou Jost]

Justwalking, perhaps you have seen the depth-of-field tables that Rik has made for Zerene:
http://zerenesystems.com/cms/stacker/do ... romicrodof
We all use these all the time. They work. They've been tested by us thousands of times. Your suggestion that Rik doesn't know how depth of field works is simply wrong.

[ray_parkhurst]

Is the formula with magnification non-technical folks?
If you believe that fornula don't work it is not my probs.

For sure the DOF formula works, but you can use it to make all sorts of wrong conclusions, as several of the articles do.

You can stack several images with less DoF on each due to needed more magnification to obtain better result.

Or, you can shoot with a larger sensor, at higher magnification, and smaller aperture, and get the same result without stacking.

[Justwalking]

For sure the DOF formula works, but you can use it to make all sorts of wrong conclusions, as several of the articles do.

Which conclusion is wrong about magnification?

Or, you can shoot with a larger sensor, at higher magnification, and smaller aperture, and get the same result without stacking.

We don't talk here about possibility for the larger sensor to achieve same DoF.
We are talking about same F-working for both systems.
What if i start 2X Mag at f5.6 Eff - where would be Feff on FF for same FoV? Probably in diffraction field territory. F eff rise much less than M^2.

[ray_parkhurst]

Which conclusion is wrong about magnification?

I don't know what you are asking. They are wrong about DOF. How could they be wrong about magnification? Or was that just a typo?

We don't talk here about possibility for the larger sensor to achieve same DoF.

I think this is one of your misunderstandings. Rik showed that equivalent images could be shot with FF and small sensor. The two images had the same DOF. DOF is critical to the discussion.

We are talking about same F-working for both systems.
What if i start 2X Mag at f5.6 Eff - where would be Feff on FF for same FoV? Probably in diffraction field territory. F eff rise much less than M^2.

No, not same effective aperture. That is the mistake you are making. You are correct that the large sensor is much farther into diffraction. In Rik's earlier example, the small sensor is at f10, and large sensor at f55. But when they are viewed at the same output image size, they look the same. The diffraction blur is reduced due to the downsizing of the larger image.

A key concept here is that the relevant CoC relates to the output image, not the source image. This means the source image CoC is larger for the larger sensor, compensating the smaller effective aperture.

[rjlittlefield]

We are talking about same F-working for both systems.

No problem there. If you want to have same F-working on large and small sensors, with same FOV, then for sure DOF will be less on the large sensor. But at the same time, the large sensor will resolve more detail. This is because you have swapped the lens for one with larger NA. That case is the third line in the diagram I posted, HERE.

Nobody is debating whether the formulas are correct. The formulas are fine. I know them forwards and backwards and I use them often. All the formulas referenced by Justwalking are correct.

The debate about the formulas is really about what numbers to plug into them.

The numbers that Justwalking chooses, correspond to changing the lens system so that the larger sensor does have less DOF. The same change means that the system will also resolve finer detail on subject. I don't know if Justwalking doesn't understand that, or if he's trolling us.

What the formulas show, when correct numbers are plugged in, is that at same FOV and same NA, all size sensors produce images that have the same DOF and same resolution on subject. Experiment shows the same thing.

To repeat myself, the formulas are correct.

Likewise the articles are correct. The question there is, what are the articles correct about? That is, what do they hold constant, and how do other things change besides the ones that they mention?

It is completely true that if you shoot the same FOV at the same F-number setting of the lens, then a larger sensor will have less DOF. At the same time, the larger sensor will capture finer detail on subject. Both of those happen for the same reason: at same F-number, the larger lens will have a larger aperture, resulting in larger NA on the subject side. The articles mention the loss of DOF, but they do not mention the finer detail. If, instead, they just stopped down the larger lens so as to maintain the same diameter hole in both lenses, then both cameras would capture the same DOF and the same level of diffraction-limited detail. But this is complicated to explain to a general audience, so almost no articles mention it.

There is one very useful article that has not been referenced yet: Richard F. Lyon's "Depth of Field Outside the Box".

Quoting from page 8 of 39:

4. If you reduce the focal length as above, but fix the aperture diameter d by also scaling to a lower f-number by the same format-size factor, then d/e and S remain the same, giving you the same DOF. From the “outside-the-box” viewpoint, your camera is no different, as it has the same aperture diameter, same position, and same field of view. Its format doesn’t matter. You also get equal amounts of blur due to diffraction in this case, but likely worse aberrations in the smaller camera since it is working at a lower f-number.

Notice that changing to a smaller format can make your depth of field higher, lower, or unchanged, depending on what you keep fixed.

This is, of course, exactly the same thing that I've been saying. But it's not consistent with what Justwalking wants to believe, so I assume that he will find some way to reject it.

