Re: [Leica] Re: DOF

[Mark Rabiner <mark@rabiner.cncoffice.com>]

John Collier wrote:
> 
> Michael.
> 
> Please look in your library for books such as Ansel Adams' "The Camera" and
> other similar books. You can read it there for yourself.
> 
> DOF is determined by just two factors: final image size and relative
> aperture used.
> 
> Perspective is a function of viewpoint only.
> 
> Lens choice does not enter in at all. Take a picture with the subject
> filling the frame with your 90 and 35 using the same aperture (you will have
> to move closer with the 35). Print to the same size and you will get the
> same depth of field. Now take a picture of any scene with your 90 and 35
> without changing position. Print the 90 full frame and crop the 35 to match,
> identical perspective.
> 
> Ansel has his answers illustrated and will be much easier to comprehend than
> anything I can cram into my cable line.
> 
> John Collier
> 
Yes the best source for this practical info imo is Ansel.
There is no need to read books explaining Ansel he explains himself better than
anyone could.
But on this issue I dare to differ with the numbers and with i suppose therefore Ansel.
If you fill the top to bottom of the chair with a 28mm it should give you just
as much front to back dof as when you pull way back across the street and fill
the chair top to bottom with a 90mm lens.
But it doesn't'. 
Just doesn't seem to ever work that way. 
A wider angle lens will always seem to give you more.
Despite what the numbers seem to say.
Why would the numbers be wrong I'd like to know but they are in my and many
otherses practical experience.
mark rabiner