Estimating depth of field

Started Feb 21, 2013 | Discussions
Anders W
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Re: Estimating depth of field
In reply to richarddd, Feb 26, 2013

richarddd wrote:

Are there any good illustrations showing DOF v. diffraction? For example, a series of landscape shots showing that apparent DOF increases with f-stop, but that at some point diffraction takes over? Or are there too many variables for such a series of photos to be useful?

No, I haven't seen an illustration of both things simultaneously, only of one or the other. But I see no problems of accomplishing one where you could see the trade-off with your own eyes.

What are the main variable in the trade-off between diffraction and DOF?

Only two: Assuming the lens has already been stopped down to its peak resolution at the outset, what will happen as you stop down further is that the DoF will become deeper and deeper but the resolution of things within the DoF increasingly poor. In essence, you buy increased resolution in some places at the expense of less resolution in others. However, if you could stop down far enough, you would eventually reach a point where sharpness would decline across the entire frame so that there would be no increase left to buy anywhere.

Any thoughts on this calculator, which purports to show, among other measures, DOF v. diffraction. http://www.stegmann.dk/mikkel/barnack/

Haven't seen that before but looks quite interesting so thanks for drawing my attention to it. Looks like it might be quite useful, not for use in the field, but for thinking and discussing about what we might want to do in the field, as we do at the moment.

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Detail Man
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Re: Estimating depth of field
In reply to richarddd, Feb 26, 2013

richarddd wrote:

Any thoughts on this calculator, which purports to show, among other measures, DOF v. diffraction. http://www.stegmann.dk/mikkel/barnack/

It's a nice little application that seems to run fine on my WinXP Pro SP3 OS. Creating custom camera entries in the database is relatively easy to do. Good resolution of chosen COC diameter.

From the program's Help information:

Diffraction spot diameter
The diffraction spot diameter measures how much a light beam is Fraunhofer diffracted by a circular aperture. Barnack calculates the diameter of the Airy pattern for light at the selected wavelength where it contains approximately 84 percent of the total light energy. Diffraction constitutes the upper limit for optical performance. Hence, the circle of confusion should not be smaller than the diffraction spot.

Reports the circular aperture diffraction diameter (so it can be compared with the COC diameter).

Wavelength
The wavelength of the light used in the diffraction spot diameter calculation and all MTF estimates.

The Difraction-limited MTF vs. Resolution graph reflects the effects of "pure diffraction" only.

The graph does not appear to calculate the composite effects of circular aperture diffraction (when that diameter is larger than the diameter of the COC which enters into the calculation of DOF) combined with "pure diffraction" on the MTF.

The X-axis coordinates (in spatial-frequency units of line-pars per miliMeter) varies as a function of the selected Wavelength and F-Number ("Aperture").

The precise meaning of the (green and gray colored) vertical display-lines are unclear to me. The X-axis coordinates of the gray-colored line appears to always be approximately equal to twice (2x)  the value of the green-colored line.

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Detail Man
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Clarification: Estimating depth of field
In reply to Detail Man, Feb 26, 2013

Detail Man wrote:

The Difraction-limited MTF vs. Resolution graph reflects the effects of "pure diffraction" only.

The graph does not appear to calculate the composite effects of circular aperture diffraction (when that diameter is larger than the diameter of the COC which enters into the calculation of DOF) combined with "pure diffraction" on the MTF.

The X-axis coordinates (in spatial-frequency units of line-pars per miliMeter) varies as a function of the selected Wavelength and F-Number ("Aperture").

The precise meaning of the (green and gray colored) vertical display-lines are unclear to me. The X-axis coordinates of the gray-colored line appears to always be approximately equal to twice (2x) the value of the green-colored line.

The green and gray colored vertical lines in the Difraction-limited MTF vs. Resolution graphical display appear at fixed spatial-frequency values (in units of line-pars per milliMeter), regardless of the specified Wavelength and F-Number values.

