An ISO Quality question

In article coh.net,
Philip Homburg wrote:
In article ,
DoN. Nichols wrote:
Not a consideration on the Cannon, but my Nikon D70 has a
minimum ISO of 200, and this prevents me from shooting at the highest
magnification range of the old 200mm Medical Nikkor (with the built-in
ring flash). It does the exposure calculation based on an ISO (actually
marked as ASA) setting ring, and a magnification ratio ring, resulting
in setting of the aperture ring.

What may work is to set the shutter speed sufficiently high that only part
of the flash output is captured . This works on the D1 (though I didn't try
it with a medical Nikkor), and I think that it is also supposed to work with
a D70.




According to what I'm reading my new 420EX flash on my 300D can sync
at "any" speed if a switch on the flash is set to "FP". It does
this by doing a 50KHz (I think) strobe effect and the power is
reduced as a byproduct.

It's recommended for fill flash in bright sun. I haven't played with
it.


--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.

In article , Al Dykes wrote:
In article coh.net,
Philip Homburg wrote:
In article ,
DoN. Nichols wrote:
Not a consideration on the Cannon, but my Nikon D70 has a
minimum ISO of 200, and this prevents me from shooting at the highest
magnification range of the old 200mm Medical Nikkor (with the built-in
ring flash). It does the exposure calculation based on an ISO (actually
marked as ASA) setting ring, and a magnification ratio ring, resulting
in setting of the aperture ring.

What may work is to set the shutter speed sufficiently high that only part
of the flash output is captured . This works on the D1 (though I didn't try
it with a medical Nikkor), and I think that it is also supposed to work with
a D70.




According to what I'm reading my new 420EX flash on my 300D can sync
at "any" speed if a switch on the flash is set to "FP". It does
this by doing a 50KHz (I think) strobe effect and the power is
reduced as a byproduct.

It's recommended for fill flash in bright sun. I haven't played with
it.

Intersting -- though how it can be applied to the situation
above, a Nikon D70 camera body, and a truly antique Medical Nikkor with
a built-in ring flash (old enough so the only semiconductor in it is
the rectifier in the HV power supply.)

If this were a modern enough flash so it could be set to reduced
output, the whole problem would go away. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

In message ,
(Al Dykes) wrote:

According to what I'm reading my new 420EX flash on my 300D can sync
at "any" speed if a switch on the flash is set to "FP". It does
this by doing a 50KHz (I think) strobe effect and the power is
reduced as a byproduct.

It's recommended for fill flash in bright sun. I haven't played with
it.

It's not really like flash at all; it's like an ambient light that is
strobing invisibly, unless something moves quickly, in which case you
will get non-contiguous sub-exposures.

I think of it as extra light, not "flash" per se. On your 300D, the
flash will be up to 4x as strong, and/or up to 1/40 the duration at
1/200 than at 1/250. In other words, at 1/200, you could use a 600mm
lens, hand-held, and the flash part of the exposure will be sharp, and
punctuate the image, even if the ambient is slightly blurry. At 1/250,
when fp kicks in, you will have a blurry image. I used to leave my
550EX set to fp mode, with the safety of knowing that it disabled if the
10D is set to 1/200 or slower, or 1/250 on the 20D, but what wound up
happening is that I'd use faster shutter speeds and get blurrier images,
so I now only enable it on a per-need basis.
--


John P Sheehy

On 10 Aug 2005 23:49:31 -0400, (DoN. Nichols)
wrote:


The lens is capable of going down to a 3X magnification ratio,
but the closest that I can get at present is a 2/3X magnification ratio
because of the exposure situation.

Why not try to diffuse and/or partially block the flash to control the
light. I have no idea what your lens flash looks like but I have an
old Viviitar ring light and I can tape a thin paper ring on it to cut
the output in half.

Dave
East Englewood
---------------------
The proof is in the print.

In article ,
wrote:
On 10 Aug 2005 23:49:31 -0400, (DoN. Nichols)
wrote:


The lens is capable of going down to a 3X magnification ratio,
but the closest that I can get at present is a 2/3X magnification ratio
because of the exposure situation.

Why not try to diffuse and/or partially block the flash to control the
light. I have no idea what your lens flash looks like but I have an
old Viviitar ring light and I can tape a thin paper ring on it to cut
the output in half.

The ring flash is built into the lens body. If you want some
excellent photos and drawings, take a look at the following recently
closed eBay auction:

Auction Number: 7536353068

Full URL: http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7536353068

I have already received such a suggestion, and essentially a
ring cut from a neutral density filter gel would work nicely for the
purpose.

I also, while examining an older separate ring flash which I had
stored away discovered that it had a rheostat between the lamp and the
capacitor, which adjusts the output through perhaps a 4:1 ratio (I'm not
sure, as I don't have a flash meter.) At the very bottom of the range,
the flash will not trigger -- but a 4:1 ratio should be sufficient for
my purposes. And that could be put in a cord between the power supply
and the flash head.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---