Depth of Field calculator inconsistencies: Like many here I have used the Dofmaster online site for DoF calculations. Over time I have also downloaded and tried out a variety of DoF...

mwsilvers Loc: Central New Jersey

Like many here I have used the Dofmaster online site for DoF calculations. Over time I have also downloaded and tried out a variety of DoF apps for my Android phone. What I had quickly discovered was that the results from the Android apps almost all differ from each other as well as from Dofmaster, sometimes by large amounts. Most of the time, the difference is not significant enough to cause any problems. However, I wonder if others have seen the same thing, can identify the best phone app to use, and explain why the calculations would differ from app to app and to Dofmaster. In my ignorance, I would assume that these calculators are using standard DoF algorithms. I have searched online on several occasions but have not yet found a useful answer

blackest Loc: Ireland

mwsilvers wrote:

Like many here I have used the Dofmaster online si... (show quote)

Depth of field tends to be acceptable depth of field , whats acceptable? Circle of Confusion is one parameter, so there will be differences between camera bodies. Perhaps the wrong values are being used.

mwsilvers Loc: Central New Jersey

blackest wrote:

Depth of field tends to be acceptable depth of field , whats acceptable? Circle of Confusion is one parameter, so there will be differences between camera bodies. Perhaps the wrong values are being used.

All the apps have settings for specific bodies. And yes perhaps the wrong values are being used. But almost every one of these apps differs from each to some degree. I'd be curious to know which is the most accurate.

wdross Loc: Castle Rock, Colorado

mwsilvers wrote:

Like many here I have used the Dofmaster online si... (show quote)

blackest point about circle of confusion is a big one. Although it should be somewhat standardized, some may choose a slightly different data base. Then each program needs to be examined for number of decimal places used and rounding errors.

mwsilvers Loc: Central New Jersey

wdross wrote:

blackest point about circle of confusion is a big one. Although it should be somewhat standardized, some may choose a slightly different data base. Then each program needs to be examined for number of decimal places used and rounding errors.

I understand that the number of decimal points will make a difference. But the differences I see seem to be going way beyond that.

BebuLamar

The size of the COC is not consistent across the apps. That is one of the reason. If the app allows you to change it then make sure all your apps use the same value.

selmslie Loc: Fernandina Beach, FL, USA

mwsilvers wrote:

Like many here I have used the Dofmaster online si... (show quote)

A DOF calculator with the best explanation is at Cambridge in Colour: https://www.cambridgeincolour.com/tutorials/dof-calculator.htm

All DOF calculators use (or should use) the same formulas. The difference is primarily in the assumption about the size of the COC. But there are other factors that come into play as you will learn from their documentation.

wdross Loc: Castle Rock, Colorado

mwsilvers wrote:

I understand that the number of decimal points will make a difference. But the differences I see seem to be going way beyond that.

The formula for DOF is somewhat lenghty. Some may have "simplified" certain sections that they felt had only a "small" effect on the DOF. This would allow the app to function faster

mwsilvers Loc: Central New Jersey

selmslie wrote:

A DOF calculator with the best explanation is at Cambridge in Colour: https://www.cambridgeincolour.com/tutorials/dof-calculator.htm

All DOF calculators use (or should use) the same formulas. The difference is primarily in the assumption about the size of the COC. But there are other factors that come into play as you will learn from their documentation.

Thanks to you and the other responses.. I will check out the link. So is the main issue that circles of confusion are not an absolute calculation? Do any of you know if there Is an app or apps that is more "accurate" than others regarding CoC?

BebuLamar

mwsilvers wrote:

Thanks to you and the other responses.. I will check out the link. So is the main issue that circles of confusion are not an absolute calculation? Do any of you know if there Is an app or apps that is more "accurate" than others regarding CoC?

The reason is that there are several definitions of the COC.

selmslie Loc: Fernandina Beach, FL, USA

mwsilvers wrote:

Thanks to you and the other responses.. I will check out the link. So is the main issue that circles of confusion are not an absolute calculation? Do any of you know if there Is an app or apps that is more "accurate" than others regarding CoC?

After you visit Cambridge in Colour you should have the answer. Remember to click on show advanced to see what else is involved.

mcveed Loc: Kelowna, British Columbia (between trips)

The depth of field is that range in which the image is "acceptably sharp". What is acceptable? That is determined by the "circle of confusion" but the size of the CoC is not standard. It should be, perhaps. The Cambridge notes on their DOF calculator are very thorough and will explain why all calculators are not the same.

selmslie Loc: Fernandina Beach, FL, USA

mcveed wrote:

The depth of field is that range in which the image is "acceptably sharp". What is acceptable? That is determined by the "circle of confusion" but the size of the CoC is not standard. It should be, perhaps.

It can't be standard. See the above link.

wdross Loc: Castle Rock, Colorado

mwsilvers wrote:

Thanks to you and the other responses.. I will check out the link. So is the main issue that circles of confusion are not an absolute calculation? Do any of you know if there Is an app or apps that is more "accurate" than others regarding CoC?

You might want to compare the apps to each other and see which ones come closest to each other. Then, using one of them, setup targets on a tape measure, see where the targets look "sharp", and see which one of the app comes closest to what you find. That will be the most accurate for you and your vision.

mcveed Loc: Kelowna, British Columbia (between trips)

It's all approximate anyway. How accurate are you at judging the distance to your subject? If you're out a couple of yards your DoF will be slightly off too.