The green colored vertical line corresponds to the vertical resolution (in units of line-pars per milliMeter) of an individual photo-site on the analyzed camera's image-sensor.

The gray colored vertical line corresponds to the vertical resolution (in units of line-pars per milliMeter) of a 2x2 array of photo-sites on the analyzed camera's image-sensor.

Those statistics are displayed for the camera being analyzed by clicking on Camera - Details.

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Chez Wimpy
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Re: look at that!
In reply to Anders W, Feb 26, 2013

Anders W wrote:

Things at the edges tend to be closer to the camera (or rather to a plane in front of the camera) than those at the center so that the field curvature in practice helps extend the DoF.

It is interesting that the 24TSEII has pretty pronounced field curvature as well.  This is a problem in landscapes with deep DOF (the side of the image near the horizon are usually soft unless you are stopped down a bit), the workaround is to focus with LV on the edges of the shifted image circle and let the center infinity suffer a bit for better consistency.  There is also a fair bit of image distortion in the complete image circle - but it doesn't much matter with TS landscapes (architecture is different of course) because lens rises and falls the horizon near the straight-line optical center.

Well the wind hits the "prairie" around Uppsala too from time to time, but we do have our quiet moments where focus-stacking a meadow full of spring blossoms wouldn't be much of a problem I would think (still have to try). And imagine the time, soon to come of course , when the camera will bracket focus in burst-mode just as conveniently as it already does when it comes to exposure.

One of the other problems with focus stacking with most DSLR lenses is focus breathing.  These are not designed for cinema use, and digital stacking is clearly not in the basic parameters.  With the 90TSE and my 70-200/2.8IS in my few (unsatisfactory) attempts, the planes don't match up.  There is perhaps as much as a 10% shift in image size (or more precisely focal length change) as you go from close to infinity.  I don't shoot macro so I don't know if this is a problem there, or something that can be worked around with automated software (I do my masking by hand).

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richarddd
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Re: Estimating depth of field
In reply to Anders W, Feb 26, 2013

Anders W wrote:

richarddd wrote:

Are there any good illustrations showing DOF v. diffraction? For example, a series of landscape shots showing that apparent DOF increases with f-stop, but that at some point diffraction takes over? Or are there too many variables for such a series of photos to be useful?

No, I haven't seen an illustration of both things simultaneously, only of one or the other. But I see no problems of accomplishing one where you could see the trade-off with your own eyes.

Do you have any suggestions for designing and executing such a test?

What are the main variable in the trade-off between diffraction and DOF?

Only two: Assuming the lens has already been stopped down to its peak resolution at the outset, what will happen as you stop down further is that the DoF will become deeper and deeper but the resolution of things within the DoF increasingly poor. In essence, you buy increased resolution in some places at the expense of less resolution in others. However, if you could stop down far enough, you would eventually reach a point where sharpness would decline across the entire frame so that there would be no increase left to buy anywhere.

"what a small aperture giveth, diffraction taketh away"

Does lens design matter or is aperture the only relevant variable for a given sensor size?

Any thoughts on this calculator, which purports to show, among other measures, DOF v. diffraction. http://www.stegmann.dk/mikkel/barnack/

Haven't seen that before but looks quite interesting so thanks for drawing my attention to it. Looks like it might be quite useful, not for use in the field, but for thinking and discussing about what we might want to do in the field, as we do at the moment.

In this context, would the key numbers be the circle of confusion compared to the diffraction spot diameter, with the idea that once the diffraction spot passes the CoC, there is no further DoF increase?

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Detail Man
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Re: Clarification: Estimating depth of field
In reply to Detail Man, Feb 26, 2013

Detail Man wrote:

Detail Man wrote:

The Difraction-limited MTF vs. Resolution graph reflects the effects of "pure diffraction" only.

The graph does not appear to calculate the composite effects of circular aperture diffraction (when that diameter is larger than the diameter of the COC which enters into the calculation of DOF) combined with "pure diffraction" on the MTF.