--Rik

[Justwalking]

No, not same effective aperture. That is the mistake you are making. You are correct that the large sensor is much farther into diffraction. In Rik's earlier example, the small sensor is at f10, and large sensor at f55. But when they are viewed at the same output image size, they look the same. The diffraction blur is reduced due to the downsizing of the larger image.

Both picture are strong blurred even in best focus point and overall low sharpness can't give us the chance to compare their DoF.

[rjlittlefield]

Both picture are strong blurred even in best focus point and overall low sharpness can't give us the chance to compare their DoF.

So, now you're telling us you can't see that the upper antenna is even more blurred than the bottom one? And that it's equally blurred in both images?

--Rik

[Justwalking]

We are talking about same F-working for both systems.

No problem there. If you want to have same F-working on large and small sensors, with same FOV, then for sure DOF will be less on the large sensor. But at the same time, the large sensor will resolve more detail. This is because you have swapped the lens for one with larger NA.

Rik, where is your NA in Formula of DoF? We don't talk here about better resolving the subject. We talk about Dof of the "same" picture.
You can't resolve more than 16MP with any NA in our example.

The numbers that Justwalking chooses, correspond to changing the lens system so that the larger sensor does have less DOF. The same change means that the system will also resolve finer detail on subject. I don't know if Justwalking doesn't understand that, or if he's trolling us.

No. The math trolling you.
When the "same picture" is taken in two different format sizes from the same distance at the same f-number with lenses that give the same angle of view, and the final images (e.g., in prints, or on a projection screen or electronic display) are the same size, DOF is, to a first approximation, inversely proportional to format size (Stroebel 1976, 139).

What the formulas show, when correct numbers are plugged in, is that at same FOV and same NA, all size sensors produce images that have the same DOF and same resolution on subject. Experiment shows the same thing.

Again: there are nothing about NA and resolving power in formula of DoF.

It is completely true that if you shoot the same FOV at the same F-number setting of the lens, then a larger sensor will have less DOF. At the same time, the larger sensor will capture finer detail on subject. Both of those happen for the same reason: at same F-number, the larger lens will have a larger aperture, resulting in larger NA on the subject side. The articles mention the loss of DOF, but they do not mention the finer detail. If, instead, they just stopped down the larger lens so as to maintain the same diameter hole in both lenses, then both cameras would capture the same DOF and the same level of diffraction-limited detail. But this is complicated to explain to a general audience, so almost no articles mention it.

To avoid be diffraction limited byaperture i told that you can compare at F/4 eff. Formula mention less of Dof by magnification not anytying else.

From the “outside-the-box” viewpoint, your camera is no different, as it has the same aperture diameter, same position, and same field of view. Its format doesn’t matter.
Notice that changing to a smaller format can make your depth of field higher, lower, or unchanged, depending on what you keep fixed.
This is, of course, exactly the same thing that I've been saying. But it's not consistent with what Justwalking wants to believe, so I assume that he will find some way to reject it.
--Rik

Yes, i I give you alreary article about different combination of fixed already.
But we interesting only in one case: to take equivalent field of view
In short, it is approximately true that adjusting both the focal length and aperture by the ratio of the format sizes (the crop factor) will give you the same picture.


But this breaks down if the subject is within the macro range. In this case, magnification (and therefore actual sensor size) becomes crucial to the DoF equation, messing up the equivalence.

[Justwalking]

Both picture are strong blurred even in best focus point and overall low sharpness can't give us the chance to compare their DoF.

So, now you're telling us you can't see that the upper antenna is even more blurred than the bottom one? And that it's equally blurred in both images?

--Rik

Of course they looks less blurred due to different FoV that mean that is less
magnification from the same distance view. if you resize them furter to 20X20 they probably become sharp as razor blade. ))

[rjlittlefield]

Rik, where is your NA in Formula of DoF?

I believe you wrote this?

I hope ppl working with macro well known this formula for Dof (simplified but pretty accurate)
DOF ~ 2F'c/M^2, where F' - working number, c - circle of confusion, M - magnfication.

I guess you don't know that F' = M/(2*NA). It is a fundamental property of lens systems, due to Lagrange invariant.

Then just do the algebra:
2F'c/M^2 = c/(M*NA)

--Rik

[Justwalking]

Rik, where is your NA in Formula of DoF?

I believe you wrote this?

I hope ppl working with macro well known this formula for Dof (simplified but pretty accurate)
DOF ~ 2F'c/M^2, where F' - working number, c - circle of confusion, M - magnfication.

I guess you don't know that F' = M/(2*NA). It is a fundamental property of lens systems, due to Lagrange invariant.

Then just do the algebra:
2F'c/M^2 = c/(M*NA)

--Rik

Well, you have still M as inverse proportional to the Dof. So instead previous F' now you need to change the lens NA to the sensor size.
If your think that it is easy to take NA greater at 5.5X for the same FoV
let it be.