D7100 crop mode and depth of field

[o hey tyler]

Then why does a crop sensor have a different DOF than a full-frame one when all else is the same?

Because on a crop sensor, you are framing the same shot at a different distance than you would with a full frame body. If the D7100 has crop lines for the smaller format size, you would have to move back to frame the same shot. If you chose not to move, and just engaged the crop mode, the DOF would be the same but the resolution would be smaller.

Since you have a full frame camera, take a photo of a ruler with a macro lens. Go for 1" of DoF. Crop that image as much as you would like, the depth of field doesn't change from 1".

 

[AaronLLockhart]

Then why does a crop sensor have a different DOF than a full-frame one when all else is the same?

Because on a crop sensor, you are framing the same shot at a different distance than you would with a full frame body. If the D7100 has crop lines for the smaller format size, you would have to move back to frame the same shot. If you chose not to move, and just engaged the crop mode, the DOF would be the same but the resolution would be smaller.

Since you have a full frame camera, take a photo of a ruler with a macro lens. Go for 1" of DoF. Crop that image as much as you would like, the depth of field doesn't change from 1".

^ Those are personally my thoughts.

However, I was waiting on someone to say something else so that I didn't say something and then someone come in and tell me I was an idiot for posting "noob" comments. (Not implying what you said was noob, Tyler. However, if the comment would have come from me, it would have certainly been dismissed as such.)

 

[o hey tyler]

^ Those are personally my thoughts.

However, I was waiting on someone to say something else so that I didn't say something and then someone come in and tell me I was an idiot for posting "noob" comments. (Not implying what you said was noob, Tyler. However, if the comment would have come from me, it would have certainly been dismissed as such.)

I am just a noob dude. Don't give me too much credit.

 

[480sparky]

Then why does a crop sensor have a different DOF than a full-frame one when all else is the same?

Because on a crop sensor, you are framing the same shot at a different distance than you would with a full frame body. If the D7100 has crop lines for the smaller format size, you would have to move back to frame the same shot. If you chose not to move, and just engaged the crop mode, the DOF would be the same but the resolution would be smaller.

Since you have a full frame camera, take a photo of a ruler with a macro lens. Go for 1" of DoF. Crop that image as much as you would like, the depth of field doesn't change from 1".

No, I'm not framing anything different. I'm standing in the same spot. I just use the same lens at the same aperture on two difference cameras.

Try taking a DOF calculator and punching in some numbers with a crop sensor camera. Now change ONE THING: use a full frame. Why is the DOF suddenly different?

 

[AaronLLockhart]

Then why does a crop sensor have a different DOF than a full-frame one when all else is the same?

Because on a crop sensor, you are framing the same shot at a different distance than you would with a full frame body. If the D7100 has crop lines for the smaller format size, you would have to move back to frame the same shot. If you chose not to move, and just engaged the crop mode, the DOF would be the same but the resolution would be smaller.

Since you have a full frame camera, take a photo of a ruler with a macro lens. Go for 1" of DoF. Crop that image as much as you would like, the depth of field doesn't change from 1".

No, I'm not framing anything different. I'm standing in the same spot. I just use the same lens at the same aperture on two difference cameras.

Try taking a DOF calculator and punching in some numbers with a crop sensor camera. Now change ONE THING: use a full frame. Why is the DOF suddenly different?

Because the physical sensor is larger. Which is the point. When you have the same sensor area... DoF shouldn't change. (Or so I would think).

It's not like the camera is flipping back and forth between two separate sensors. It's the same sensor, with the same area, and if the "print size" is the same, then it would use the same number of active pixels, just change the "crop factor." Crop factor could be changed in a camera simply by having a mechanism that moves the sensor closer and further from the back lens element (I'm not saying that is how full frame switch between full frame and crop frame modes, just implying that it COULD be done that way). This wouldn't change the depth of field, only the crop area.

 

[480sparky]

Full Frame:

Crop Sensor:

Once again I will ask: If the sensor size makes no difference as to DOF, then why does every DOF calculator need the sensor size in order to figure DOF?

 

[Vtec44]

Once again I will ask: If the sensor size makes no difference as to DOF, then why does every DOF calculator need the sensor size in order to figure DOF?

It makes a difference when you have two different sensors. However, I don't think cropping mode changes the sensor size but just changes the image size on the exact same sensor.

BTW, the D7000 is front focusing.

 

[480sparky]

.............BTW, the D7000 is front focusing.

I tried not to move the focus ring, but I may have when I changed cameras.

I went round and round in this thread, and I'm still confused.

 

[TheLost]

Somebody correct me if i'm wrong (and i'm sure somebody will)...