The X-axis coordinates (in spatial-frequency units of line-pars per miliMeter) varies as a function of the selected Wavelength and F-Number ("Aperture").

On the Difraction-limited MTF vs. Resolution display-graph, the limitations on the percentage MTF caused by "pure diffraction" increases (and the spatial-frequency of "extinction" decreases) in linear proportion to the individual selected values of Wavelength and F-Number ("Aperture").

The precise meaning of the (green and gray colored) vertical display-lines are unclear to me. The X-axis coordinates of the gray-colored line appears to always be approximately equal to twice (2x) the value of the green-colored line.

The green and gray colored vertical lines in the Difraction-limited MTF vs. Resolution graphical display appear at fixed spatial-frequency values (in units of line-pars per milliMeter), regardless of the specified Wavelength and F-Number values.

The green colored vertical line corresponds to the vertical resolution (in units of line-pars per milliMeter) of an individual photo-site on the analyzed camera's image-sensor.

The gray colored vertical line corresponds to the vertical resolution (in units of line-pars per milliMeter) of a 2x2 array of photo-sites on the analyzed camera's image-sensor.

On the Difraction-limited MTF vs. Resolution display-graph, when the mouse-pointer is placed on top of the green or the gray vertical lines in the display, the limitations in the percentage MTF resulting from the corresponding (individual photo-site, or 2x2 array of photo-sites) vertical resolution limits are indicated by the horizontal dotted-line that intersects the Y-axis of the display.

Those statistics are displayed for the camera being analyzed by clicking on Camera - Details.

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richarddd
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Re: Estimating depth of field
In reply to Detail Man, Feb 26, 2013

Detail Man wrote:

richarddd wrote:

Any thoughts on this calculator, which purports to show, among other measures, DOF v. diffraction. http://www.stegmann.dk/mikkel/barnack/

It's a nice little application that seems to run fine on my WinXP Pro SP3 OS. Creating custom camera entries in the database is relatively easy to do. Good resolution of chosen COC diameter.

From the program's Help information:

Diffraction spot diameter
The diffraction spot diameter measures how much a light beam is Fraunhofer diffracted by a circular aperture. Barnack calculates the diameter of the Airy pattern for light at the selected wavelength where it contains approximately 84 percent of the total light energy. Diffraction constitutes the upper limit for optical performance. Hence, the circle of confusion should not be smaller than the diffraction spot.

Reports the circular aperture diffraction diameter (so it can be compared with the COC diameter).

Would there be any DOF benefit to decreasing aperture beyond the point where the calculated diffraction spot diameter equals the COC?

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Detail Man
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Re: For Richarddd
In reply to Detail Man, Feb 26, 2013

Detail Man wrote:

Detail Man wrote:

Detail Man wrote:

The Diffraction-limited MTF vs. Resolution graph reflects the effects of "pure diffraction" only.

The graph does not appear to calculate the composite effects of circular aperture diffraction (when that diameter is larger than the diameter of the COC which enters into the calculation of DOF) combined with "pure diffraction" on the MTF.

The X-axis coordinates (in spatial-frequency units of line-pars per miliMeter) varies as a function of the selected Wavelength and F-Number ("Aperture").

On the Diffraction-limited MTF vs. Resolution display-graph, the limitations on the percentage MTF caused by "pure diffraction" increases (and the spatial-frequency of "extinction" decreases) in linear proportion to the individual selected values of Wavelength and F-Number ("Aperture").

The precise meaning of the (green and gray colored) vertical display-lines are unclear to me. The X-axis coordinates of the gray-colored line appears to always be approximately equal to twice (2x) the value of the green-colored line.

The green and gray colored vertical lines in the Diffraction-limited MTF vs. Resolution graphical display appear at fixed spatial-frequency values (in units of line-pars per milliMeter), regardless of the specified Wavelength and F-Number values.

