Re: [KOML] Depth of Field

[Clive Warren <Clive.Warren>]

At 11:08 am -0800 3/11/99, Tom Cogbill wrote:

>Returning to the Depth of Field Question on Koni-Omega Lenses...
>
>apparently there is some misunderstanding as to what I am talking
>about.  On my 90 mm K-O lens, if you pull out the lens hood at the end
>of the barrel, a scale is revealed which correlates f-stop settings with
>distances.  This is a depth-of-field scale which, to my knowledge, most
>lenses with a fixed focal length have.  But not, unfortunately, the 180
>mm lens (nor the 58 mm, though DOF is generally large on W-A lenses,
>which is evidently why there is no separate focusing mechanism for it.
>The scales on the focusing knob simply indicate focusing distance).   I
>was just wondering why these lenses have no DOF scales.
>
>Thanks much to George for the link to the K-O manual.  It is far more
>informative than the rather silly "manual" that accompanied the version
>I bought.  (My camera, incidentally, has some slight variations from
>what is described in the on-line manual.)  I note that it gives DOF
>tables for all the lenses, so I guess they expect you to memorize these
>if you  want that info for the lenses other than the 90.
>
>Incidentally, does anyone have the "close-focus" adapters, and if so,
>are they worth a damn?  I've heard extension tubes were made for the K-O
>models, but that hardly anyone bought them, suggesting they may be
>impractical or of too limited value.
>
>--Tom

Tom,

Yes it is a bit of a planning failure rather than design flaw.  Maybe the
cost of adding the scale to the larger lenses was just more than the
accountants could bear at the time ;-)

There is a DOF calculator available through the front page of the CoCam
website which will allow you to calculate DOF for many different formats
and any lens focal length.  The last update was to add a print button for
those too lazy to make more than one key press or mouse click :-)  I carry
a few of these print-outs tucked into the camera bags for various cameras.

The calculator is in the pop-up menu for "CoCam Photo Tools".  See sig.
file for URL.

Yes the close focus adapters do work, however they require the original
"series" filter ring to be in the lens - most of these have been removed to
allow use of contemporary 49mm fittings.  Given the hassle of setup it's
probably only worthwhile if the K-O is your main camera and you have no
other close-up alternatives with other camera equipment.

Using extension tubes requires the use of a groundglass back to focus.  I
have been looking for a set and the ground glass back for a couple of
years......

As to whether they are impractical - well the camera would no longer be
rapid and accurate focus portraiture would be a challenge in the same way
that it is for large format photographers who like to overflow the frame
with head shots.



All the best,

             Clive   http://www.cocam.co.uk
                     Photographic Services, Filters and Equipment, Infrared FAQ
                            http://clive.bel-epa.com
                            Adventures in Cyberspace - Digital Art and Photos