But DOF is due to the angle of light coming through the aperture:

Now if you look at FX vs. DX you'll see why FX has a slightly better DOF:

So ends my lesson on DOF!

As to the D7100 crop mode:

My answer is.... No! On the D7100 1.3x crop mode has no affect on DOF. Why? because the light is still hitting the sensor at the same angle. The sensor is just ignoring the data from the outside (to created the 1.3x crop). As somebody said before... 1.3x crop on the D7100 is EXACTLY the same as cropping the image in software. However, The camera is moving less data around so it speeds things up (FPS and buffer flushing).. that is the benefit of having the body do it for you.

(waiting for everybody to tell me where im wrong... going to get popcorn.. brb)

 

[crimbfighter]

480sparky,

What was your camera to subject distance on your test shots, or were either of these images cropped? I only ask because both images have the same FOV, which would lead me to believe you moved the camera to obtain the same FOV, or cropped the images. Obviously, if the camera to subject distance changed, it would effect the focusing distance, which would effect the DOF at any given aperture, explaining why the DOF got larger if you moved the camera farther from the ruler to obtain the same FOV. Certainly don't mean to sound condescending, just trying to wrap my own head around it, as well..

 

[480sparky]

480sparky,

What was your camera to subject distance on your test shots, or were either of these images cropped? I only ask because both images have the same FOV, which would lead me to believe you moved the camera to obtain the same FOV, or cropped the images. Obviously, if the camera to subject distance changed, it would effect the focusing distance, which would effect the DOF at any given aperture, explaining why the DOF got larger if you moved the camera farther from the ruler to obtain the same FOV. Certainly don't mean to sound condescending, just trying to wrap my own head around it, as well..

They were shot from the same spot. Ruler is on a table, cameras on tripod. The only thing I changed was the camera. I then edited them in post to make them the same size & FOV.

 

[crimbfighter]

480sparky,

What was your camera to subject distance on your test shots, or were either of these images cropped? I only ask because both images have the same FOV, which would lead me to believe you moved the camera to obtain the same FOV, or cropped the images. Obviously, if the camera to subject distance changed, it would effect the focusing distance, which would effect the DOF at any given aperture, explaining why the DOF got larger if you moved the camera farther from the ruler to obtain the same FOV. Certainly don't mean to sound condescending, just trying to wrap my own head around it, as well..

They were shot from the same spot. Ruler is on a table, cameras on tripod. The only thing I changed was the camera. I then edited them in post to make them the same size & FOV.

Understood. That blows my theory out of the sky...

 

[Derrel]

Yes, the crop-mode on the D7100 will change the depth of field. Not by a whole heck of a lot, but a small amount. At each given picture angle, you will have more depth of field when shooting to a smaller sensor than you will when shooting to a larger sensor. Now that the base MP count is 24MP, and the crop-mode is a healthy 16 MP in the D7100, that makes for a kind of nifty feature. Nikon has offered multi-size captures for some time now. Where it REALLY comes in handy is when shooting events, or long-lasting things like say, baseball games, or multi-hour events. And it's VERY handy when you have say, a shortish zoom lens, like an 18-35 or 18-55, or whatever, and you'd like to get some frame-filling, or narrow-angle-of-view shots, right in-camera. Just use the crop-mode!

Depth of field changes with the size of the recorded image field; a smaller image sensor, or smaller film, has MORE depth of field at a given picture angle than does a larger film or sensor capture shooting the same picture angle. For example, a semi-wide angle field of view shot at f/4.5 on a P&S with the teeeenie-tiny, pinky-fingrnail-sized sensor has great depth of field when the lens is focused at 5 feet. An APS-C camera, not nearly so much. A 24x36mm camera has even less DOF. A 120 rollfilm SLR shooting 6x9 cm images has VERY little DOF when shot at f/4.5 at 5 feet.

6x9 cm film with a 65mm lens at 5 feet at f/4.5. DOF is 1.1 feet total DOF, from 4.51 feet to 5.61 feet.

An APS-C sized capture shot with a 20mm lens at 5 feet at f/4.5 is 3.85 feet total DOF, from 3.74 to 7.55 feet.

Both cameras will have "similar" picture angle of view.

 

[jl1975]

Thanks everyone for the responses. Nothing like a little lively discussion, right? I'll be sure to experiment with it once I have the camera.

 

[nmoody]

Please excuse the horrid pictures, this was quick and dirty and the only ruler I own. I have a D7100 and have taken two shots. One with 1.3x from mode and the other DX (as it is labeled in the camera) Exif data is intact so you can see my settings.

1.3x

DX