The green colored vertical line corresponds to the vertical resolution (in units of line-pars per milliMeter) of an individual photo-site on the analyzed camera's image-sensor.

The gray colored vertical line corresponds to the vertical resolution (in units of line-pars per milliMeter) of a 2x2 array of photo-sites on the analyzed camera's image-sensor.

On the Diffraction-limited MTF vs. Resolution display-graph, when the mouse-pointer is placed on top of the green or the gray vertical lines in the display, the limitations in the percentage MTF resulting from the corresponding (individual photo-site, or 2x2 array of photo-sites) vertical resolution limits are indicated by the horizontal dotted-line that intersects the Y-axis of the display.

Those statistics are displayed for the camera being analyzed by clicking on Camera - Details.

Richarddd wrote:

Would there be any DOF benefit to decreasing aperture beyond the point where the calculated diffraction spot diameter equals the COC?

Rather than thinking of the effects of diffraction in terms of a calculated DOF value, think of it in terms of the actual spatial-frequency resolution that results as a combination of the effects.

It may seem a bit counter-intuitive, but when the diameter of the COC increases, the DOF increases, but the spatial-frequency resolution always decreases as a result (in any situation, including ones where the "diffraction spot diameter" is smaller than the COC).

Thus, when the "diffraction spot diameter" exceeds the COC diameter, the net spatial-frequency resolution that results futher decreases.

Using the Barnack program, change the Wavelength (leaving the selected value of the F-Number fixed), and note that the calculated DOF (and Hyperfocal Distance) do not change - even when the "diffraction spot diameter" exceeds the COC diameter (however the COC is specified). They implement the program this way so as not to confuse the users. When the "diffraction spot diameter" exceeds the COC diameter, the diffraction dominates over the COC.

However, select and view the Diffraction-limited MTF vs. Resolution display-graph, and you can see and measure how much the total net spatial-frequency resolution decreases as the "diffraction spot diameter" exceeds the COC diameter using the following procedure:

On the Diffraction-limited MTF vs. Resolution display-graph, move the mouse-pointer horizontally across the display, and the limitations in the percentage MTF resulting from the selected value of F-Number (and also any increases in the value of the selected Wavelength) at any particular spatial-frequency (in line-pairs per milliMeter) is indicated by the horizontal dotted-line that intersects the Y-axis of the display. The X-axis and Y-axis coordinates (of the "crosshairs") are displayed in the upper-right of the display.

The percentage value of the MTF (Modulation Transfer Function) curve corresponds directly with the spatial-frequency resolution. The lower the percentage MTF, the lower the spatial-frequency resolution (relative to the 100% value, which is located at a value of Zero lp/mm).

.

The Diffraction-limited MTF vs. Resolution display-graph shows you the correspondence between the composite effects of the DOF (in what is actually the COC "trumped" when the "diffraction spot diameter" exceeds the COC diameter) and the additional effects of the "pure diffraction" that you have been asking about being able to assess in your previous posted inquiry. It shows you that information by relating the spatial-frequency resolution as a percentage MTF value.

It shows you the bottom-line of how the spatial-frequency resolution is affected (in line-pairs per milliMeter, lp/mm). To covert that to line-pairs per image-height (lph), multiply the result by the vertical height (in units of milliMeters) of the active area of the image sensor.

DM...

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Detail Man
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Re: Estimating depth of field
In reply to richarddd, Feb 26, 2013

richarddd wrote:

Anders W wrote:

richarddd wrote:

Are there any good illustrations showing DOF v. diffraction? For example, a series of landscape shots showing that apparent DOF increases with f-stop, but that at some point diffraction takes over? Or are there too many variables for such a series of photos to be useful?

No, I haven't seen an illustration of both things simultaneously, only of one or the other. But I see no problems of accomplishing one where you could see the trade-off with your own eyes.

Do you have any suggestions for designing and executing such a test?

