All poppycock.

I have always carried around my Eastman hyperfocal distance chart (yellow, plastic credit-card-size) - essential when you have to shoot wild and no assistant to pull focus. All I need.

A Normal lens is an arbitrary reference point so you can talk about lenses ("give me a wide" takes on a meaning).

Amazing how - apart from comparing modern lenses - we manage to re-invent a 3,000-year-old old wheel.

@alcomposer lol. Actually, now that you have mentioned the nazis, I have to confess that it was the mustached guy himself that once visited me in a dream and explained to me that all this "normal lens" and "z axis distortion" talk was part of a Zionist conspiracy. ;)

Ok... Maybe just the Nazi thing:

http://en.wikipedia.org/wiki/Godwin's_law

If anything the below chart sums up 'trash talk flame war' cause.

@VK isn't there the rule that given enough time 'every' thread on any forum will eventually turn into either a Flame war and/or an argument based on Nazi's?

I even think there is a term for this phenomenon.

In case anyone is interested, I posted this over at dpreview.com as well.

http://forums.dpreview.com/forums/readflat.asp?forum=1041&thread=42027675&page=1

They have taken this idea, much farther than I could have imagined. Its a great discussion on a whole slew of perspectives relating to DOF.

Thanks again everyone for your comments!!

@stonebat I did get a nice semi-macro, high DOF shot with the Panny 14mm prime at MFD. I bet the close-up adapter would really do the trick, great for my bug movie.

@stonebat My apologies if you took my rant as a personal attack. It wasn't meant to be. In all seriousness, I've been a victim of that myth for years before finding out what was all about. And no, x and y axis distortion are all another matter, but seriously, I don't want to convince anyone, hopefully Anton Wilson will. I was just trying to be of help by pointing people to a very interesting read.

Peace.

There's a zillion examples of all lenses at all apertures in stills and videos online. Throw the theory out the window and just browse for the "look" you want. My Vivitar 58 and Russian 58mm have a totally different look, different bokeh, different edges, different shadow detail, contrast, color and so on. The difference is startling, and click the aperture ring one stop and yet another "look" as the iris changes shape. Move the cam forwards and back so the FOV is the same as another lens, and yet again, a different look for the same FOV. Plug the cam into a big, flat screen TV and start playing around with the lenses. Learn the look, pick the lens, adjust the settings. If shallow DOF is what you want, don't get the 14mm :)

Nice gif. to follow Vitaliy,

One dolly zoom to rule them all, one dolly zoom to find them One dolly zoom to bring them all an on their keyboards make them vomit ;)

I'd use 75mm 1.8 instead of 20mm 1.7 if I want a long shot with very blurred background in a city street. The longer focal length, the larger circle of confusion, the shallower DOF.

"Long focal length lenses, also called telephotos, have a narrower field of view than normal and wide angle lenses, and compress space along the z axis of the frame. Because of this, telephoto lenses appear to bring the background of an image closer to the foreground, flattening space; movement along the z axis is also distorted." - The Filmmaker's Eye

Here's the z axis distortion.

Depth of field has everything to do with resolution. The image projected by the lens is sharper for objects that are closer to the focal plane, but within the focus field, everything looks equally in-focus because the circles of confusion are smaller than the output pixels. It's only when the circles of confusion start to be bigger than the output pixels that we start to see them as circles instead of as points or pixels. Typically for depth of field calculations you use a circle of confusion diameter criterion equal to the output pixel pitch.

It's not just theoretical. It totally bears out in practice, and there's a huge difference between the resolution of the GH2's 16-megapixel stills and the 1-2 megapixel video.

Don't confuse depth of field with bokeh size. You can get bigger bokeh with larger aperture lenses and/or close objects, independent of the resolution.

I would not say any of those lenses is really great for DOF, and the 14mm are hyperfocal. Check out this Leica 75/1.4 video

@psyco You are thinking about cropping FOV. But the longer focal length distorts the z-axis which brings the background closer which gives shallow DOF. e.g. Bokeh will be bigger.