Apertures for Len Stacking?

I'm shooting studio macro with a manual aperture Pentax 50mm f/1.7 reverse
mounted on a Canon EF-S 55-250mm at 250. I'm going to do some testing to
find the best combinations of apertures for maximum DOF and IQ without
obvious diffraction. Where would you start with the apertures? I want to
hear something like, use the same aperture on both lenses, tight on the
primary and wide on the reversed, the other way around... what has worked
for you with that kind of setup?

I don't have a problem with stopping down the reversed lens - I have enough
light on the subject.

Wilba wrote:
I'm shooting studio macro with a manual aperture Pentax 50mm f/1.7
reverse mounted on a Canon EF-S 55-250mm at 250. I'm going to do some
testing to find the best combinations of apertures for maximum DOF and
IQ without obvious diffraction. Where would you start with the
apertures? I want to hear something like, use the same aperture on both
lenses, tight on the primary and wide on the reversed, the other way
around... what has worked for you with that kind of setup?

I don't have a problem with stopping down the reversed lens - I have
enough light on the subject.

Stop down the front 50mm lens. Here's a discussion of almost the same
setup you describe:
http://www.photomacrography.net/foru...pic.php?t=8336
Figure out the best aperture by testing.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

Paul Furman wrote:
Wilba wrote:

I'm shooting studio macro with a manual aperture Pentax 50mm f/1.7
reverse mounted on a Canon EF-S 55-250mm at 250. I'm going to do some
testing to find the best combinations of apertures for maximum DOF and IQ
without obvious diffraction. Where would you start with the apertures? I
want to hear something like, use the same aperture on both lenses, tight
on the primary and wide on the reversed, the other way around... what has
worked for you with that kind of setup?

I don't have a problem with stopping down the reversed lens - I have
enough light on the subject.

Stop down the front 50mm lens. Here's a discussion of almost the same
setup you describe:
http://www.photomacrography.net/foru...pic.php?t=8336

Thanks a bunch, just what I was looking for.

Figure out the best aperture by testing.

Now I have a strategy for a test - set the primary aperture to its widest
and find the optimal aperture on the reversed lens. Then I'll see if
stopping down the primary aperture makes a difference for that reversed
aperture.

Wilba wrote:
Paul Furman wrote:
Wilba wrote:

I'm shooting studio macro with a manual aperture Pentax 50mm f/1.7
reverse mounted on a Canon EF-S 55-250mm at 250. I'm going to do some
testing to find the best combinations of apertures for maximum DOF
and IQ without obvious diffraction. Where would you start with the
apertures? I want to hear something like, use the same aperture on
both lenses, tight on the primary and wide on the reversed, the other
way around... what has worked for you with that kind of setup?

I don't have a problem with stopping down the reversed lens - I have
enough light on the subject.

Stop down the front 50mm lens. Here's a discussion of almost the same
setup you describe:
http://www.photomacrography.net/foru...pic.php?t=8336

Thanks a bunch, just what I was looking for.

Figure out the best aperture by testing.

Now I have a strategy for a test - set the primary aperture to its
widest and find the optimal aperture on the reversed lens. Then I'll see
if stopping down the primary aperture makes a difference for that
reversed aperture.

As a starting point, effective aperture at about 4x like that will be...
(assuming the zoom is f/5.6 on the long end) ...

f-number (magnification +1)
5.6 (4+1) = f/28

But there's plenty of variables & things to mess up that math.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

Paul Furman wrote:
Wilba wrote:
Paul Furman wrote:
Wilba wrote:

I'm shooting studio macro with a manual aperture Pentax 50mm f/1.7
reverse mounted on a Canon EF-S 55-250mm at 250. I'm going to do some
testing to find the best combinations of apertures for maximum DOF and
IQ without obvious diffraction. Where would you start with the
apertures? I want to hear something like, use the same aperture on both
lenses, tight on the primary and wide on the reversed, the other way
around... what has worked for you with that kind of setup?

I don't have a problem with stopping down the reversed lens - I have
enough light on the subject.

Stop down the front 50mm lens. Here's a discussion of almost the same
setup you describe:
http://www.photomacrography.net/foru...pic.php?t=8336

Thanks a bunch, just what I was looking for.

Figure out the best aperture by testing.

Now I have a strategy for a test - set the primary aperture to its widest
and find the optimal aperture on the reversed lens. Then I'll see if
stopping down the primary aperture makes a difference for that reversed
aperture.

As a starting point, effective aperture at about 4x like that will be...
(assuming the zoom is f/5.6 on the long end) ...

f-number (magnification +1)
5.6 (4+1) = f/28

But there's plenty of variables & things to mess up that math.

I'm doing this to do photos, not maths. :-D

F/8 on the 250 and f/9.5 on the 50 gave the best results today.