Depth of field: Full-frame lens vs. APS-C lens, both on APS-C sensor

[theraven871]

I compared the same photograph taken with two different cameras (sensor sizes). A comparison that would be interesting and meaningful to a photographer.

You can't take the same photograph with a 50mm lens on a FF camera and also a cropped sensor camera. So if you compare an apple with an orange and proclaim that they're different what was the point of your comparison? My niece would say, "duuuuhhhhhh."

Joe

It's only a comparison that would be interesting to some photographers. Have you noticed we are all talking about different parts of the same thing.

There does seem to be a lot of cross talk going on here. My concern is with this error stated in post #13: "I have full frame and APS-C bodies, and prime lenses, so I got out a tripod, a target and a tape measure. Sensor size has no effect on DOF."

I posted a correction in post #43.

Frequently we make brief statements that are true in certain circumstances, but don't really illuminate sufficiently to permit the information to be used/understood in other situations.

Bokeh comes mostly from focal length, aperture, and distance to subject/distance to background. If a smaller/larger sensor allows you to move with respect to your subject/background, that movement will be what affects the bokeh. Put a 50 mm f/1.8 lens on a crop body, or on a full frame body, and you will be able to go and shoot with the same ISO, same shutter speed, and same aperture, and you will get an image with the same exposure, but different framing. If you want more bokeh, get a full frame body because for any given focal length, you can stand closer and still fit your subject in.

Moving the camera alters perspective and produces a different photograph -- not a valid comparison.

Get a medium format camera because the much larger sensor will let you stand even closer! Standing closer is the part that will deliver more bokeh. Same lens, same distance to subject, same aperture, same DOF, different framing if you have different sensor sizes.

Moving the camera alters perspective and produces a different photograph -- not a valid comparison.

Joe

Joe,
I agree with you.
If you take a 50mm 1.8 lens on a full frame vs crop sensor, you'll need to get CLOSER with the full frame to keep the same composition.
This, of course, will also affect your depth of field. So its not an accurate test.

 

[CameraClicker]

I compared the same photograph taken with two different cameras (sensor sizes). A comparison that would be interesting and meaningful to a photographer.

You can't take the same photograph with a 50mm lens on a FF camera and also a cropped sensor camera. So if you compare an apple with an orange and proclaim that they're different what was the point of your comparison? My niece would say, "duuuuhhhhhh."

Joe

It's only a comparison that would be interesting to some photographers. Have you noticed we are all talking about different parts of the same thing.

There does seem to be a lot of cross talk going on here. My concern is with this error stated in post #13: "I have full frame and APS-C bodies, and prime lenses, so I got out a tripod, a target and a tape measure. Sensor size has no effect on DOF."

I posted a correction in post #43.

Frequently we make brief statements that are true in certain circumstances, but don't really illuminate sufficiently to permit the information to be used/understood in other situations.

Bokeh comes mostly from focal length, aperture, and distance to subject/distance to background. If a smaller/larger sensor allows you to move with respect to your subject/background, that movement will be what affects the bokeh. Put a 50 mm f/1.8 lens on a crop body, or on a full frame body, and you will be able to go and shoot with the same ISO, same shutter speed, and same aperture, and you will get an image with the same exposure, but different framing. If you want more bokeh, get a full frame body because for any given focal length, you can stand closer and still fit your subject in.

Moving the camera alters perspective and produces a different photograph -- not a valid comparison.

Get a medium format camera because the much larger sensor will let you stand even closer! Standing closer is the part that will deliver more bokeh. Same lens, same distance to subject, same aperture, same DOF, different framing if you have different sensor sizes.

Moving the camera alters perspective and produces a different photograph -- not a valid comparison.

Joe

Joe, skip back to #35. Bodies were changed to change sensors, lens, distance and all that were kept the same. I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change. There is no math involved, just a real world test. In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected! How is that a valid comparison. Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.

 

[Braineack]

Joe, skip back to #35. Bodies were changed to change sensors, lens, distance and all that were kept the same. I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change. There is no math involved, just a real world test. In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected! How is that a valid comparison. Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.

when you look, "A" has less DOF.