Every lens is different - but they all tend to have the highest value of MTF in the center, decreasing as the edges/corners are approached. The effects of diffraction will tend to degrade the MTF equally across the lens. Because the MTF is lower in the first place in the edges/corners, the results will become undesirably blurred sooner around the edges/corners.

What are the main variable in the trade-off between diffraction and DOF?

Only two: Assuming the lens has already been stopped down to its peak resolution at the outset, what will happen as you stop down further is that the DoF will become deeper and deeper but the resolution of things within the DoF increasingly poor. In essence, you buy increased resolution in some places at the expense of less resolution in others. However, if you could stop down far enough, you would eventually reach a point where sharpness would decline across the entire frame so that there would be no increase left to buy anywhere.

"what a small aperture giveth, diffraction taketh away"

Does lens design matter or is aperture the only relevant variable for a given sensor size?

Every lens is different. In terms of total composite lens/sensor resolution, the size of a 2x2 photosite array on the camera's image-sensor matters (if/when the "diffraction spot diameter" resulting from the increased F-Number exceeds the relevant COC diameter). Total composite resolution will be decreased (in part) because the effective pixel-resolution of the recorded image will be reduced.

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olivier_777
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Re: Estimating depth of field
In reply to richarddd, Feb 26, 2013

richarddd wrote:

How do you decide what f-stop to use to get a desired amount of DOF?

Hi

Coming late in the game and I did not read the whole thread, but here is the simple answer:

Just use the subject's width (the long side of your frame, let's call it W) in the following extremely simple rule of thumb. In 43 format,

​DOF = W² * Fstop / 10

​Example: you're shooting a subject 1m wide, at f2.8?

DOF = 1 * 1 * 2.8 / 10 = 0.28m

Could it be simpler?

(Of course, you figured that in portrait mode, W is the height...)

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Anders W
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Re: Estimating depth of field
In reply to richarddd, Feb 26, 2013

richarddd wrote:

Anders W wrote:

richarddd wrote:

Are there any good illustrations showing DOF v. diffraction? For example, a series of landscape shots showing that apparent DOF increases with f-stop, but that at some point diffraction takes over? Or are there too many variables for such a series of photos to be useful?

No, I haven't seen an illustration of both things simultaneously, only of one or the other. But I see no problems of accomplishing one where you could see the trade-off with your own eyes.

Do you have any suggestions for designing and executing such a test?

Just about any "macro" (meaning close-up) scene should do, stopping down from the point at which the lens is at peak (about f/4 is a fast prime) to the minimum that the lens allows (f/22 with MFT usually). A landscape with the foreground beginning really close (or at high magnification) and extends to "practical" infinity (what this is depends on the lens used) would be another option.

What are the main variable in the trade-off between diffraction and DOF?

Only two: Assuming the lens has already been stopped down to its peak resolution at the outset, what will happen as you stop down further is that the DoF will become deeper and deeper but the resolution of things within the DoF increasingly poor. In essence, you buy increased resolution in some places at the expense of less resolution in others. However, if you could stop down far enough, you would eventually reach a point where sharpness would decline across the entire frame so that there would be no increase left to buy anywhere.

"what a small aperture giveth, diffraction taketh away"

Does lens design matter or is aperture the only relevant variable for a given sensor size?

If lens design matters at all, it doesn't matter much. So for a given sensor size, given subject distance, and given FL, I'd say it's about aperture only.

One minor reservation here is that in practice, although not in the world of DoF calculators, the DoF, as judged by your eye, does vary with lens quality. A sharper lens will in practice give more DoF than a less sharp one. You find an example here (see especially the last two paragraphs):

http://forums.dpreview.com/forums/post/50038178



Any thoughts on this calculator, which purports to show, among other measures, DOF v. diffraction. http://www.stegmann.dk/mikkel/barnack/

Haven't seen that before but looks quite interesting so thanks for drawing my attention to it. Looks like it might be quite useful, not for use in the field, but for thinking and discussing about what we might want to do in the field, as we do at the moment.

