depth of field with different lenses

On Wed, 9 Mar 2011 12:13:09 -0800, Savageduck
wrote:

On 2011-03-09 10:39:15 -0800, Eric Stevens said:

On Tue, 15 Dec 2009 20:25:18 -0600, Allen
wrote:

Troy Piggins wrote:
* Wally wrote :
On Wed, 16 Dec 2009 08:30:30 +1000, Troy Piggins
wrote:

[---=| Quote block shrinked by t-prot: 14 lines snipped |=---]
of view as the 150mm lens shot:
http://piggo.com/~troy/images/usenet...-f2_8-crop.jpg

With the wider focal length lens, same aperture, same camera,
same focus distance, there is more stuff acceptably in focus.
First of all, good for you for doing tests. You will learn real
things. Experiments beat theory.

Secondly, you are right, shooting with a wide angle lens and then
cropping to the same image size will give you much better DOF.

But thirdly, if you move in with the wide angle to get the same image
size, then the DOF will be the same.

Except that it might not be -- I suspect the latter case will show the
long lens to give better DOF. That's because the exit pupil is
usually smaller than expected for tele lenses. Look at the front of
the lens, then at the back. Do the apertures look the same size? It
will probably look smaller from the back, and that should give better
DOF.

The perspective is different too. That's not what I was trying
to test. As to whether the DoF will be the same, don't know and
don't care at the moment. I was trying to illustrate a point
raised in another thread.

I know if you move closer, ie reduce focus distance, the DoF
narrows as well. So it makes sense that at some point if you
take a shot with a longer lens, and another shot closer to the
subject with the same aperture, you could end up with
similar/same DoF. But the perspectives will be different, and
the field of view may or may not be the same.

In 1941, when I was 12 years old, I bought a book titled "How to Make
Good Pictures" from Kodak for something like 50 cents. (I believe this
edition was from 1939 or 1940.) It was a wonderful introduction to
photography. Many of the questions I see here (basic lighting, posing,
composition, optics, depth of field, shutter speeds, filters and
such--and an intro to darkroom work, useless now) are answered in that
70 year old, approximately 150 page book. Looking in bookstores, I don't
see anything like that book. What I see now weigh as much as a 4x5
Graflex (a conparison from the time when that book was published) and
difficult to find answers to your questions. I practically wore the ink
off the pages in a year. We need a digital-age equivalent.
Allen

I agree. My introduction was via the 'Ilford Encyclopaedia of
Photography'. I don't know what happened to my copy but I've been
fruitlessly hunting for an eqivalent for the last several years.

Regards,

Eric Stevens


A little searching shows that the 'Ilford Encyclopaedia of Photography'
first published in 1890 by Britannica Works Co. became the "Ilford
Manual of photography".

A check with Amazon shows it somewhat available;

http://www.amazon.com/Ilford-Manual-...9700789&sr=1-1

or
http://thurly.net/111a

They show other used editions dating from 1897;

http://www.amazon.com/s/ref=nb_sb_ss...of+photography

or
http://thurly.net/1119

That looks like the one.

Regards,

Eric Stevens