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Dan Schwartz

Member Since 15 Oct 2007
Offline Last Active Apr 22 2009 09:23 PM
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Posts I've Made

In Topic: Medium format ergonomics

20 November 2007 - 08:29 PM

Craig, I don't appreciate you taking this thread off topic with your insults.

Do me, and all of us, a favor, please: Change your personal settings to ignore my posts.

In Topic: Manual Focus Nikon 16mm fisheye

20 November 2007 - 08:09 PM

Gerard, the article you cite below has some bad info on hyperfocal distance: The strict definition is the closest distance remaining in focus while infinity is also in focus. The last definition (from 2000) is correct when one of the two distances is at infinity.

I normally don't like to quote Wikipedia, at least until I look at the references and the discussion. That being said, the Hyperfocal Distance article looks pretty good.

For a more thorough description, see Harold Merklinger's book The INs and OUTs of Focus, now available in PDF.

MF might be better, because you could use the DOF to your advantage by setting the hyperfocal distance.
http://www.dofmaster...hyperfocal.html


PS: I shoot large format sometimes, bending the bellows into a pretzel! :)

In Topic: Medium format ergonomics

20 November 2007 - 07:45 PM

Note: For those of you who want to block my posts, here are the instructions. :)

Already own 3, 4 & 5; but more...

3) Get digital point and shoot for about 20-40 dives
4) Buy digital SLR
5) If sometime down the road you need a medium format for whatever random reason at least you will know how to dive without killing the ocean or yourself


While looking again at the Lens & Repro rental counter display of three Nikonos V rangefinder bodies occupying less space than the Nikonos RS sitting next to it... Then looking at the Fuji GA645 (6x45 rangefinder) sitting in my camera bag, something occured to me:

The problem with taking medium format underwater is not the size of the film or the larger CCD: It's the larger lenses caused by the longer lens-to-film distance to clear the mirror box in an SLR.

A good explanation is found written by Phil Askey on the Leica M8 on DPReview.com:

Solving the corner vignetting problem

Because a rangefinder camera doesn't have a mirror box [it] doesn't need to use retrofocus lenses, meaning they sit much closer to the film (or in this case the sensor). The problem with this comes with wide angle lenses (which are pretty much the main staple of the rangefinder camera). [Emphasis added: DLS] Towards the corner of the frame the angle of incidence of light coming from the rear of the lens is so severely off-perpendicular that they would not pass equally through the microlenses above the sensor leading to fairly strong vignetting. Even a modest wide angle lens at this kind of distance could produce a difference of a stop or two between the center of the frame and the edges using a standard CCD sensor.

Leica, obviously keen to solve this problem, took a three pronged approach with the M8:
(Cut: Balance in article)


OK, since a picture is worth a thousand words, which camera in this picture would you .NOT. want to build a housing for, or wrangle with in hostile conditions (such as underwater):

Posted Image

Posted Image

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This shot of a next to a 6x6 SLR and 35mm SLR shows the issue with the mirror box depth and effect on lens retrofocus:
Posted Image


Incidentally, this Cambo with a 24mm lens is a camera that would be easy to build a housing for, using the same 39 MP back Troy has mounted to his Hassy H3D (16mm focal length with FX, 11mm with DX equivalents).
Posted Image

I'm going to bed now; but I'm sure the engineers at the housing manufacturers are watching this thread for ideas.

EDIT: The Cambo above becomes a 39 megapixel medium format point & shoot if the digiback has live focus available on the LCD...

In Topic: Into a pool

20 November 2007 - 07:37 PM

The lighting on this shot you posted is superb!

I especially like the way the strobe reflected off the water onto the swimmer's cheek, chin and throat.

Also, the strobe froze everything nicely: No evidence of front or rear curtain sync.

In Topic: Pool/Model Photos

20 November 2007 - 07:30 PM

James,

I just discovered these shots tonight... Great work! :)

Your photos prove the point that there's more to underwater photography than just reef shots.