B and C appear to be the exact same image.

The test in #43 is not very good, the DOF area is already so large than any difference will be hard to measure/see.

The same test at f/2.8 with the 80mm/50mm of a stuffed animal, or something more 3D, filling the frame would be a better test.

 

[Ysarex]

Joe, skip back to #35. Bodies were changed to change sensors, lens, distance and all that were kept the same. I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change. There is no math involved, just a real world test. In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected! How is that a valid comparison. Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.

You're not comparing apples to apples. If the distance didn't change and the lens didn't change then you didn't take the same photo with the FF sensor camera or you cropped the FF camera image in which case I believe Wayne said something like are you joking?

.........f^2
H = -------
.........Nc

The math is simple and the math is clear. Unless you can demonstrate that changing "c" does not change "H" then sensor size is a determinant factor in DOF.

Joe

 

[Derrel]

Goodness gracious, people....sensor size is a MAJOR factor in depth of field!! Do you want to be able to take pictures where objects from fairly close to Infinity are in good focus? Do you want to be able to shoot across a restaurant table AND also have the artwork on the back wall be recognizably in-focus? If the answer is yes, then shoot with a SMALL-sensor camera, like a digital Point & Shoot camera, or your cellphone camera.

Do you want to be able to shoot portraits in a garage studio or a living room studio, where you have only about five feet behind the subject's head to where you must hang your backdrop fabric or paper, and do you want the background to be noticeably OUT of focus? If the answer is yes, this is one of the ********primary*********, actual scenarios where I can almost always spot a DX or APS-C or m4/3 camera, as opposed to an FX sensor camera.

Do you want to shoot pictures of a person full-length, where the background just 20 feet behind them is pretty much unrecognizable? This is **exactly** what a 120 rollfilm camera and its 150mm short telephoto lens can do for you.

Do you want to shoot close-up artistic portraits where the eyes are in focus and the ears are wayyyyyyy out of focus, using flash, at f/5.6? Shoot on 4x5 sheet film. It has an amazing shallow depth of field character that smaller formats simply cannot match.

 

[CameraClicker]

Joe, skip back to #35. Bodies were changed to change sensors, lens, distance and all that were kept the same. I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change. There is no math involved, just a real world test. In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected! How is that a valid comparison. Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.

when you look, "A" has less DOF.

B and C appear to be the exact same image.

The test in #43 is not very good, the DOF area is already so large than any difference will be hard to measure/see.

The same test at f/2.8 with the 80mm/50mm of a stuffed animal, or something more 3D, filling the frame would be a better test.

I had to go back and look at the original files. I still don't see an obvious difference. The target was about 8 feet from the camera, so if sensor size was a major factor, I would expect twice the sensor to make more of a difference. Braineack and Theraven871 did successfully guess the correct file.

Here are the 3 files overlaid, with labels.

 

[CameraClicker]

Joe, skip back to #35. Bodies were changed to change sensors, lens, distance and all that were kept the same. I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change. There is no math involved, just a real world test. In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected! How is that a valid comparison. Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.

You're not comparing apples to apples. If the distance didn't change and the lens didn't change then you didn't take the same photo with the FF sensor camera or you cropped the FF camera image in which case I believe Wayne said something like are you joking?

.........f^2
H = -------
.........Nc

The math is simple and the math is clear. Unless you can demonstrate that changing "c" does not change "H" then sensor size is a determinant factor in DOF.

Joe

Joe, you want to compare apples to apples, then you change focal lengths. These are crummy photos but they should be about the same width. I don't have an 80 mm prime lens so I used a ruler and a zoom. EXIF data says 75 mm, but the ruler says they are about the same width.


................ FF ............................................................. APS-C ............................


So the image fills the frame about the same but I would not say the images are the same. Look at what happens when you take 100% crops, the same size!


................ FF ............................................................. APS-C ............................

If you are printing portraits, your argument and math makes a degree of sense, but if you are doing other things, there are several moving parts to pay attention to.

