On 7/6/2012 10:52 PM, John Celio wrote:
So I have this setup for shooting seriously close-up macro:
https://picasaweb.google.com/lh/photo/CIUtr5fsiR0rzShfFjE08NMTjNZETYmyPJy0liipFm0?feat=directlink
That is: Camera / helicoid tube at 49mm / bellows at 137mm (approx)/
12mm tube / 20mm tube / 36mm tube / generic reverse mount ring / D-FA
100mm macro at 1:1
I've been meaning to share this for a while, because the last time I
tried using it in this configuration (sans rear cap on the lens, of
course), I was unable to focus on anything. I had a little flower
practically pressed against the glass at the end there but had to pull
the lens' focus back about halfway before I could actually focus on
it.
So I'm hoping you guys can help me figure a couple things out:
1. Is it possible to have a lens so far away from the sensor plane
that focus can't be achieved?
2. What's the macro ratio of this setup as it is in the picture?
3. Does it make a difference if I have the lens reverse-mounted like
this rather than mounted normally on the last extension tube?
4. Would it be ridiculous or just silly to attempt to add more
extension in the future?
John
That is basically the same setup that I use for my snow crystal shots,
except I use a 50mm lens reverse mounted. In fact, it is so simlar I
just now pulled it out of the closet, set it up and put my D-FA 100mm
macro on it. I have 300mm of extension (tubes and bellows) with the lens
reverse mounted at the end.
Your focusing problem lies in how how the D-FA 100 close focuses. I had
no problem getting a shot in focus when the lens was set to infinity,
and actually had ample working room. As I adjusted the lens's focusing
mechanism I quickly was unable to get anything into focus. Obviously,
something about the internal focusing on the D-FA causes a problem with
it reverse mounted.
Focusing on a ruler, with the D-FA 100 at infinity, and using a full
frame 35mm film camera (also pulled from the closet), I saw 8 to 9 mm in
the view finder. SO I reckon it to be about 4x life sized. With the 50mm
I routinely use on this setup, the finder on the full frame camera shows
about 4 mm, so about 8x.
If you really want to get extreme get a short and fast lens and use it
on all that extension. A 24mm on 300mm of extension would result in 16x
or so magnification. Set the lens to infinity or use one that does not
use internal focusing.
Regarding protecting the delicate rear element of the lens - put a short
extension tube on the rear lens mount. It will serve as a hood and also
offer some protection to the rear element. To help with focusing - set
up your rig in a dark place. Put a bright flashlight on the finder
(where your eye would go). It will project a little rectangle of light
that you can use to align your subject and get a sense of focusing
distance with (when the rectangle is sharp, you are in focus.)
Have fun -
Mark
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