Is shallow DOF a phase? asking for advice on my future photography

Started Sep 23, 2012 | Discussions thread
JLRX
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Re: Is shallow DOF a phase? asking for advice on my future photography
In reply to Rich42, Sep 25, 2012

I've had to read your post a couple of times to see what was wrong with your statement.

The size of the sensor (or film for that matter) has absolutely NOTHING to do with DOF (shallow or deep). How come there NEVER was any such claim comparing 35 mm (or smaller) film cameras to large format cameras? NEVER! EVER!

Since the size of the sensor/film is dependent on the lens being used to project the image upon it, I would say that it's a big part of the equation.

It is perfectly possible to make an 8x10 print (or any other size print) from a small digital point and shoot and from an 8x10 view camera and have the DOF exactly the same in both prints. The only thing that can't be the same ("all other things being equal") is the Image Quality of the resulting prints. If good technique is used with both cameras, the 8x10 view camera print IQ will always beat the small camera IQ. But DOF WILL be the same, IF THE SAME CONDITIONS PREVAIL IN BOTH SHOOTING SITUATIONS.

At equal lens FOV for each format (lets say 50mm for 35mm and a 300mm for 8X10) and at the same camera to subject distance (since both lenses have the same FOV there is no reason to change the distance) the 8x10 will have less DEF at the same aperture. If you want the same DOF you will have to close the 8x10 by about 6 f stops, f/5.6 on 35mm = f/45 on 8x10 for lenses have the same DOF.

If both a small camera and an 8x10 camera are fitted with "normal lenses" (defined below), both shoot at the same aperture, and both are positioned to place the image on the sensor (film) in an equivalent way, prints made to the same size from both will show absolutely identical DOF.

NOPE, there are about six stops difference. Imagine you are photographing a person from a distance of 5 meters with a 35mm camera, you have two lenses: a 50mm and a 300mm and you are shooting at f/5.6. With the 50mm you are going to have more DOF and a bigger FieldOfView. You are going to capture that person full length and a lot of the background in focus. With the 300mm at the same distance you are going to capture only the face and have almost no DOF (300/50=6 stops less to be exact). Now, that same lens on 8x10 (it's an 8x10 lens with an adapter to shoot 35mm, just in case you are wondering) will have the same FOV as the 50mm AND the same DOF as the face shot (since a 300mm is a 300mm independent of format, only difference being coverage).

There is one thing that WON'T be the same, and this is where most people get tripped up about the whole topic. Looking at each camera as it is set up to get the model's head correctly imaged in the viewfinder (therefore on the film/sensor), the large camera WILL BE FURTHER AWAY FROM THE SUBJECT than the small camera. This difference in camera placement creates the equivalent shooting conditions.

Why would the larger camera be further away from the subject?!?!? If both cameras have the same 45-50 degree angle of view there is no need to move the larger camera further away from the subject, this doesn't make any sense .

The mistake is to stand at the SAME camera to subject distance, and take pictures with different sized cameras from there and make conclusions about the results. Under that condition, the large camera will appear to have less DOF. It doesn't. It simply has been moved closer to the subject than it should be and "everything else being equal" has been changed to "everything else is not equal."

This, also, is where you don't make sense : If both cameras have the SAME FOV you have to have the SAME camera to subject distance or else it is a different picture.

The closer the camera is to the subject, the less the resultant DOF in the print.

This is an incomplete phrase, you need to state more variables to make it correct, or else: I can be closer to the subject with a fisheye and have more DOF than with a 300mm far away at the same f/stop.

Leave sensor size out of the equation, but make EVERYthing else equal (that optical rules require) and equal apertures result in equal DOF.

This, in essence, is true but then you are ignoring the other variable: FOV. If I use a 250mm, on both 35mm and 8x10, (ignoring the format) and everything else being equal I get equal DOF but very different FOV .

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