In this context, would the key numbers be the circle of confusion compared to the diffraction spot diameter, with the idea that once the diffraction spot passes the CoC, there is no further DoF increase?

Again, in the world of DoF calculators, no. They simply don't take diffraction into account. But in the real world, diffraction does of course limit the DoF since in practice it makes the CoC at a certain point bigger than it would otherwise be.

Provided that the diffraction spot diameter and the CoC are directly comparable entities (and I don't know out of hand to which extent that's the case), I guess the point you mention would be the point at which nothing would be within the DoF (since not even a point that is perfectly in focus would have a sufficiently small footprint to pass the CoC criterion) rather than the point at which the DoF ceases to increase.

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Anders W
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Re: look at that!
In reply to Chez Wimpy, Feb 26, 2013

Chez Wimpy wrote:

Anders W wrote:

Things at the edges tend to be closer to the camera (or rather to a plane in front of the camera) than those at the center so that the field curvature in practice helps extend the DoF.

It is interesting that the 24TSEII has pretty pronounced field curvature as well. This is a problem in landscapes with deep DOF (the side of the image near the horizon are usually soft unless you are stopped down a bit), the workaround is to focus with LV on the edges of the shifted image circle and let the center infinity suffer a bit for better consistency.

Hmm. So TS lenses have this problem too. Well, I guess the oversized image circle doesn't exactly make it easier to avoid at least some field curvature. And the way you handle the problem in practice makes eminent sense of course.

There is also a fair bit of image distortion in the complete image circle - but it doesn't much matter with TS landscapes (architecture is different of course) because lens rises and falls the horizon near the straight-line optical center.

Not sure I follow you here. Could you please elaborate a bit. I realize that distortion will be less in the center of the true image circle (not of the crop you use) but ...

Well the wind hits the "prairie" around Uppsala too from time to time, but we do have our quiet moments where focus-stacking a meadow full of spring blossoms wouldn't be much of a problem I would think (still have to try). And imagine the time, soon to come of course , when the camera will bracket focus in burst-mode just as conveniently as it already does when it comes to exposure.

One of the other problems with focus stacking with most DSLR lenses is focus breathing. These are not designed for cinema use, and digital stacking is clearly not in the basic parameters. With the 90TSE and my 70-200/2.8IS in my few (unsatisfactory) attempts, the planes don't match up. There is perhaps as much as a 10% shift in image size (or more precisely focal length change) as you go from close to infinity. I don't shoot macro so I don't know if this is a problem there, or something that can be worked around with automated software (I do my masking by hand).

I admit I didn't think of that possibility. Are you saying this is a problem not only with the 70-200 but also with the 90 TSE? I am aware of course that there can be focus breathing but I thought it would as a rule be noticeable with some macro lenses (which are well-known to alter the FL significantly when getting close to minimum focus distance).

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Detail Man
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Re: Estimating depth of field
In reply to olivier_777, Feb 26, 2013

olivier_777 wrote:

richarddd wrote:

How do you decide what f-stop to use to get a desired amount of DOF?

Hi

Coming late in the game and I did not read the whole thread, but here is the simple answer:

Just use the subject's width (the long side of your frame, let's call it W) in the following extremely simple rule of thumb. In 43 format,

​DOF = W² * Fstop / 10

​Example: you're shooting a subject 1m wide, at f2.8?

DOF = 1 * 1 * 2.8 / 10 = 0.28m

Could it be simpler?

(Of course, you figured that in portrait mode, W is the height...)

Am curious as to how you derived that formula. Could you explain (or provide a reference) ?

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richarddd
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Re: Estimating depth of field
In reply to Anders W, Feb 26, 2013

Manual focus. See EXIF data for other info. At what point do you think diffraction is outweighing a smaller aperture with respect to DOF?