 

[Ysarex]

Joe, skip back to #35. Bodies were changed to change sensors, lens, distance and all that were kept the same. I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change. There is no math involved, just a real world test. In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected! How is that a valid comparison. Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.

when you look, "A" has less DOF.

B and C appear to be the exact same image.

The test in #43 is not very good, the DOF area is already so large than any difference will be hard to measure/see.

The same test at f/2.8 with the 80mm/50mm of a stuffed animal, or something more 3D, filling the frame would be a better test.

I had to go back and look at the original files. I still don't see an obvious difference. The target was about 8 feet from the camera, so if sensor size was a major factor, I would expect twice the sensor to make more of a difference. Braineack and Theraven871 did successfully guess the correct file.

Here are the 3 files overlaid, with labels.
View attachment 87472

You're using the same lens from the same position on a FF and crop sensor camera -- you're cropping the FF sensor then and so this is a comparison of DOF between a crop sensor and a crop sensor -- you're proving that two crop sensors have the same DOF. Going to have to quote my niece again....

What you need to do is compare a FF sensor with a crop sensor by taking the same photo with each.

.........f^2
H = --------
.........Nc

You can't calculate DOF without the variable circle of confusion -- "c". "c" is a variable so it's value changes. The variable value of "c" changes with sensor size. Change sensor size and you change "c" in the above equation. Change "c" and you change "H". It can't get any clearer than that.

Joe

 

[CameraClicker]

Joe, you may have to quote your niece again. LOL!

Let me run this by you.
Here are DOF calculator results for what I did:

So on the calculator it says "Use the actual focal length of the lens". So I use some APS-C body to take a picture. Then I use a full frame body, from the same place, same ISO, same aperture, same lens. The calculator says APS-C should be total depth of 0.09 ft, or 1.08 inches. It says the full frame should have more DOF, 0.14 ft, or 1.68 inches -- 56% more!

When I take those photos and look at the results, , I don't see 56% more! A couple of people here have said they see less, maybe, with full frame.

In my world, mathematical modeling is supposed to produce a result that you can get out a ruler and measure. The experiment is not showing what the calculator seems to be predicting.

 

[Braineack]

look at the foreground DOF.

The 4 is soft on the 5D but sharp on the crop bodies.

If I overlay the two images, and then match the black hash marks to the left of the numbers to each other and move the rows so the blur matches between the two, that lines up the 6 of the crop bodies to the 3 of the full-frame.

that looks to be about a half inch distance between the two.

here's a screen shot:

 

[shefjr]

I don't know if anyone has seen this but, I thought it was a nice illustration kundalini did her on TPF. I haven't read all of the discussion so I'm posting this up after only reading the thread title.

So You Wanna See the Difference Between Full Frame and Cropped Sensors? | Photography Forum

I hope it is helpful. It really was for me.

 

[CameraClicker]

look at the foreground DOF.

The 4 is soft on the 5D but sharp on the crop bodies.

If I overlay the two images, and then match the black hash marks to the left of the numbers to each other and move the rows so the blur matches between the two, that lines up the 6 of the crop bodies to the 3 of the full-frame.

that looks to be about a half inch distance between the two.

here's a screen shot:

There's gotta be a better way to evaluate this! I overlaid the files and masked out a strip so I can see the full frame on my left and APS-C on the right. It looks like moving the crop file up one character so the FF '0' and crop foreground '1' align, then from front to back, they look even to me. Probably time for new eyes, their warranty was up years ago.

You seem to be saying there may be a half inch less DOF in the full frame file? The calculator says the full frame should be sharper for half an inch!

 

[Braineack]

Oh wait all were shot at same spot and focal length and the full frame was cropped to match?

 

[runnah]

I am getting a strong sense of déjà vu.

 

[shefjr]

I am getting a strong sense of déjà vu.

Does that mean that this thread is gonna "make my dick itch?"
I went through the thread I recommended and see that Brianeack was involved in that thread trying to discuss this topic with WayneF.