Talk about a general assumption. "some instances" hardly applies to most photographers. How about the general assumption that for 100 years, most portrait photographers have coped just fine with DOF without having to use an f2 or f2.8 lens, and most certainly without having a clue about sensor sizes
For the last 100 years the majority of portrait photographers have used large and medium format cameras for their portraiture. The DOF of the larger formats are even less than 35mm and didn't require f/2 of /2.8. Why do you suppose many large format lenses stop down to f/90 and even f/128? Do you think that is to introduce more diffraction to soften the picture because it has so much DOF? It would help your argument if you had some understanding of the history of photography and a working knowledge of large format photography.
I'll wager that most of them don't care about narrow DOF let alone sensor size. They're perfectly happy with everything in the image sharp.
I'll wagger you're wrong. In my adult education classes, where the majority of students have P&S cameras, some of the most frequently asked questions are how to get better portraits and why don't their pictures look more like professional portraits. The students recognize the difference in their images, they just don't know that it's DOF and the limitations it imposes.
Imagemaster wrote:
How about the general assumption that for 100 years, most portrait photographers have coped just fine with DOF without having to use an f2 or f2.8 lens, and most certainly without having a clue about sensor sizes
Of course. But they weren't as clueless as you suggest. They used large format cameras. That is the whole point of this discussion. Sensor (including film) size matters.
On a 4x5 camera, a 260mm lens has about 30 degrees angle of view, about what an 80mm has on a 35mm camera, a nice perspective for portraits. At a 3 meter distance, which gives nice framing for an upper body portrait, the depth of field at f5.6 goes from 2.94 to 3.06 m or about 118 mm (about 4 1/2 inches), a pleasing depth of field from the ears to the tip of the nose.
Sensor size matters and drastically affects depth of field, even if you and some other photographers don't think about it when photographing.
And while you are at it not thinking about it, why don't you and others drop the ad hominem attacks on those of us who do think about it, calling into question our skill as photographers. We have not questioned your skill as a photographer, only your technical understanding. If we choose to study and understand the mathematics it means we have extra tools and understanding at our disposal. It is not a "joke" and we are not "stuck in a mathematical rut". If you want to group yourself with the skill set of the mass of photographers who use point & shoot cameras and don't think about sensor size, you can. Or you can look at the facts as we have laid them out for you and others and learn that sensor size matters. For you to heap scorn on us while you choose to remain ignorant of and dismissive of the mathematics doesn't prove your case or make you look wise.
Jeff Donald wrote:
I'll wagger you're wrong. In my adult education classes, where the majority of students have P&S cameras, some of the most frequently asked questions are how to get better portraits and why don't their pictures look more like professional portraits. The students recognize the difference in their images, they just don't know that it's DOF and the limitations it imposes.
What percentage of photographers have the gumption to take a class on photography? Probably in the single-digit percent range. The rest, therefore, don't know or care.
DOF is a perceived quantity - it's value is always given relative to a set of assumptions. Just as the physical aperture, and focus distance affect depth of field, so does image enlargement and viewing distance. Since image enlargement is as much a function of the sensor/film size, as it is the final print/display size, they all affect the perceived DOF. Any DOF table with fixed values for different focal lengths/f-stop/focal-distance combinations, assumes a certain print size and viewing distance - for a given medium (i.e. 35mm film).