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Anders W
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Re: Estimating depth of field
In reply to richarddd, Feb 26, 2013

richarddd wrote:

Manual focus. See EXIF data for other info. At what point do you think diffraction is outweighing a smaller aperture with respect to DOF?

In this case, I would say it doesn't. The sharpness of things that are not in perfect focus continue to increase all the way to f/22. The diffraction effect for things that are in focus is perhaps discernable but not particularly disturbing in this case.

I've seen macro shooters on this forum report that they don't hesitate to stop down to f/22 in cases where they need all the DoF they can get and it is a prime concern to get it (which might be pretty often when you are doing macro) and your test suggests that this might not be a bad idea. The "don't go beyond f/8" rule has its exceptions like any good rule.

As to the borders of the DoF, I'd say, based on what my eyes rather than the DoF calculator tells me, that the closest jar is entirely within the DoF at f/16. None of the other jars ever is.



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richarddd
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Re: Estimating depth of field
In reply to Anders W, Feb 26, 2013

Anders W wrote:

richarddd wrote:

Manual focus. See EXIF data for other info. At what point do you think diffraction is outweighing a smaller aperture with respect to DOF?

In this case, I would say it doesn't. The sharpness of things that are not in perfect focus continue to increase all the way to f/22. The diffraction effect for things that are in focus is perhaps discernable but not particularly disturbing in this case.

Agreed

I've seen macro shooters on this forum report that they don't hesitate to stop down to f/22 in cases where they need all the DoF they can get and it is a prime concern to get it (which might be pretty often when you are doing macro) and your test suggests that this might not be a bad idea. The "don't go beyond f/8" rule has its exceptions like any good rule.

One general rule of thumb is to stop down as much as needed to get the desired DOF, even if some of the benefits of more DOF are lost due to diffraction. I don't see anything in this test that's contrary to that general rule.

The camera to first subject distance was about 3' and camera to last subject was about 6', which is much further than I normally think of as macro. Focus was on the first subject.

Is there another test that you would expect to yield a different result? If so, what?

As to the borders of the DoF, I'd say, based on what my eyes rather than the DoF calculator tells me, that the closest jar is entirely within the DoF at f/16. None of the other jars ever is.

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Anders W
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Re: Estimating depth of field
In reply to richarddd, Feb 26, 2013

richarddd wrote:

Anders W wrote:

richarddd wrote:

Manual focus. See EXIF data for other info. At what point do you think diffraction is outweighing a smaller aperture with respect to DOF?

In this case, I would say it doesn't. The sharpness of things that are not in perfect focus continue to increase all the way to f/22. The diffraction effect for things that are in focus is perhaps discernable but not particularly disturbing in this case.

Agreed

I've seen macro shooters on this forum report that they don't hesitate to stop down to f/22 in cases where they need all the DoF they can get and it is a prime concern to get it (which might be pretty often when you are doing macro) and your test suggests that this might not be a bad idea. The "don't go beyond f/8" rule has its exceptions like any good rule.

One general rule of thumb is to stop down as much as needed to get the desired DOF, even if some of the benefits of more DOF are lost due to diffraction. I don't see anything in this test that's contrary to that general rule.

The camera to first subject distance was about 3' and camera to last subject was about 6', which is much further than I normally think of as macro. Focus was on the first subject.

Is there another test that you would expect to yield a different result? If so, what?

Not really, as long as meeting certain DoF requirements is critical. In landscape shooting, for example, I might frequently be ready to sacrifice a bit in that regard as far as the foreground is concerned for better sharpness in the distance. I would also think, based on other tests that I have seen, that the loss due to diffraction would be more visible than it is in your test.

As to the borders of the DoF, I'd say, based on what my eyes rather than the DoF calculator tells me, that the closest jar is entirely within the DoF at f/16. None of the other jars ever is.

