Depth of field question: I'll bet this question has been asked many times here, but I am going to craft it to get the answer I am looking for. I have a number of lenses which can be...

Chefneil

I'll bet this question has been asked many times here, but I am going to craft it to get the answer I am looking for.

I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?

jerryc41 Loc: Catskill Mts of NY

Chefneil wrote:

I'll bet this question has been asked many times here, but I am going to craft it to get the answer I am looking for.

I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?

Aperture is the main factor that determines DoF, but focal length, lens brand and model, and the camera's sensor size can also affect DoF.

LensWork

Yes, given your parameters (same aperture and camera to subject distance, the rest has no effect on DOF), all of the lenses at (true) 90mm will have the same depth of field. What you may find is that the marked 90mm setting on each lens may, or may not, actually be 90mm.

RickL Loc: Vail, Az

That is an excellent question. Depth of field is determined by the aperature setting, the brand should not affect it. High number(F/18) greater depth of field, low number (F/1.8) low depth of field.

AnthonyBiss Loc: Toronto, Ontario

AS NOTED HEREIN THE DOF IS A FUNCTION OF THE F # ON ANY LENS YOU QUOTED.

rmalarz Loc: Tempe, Arizona

DOF is a characteristic of the focal length and aperture. It does not vary from manufacturer to manufacturer. So, yes the DOF will be the same.
--Bob

Chefneil wrote:

I'll bet this question has been asked many times here, but I am going to craft it to get the answer I am looking for.

I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?

Chefneil

LensWork wrote:

Yes, given your parameters (same aperture and camera to subject distance, the rest has no effect on DOF), all of the lenses at (true) 90mm will have the same depth of field. What you may find is that the marked 90mm setting on each lens may, or may not, actually be 90mm.

Indeed, I have been reading lately about some lenses not giving an accurate focal length reading. Thanks LW, for your take on this.

Chefneil

rmalarz wrote:

DOF is a characteristic of the focal length and aperture. It does not vary from manufacturer to manufacturer. So, yes the DOF will be the same.
--Bob

Nice, clear and precise answer, Thanks!

Chefneil

This place is a great resource to those of us who are curious. Lots of good answers here!!!

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Chefneil wrote:

I'll bet this question has been asked many times here, but I am going to craft it to get the answer I am looking for.

I have a number of lenses which can be used at a certain, or common focal range: Canon 24-105, Tamron 90mm macro, and Canon 75-300 F4-F5.6. Everything being equal, 90mm focal length, F11, ISO, shutter speed and distance to subject: Will the depth of field be the same with all of these lenses? Or, does it change with different brands and kinds of lens?

image magnification, sensor size (circle of confusion, actually), aperture. These are the primary determinants. Print or image viewing size, viewer eyesight, are the secondary ones.

At the same magnification and aperture and on the same sensor size, the DoF will be identical regardless of what lens you are using, or who makes it.

This explains it in great detail:

https://en.wikipedia.org/wiki/Depth_of_field

Don't take any wooden nickels from false prophets that may tell you otherwise

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Chefneil wrote:

This place is a great resource to those of us who are curious. Lots of good answers here!!!

But so far, no one has provided the correct and complete answer, or a link to support their opinion.

Or as Dean suggests, test it for yourself. But it will be a little hard to do, since you don't always know what the magnification or focal length is, since lenses often shorten the focal length at close to the minimum focus distance (focus breathing).

Chefneil

Gene51 wrote:

image magnification, sensor size (circle of confus... (show quote)

DeanS Loc: Capital City area of North Carolina

A simple test using all your stated lens all set to same focal length and aperture will give you a direct answer on the spot. You are not likely to notice any discernable diff in results.

camerapapi Loc: Miami, Fl.

In full agreement with Lens Work.

Chefneil

DeanS wrote:

A simple test using all your stated lens all set to same focal length and aperture will give you a direct answer on the spot. You are not likely to notice any discernable diff in results.

Indeed, as I was reading through these posts that project came to mind. I'm going to do that and post results. I'm not sure when I'll be able to do so due to work and general Life, but I will...