Depth of Field

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ron - 17 Apr 2007 14:48 GMT

I have just posted the first of a two part series on depth of field.
The article can be found at my site at:

http://ronbigelow.com/articles/depth-of-field-1/depth-of-field-1.htm

Other articles can be found at:
http://ronbigelow.com/articles/articles.htm

Ron Bigelow
http://ronbigelow.com

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Gautam Majumdar - 17 Apr 2007 19:24 GMT

> I have just posted the first of a two part series on depth of field. The
> article can be found at my site at:

Thanks Ron.

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gautam

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cmyk - 20 Apr 2007 09:44 GMT

Crap claims, like:
. A typical assumption for a full-frame digital camera or a 35mm film camera is that the photographer will make an 8"x10" inch print
that will be viewed at about 12"
. An 8"x10" print has a diameter of 325.28mm.
. A full sized sensor is 24mm x 36mm and has a diameter of 43.27mm
. Well, the human eye can resolve about four lines per mm (up close).
. That means that the human eye can barely see a circle with a diameter of about 0.25mm. Any circle with a diameter smaller than
that will appear as a point. ... So, a 0.25 mm circle on an 8"x10" print would barely be recognizable.
make the lot worse than useless IMNSVHO.

Since when is an 8"x10" print typical? In the real world, they probably account for less than 0.1% of prints. Plus the accepted
industry standard for distances in 14" - and that's for 6"x4", not the larger prints that most people view from farther away.

An 8"x10" print has a DIAGONAL of 325.28mm - not a diameter of 325.28mm. Its rectangular, not circular.

Likewise, a full-sized 35mm film has a DIAGONAL of 43.27mm - not a diameter of 43.27mm, and you'd have to enlarge it to 8"x12" (ie
8.47 times, not the 7.5 times you implied) before you could crop an 8"x10" print from it.

As for the a 0.25mm circle, and your 4lines/mm claim, that translates to a measley 100dpi. Try printing any 8"x10" photo at 100dpi
and see if its good for anything other than throwing in the bin - certainly no good for viewing from 12"!! At that distance you need
at least 300dpi for a decent print.

Kind of makes a mockery of your nice neat maths.

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cmyk

>I have just posted the first of a two part series on depth of field.
> The article can be found at my site at:
[quoted text clipped - 6 lines]
> Ron Bigelow
> http://ronbigelow.com

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Paul Furman - 28 Apr 2007 06:40 GMT

cmyk wrote <snippage has occurred>:

> Crap claims, like:
> . Well, the human eye can resolve about four lines per mm (up close).
[quoted text clipped - 8 lines]
> standard for distances in 14" - and that's for 6"x4", not the larger
> prints that most people view from farther away.

Nothing like constructive criticism eh? Crikey man, I thought the
articles were a pretty good stab at the topic, your refinements are a
useful contribution if not for the harsh tone. I think Ron's assumptions
were about right for common practical 35mm/APS useage, of course there
are further standards one might apply but the general gist was covered
and thanks for a 'little more critical' perspective. 'Generally' 35mm is
really only perfect up to around 8x10 and anything like a 24x36 print is
a stretch. Personally I print 13x19 from 10MP but 6MP isn't much
different & even some of my old 3.3MP shots hold up at 13x19 (or cropped
new shots). Given that this is an APS format discussion group, I think
his assumptions were very reasonable for average use.

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Paul Furman Photography
http://www.edgehill.net/1
Bay Natives Nursery
http://www.baynatives.com

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cmyk - 28 Apr 2007 11:15 GMT

> cmyk wrote <snippage has occurred>:
>
[quoted text clipped - 13 lines]
> Personally I print 13x19 from 10MP but 6MP isn't much different & even some of my old 3.3MP shots hold up at 13x19 (or cropped new
> shots). Given that this is an APS format discussion group, I think his assumptions were very reasonable for average use.

APS format discussion group??
rec.photo.digital.slr-systems

AFAIK there are no true APS format DSLRs. And since the crop factors on DSLRs vary from 1:1 to 2:1, Ron's sweeping generalisations
were NOT very reasonable for average use.

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cmyk

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