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richarddd
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Re: Estimating depth of field
In reply to Anders W, Feb 26, 2013

Anders W wrote:

richarddd wrote:

One general rule of thumb is to stop down as much as needed to get the desired DOF, even if some of the benefits of more DOF are lost due to diffraction. I don't see anything in this test that's contrary to that general rule.

The camera to first subject distance was about 3' and camera to last subject was about 6', which is much further than I normally think of as macro. Focus was on the first subject.

Is there another test that you would expect to yield a different result? If so, what?

Not really, as long as meeting certain DoF requirements is critical. In landscape shooting, for example, I might frequently be ready to sacrifice a bit in that regard as far as the foreground is concerned for better sharpness in the distance. I would also think, based on other tests that I have seen, that the loss due to diffraction would be more visible than it is in your test.

What other conditions are likely to result in more visible loss due to diffraction?

Look at the nearest subject from my test, I don't see any loss due to diffraction at f/16. Smaller apertures do show some loss, but only when pixel peeping. I'm looking on my notebook, so a larger monitor may reveal more.

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Anders W
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Re: Estimating depth of field
In reply to richarddd, Feb 27, 2013

richarddd wrote:

Anders W wrote:

richarddd wrote:

One general rule of thumb is to stop down as much as needed to get the desired DOF, even if some of the benefits of more DOF are lost due to diffraction. I don't see anything in this test that's contrary to that general rule.

The camera to first subject distance was about 3' and camera to last subject was about 6', which is much further than I normally think of as macro. Focus was on the first subject.

Is there another test that you would expect to yield a different result? If so, what?

Not really, as long as meeting certain DoF requirements is critical. In landscape shooting, for example, I might frequently be ready to sacrifice a bit in that regard as far as the foreground is concerned for better sharpness in the distance. I would also think, based on other tests that I have seen, that the loss due to diffraction would be more visible than it is in your test.

What other conditions are likely to result in more visible loss due to diffraction?

High contrast along with fine detail. A couple of examples here:

http://www.luminous-landscape.com/tutorials/understanding-series/u-diffraction.shtml

http://www.kenrockwell.com/tech/diffraction.htm

Look at the nearest subject from my test, I don't see any loss due to diffraction at f/16. Smaller apertures do show some loss, but only when pixel peeping. I'm looking on my notebook, so a larger monitor may reveal more.

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richarddd
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Re: Estimating depth of field
In reply to Anders W, Feb 27, 2013

Anders W wrote:

richarddd wrote:

Anders W wrote:

richarddd wrote:

One general rule of thumb is to stop down as much as needed to get the desired DOF, even if some of the benefits of more DOF are lost due to diffraction. I don't see anything in this test that's contrary to that general rule.

The camera to first subject distance was about 3' and camera to last subject was about 6', which is much further than I normally think of as macro. Focus was on the first subject.

Is there another test that you would expect to yield a different result? If so, what?

Not really, as long as meeting certain DoF requirements is critical. In landscape shooting, for example, I might frequently be ready to sacrifice a bit in that regard as far as the foreground is concerned for better sharpness in the distance. I would also think, based on other tests that I have seen, that the loss due to diffraction would be more visible than it is in your test.

What other conditions are likely to result in more visible loss due to diffraction?

High contrast along with fine detail. A couple of examples here:

http://www.luminous-landscape.com/tutorials/understanding-series/u-diffraction.shtml

http://www.kenrockwell.com/tech/diffraction.htm

I'd certainly agree that you need a scene with fine detail in order to have a loss of fine detail due to diffraction

Are conditions under which the general rule of thumb I gave above would be wrong?

Are there conditions under which stopping down results in less DOF due diffraction compared to not stopping down as much?

Look at the nearest subject from my test, I don't see any loss due to diffraction at f/16. Smaller apertures do show some loss, but only when pixel peeping. I'm looking on my notebook, so a larger monitor may reveal more.

Just to state the obvious, f/16 is a smaller aperture than the f/8 cited in this thread.

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