[photo] I'm getting a bit clever for my boots

* Russell D. wrote :
Mr.T wrote:
"Troy Piggins" wrote in message
...
A dewdrop refraction AND an insect macro in the same shot?
Surely that's not possible, unless you are AWESOME!

http://piggo.com/~troy/photos.php?al...2008_07_19/img
_8742.jpg

Pity the large drop looks pasted on,

I'm curious, Mr. T, why you thing the drop looks pasted on? If you look
closely, one of the "hairs" of the grass is disturbing the surface
tension of the drop as is hangs there. That would be hard to "fake" in
PS I would think.

Another really fun shot, Troy. Good work.

Thanks mate

--
Troy Piggins
I always appreciate critique.

Troy Piggins wrote:

pic

Nice photo :-)

* Colin.D wrote :
Troy Piggins wrote:
* Chris Malcolm wrote :
Troy Piggins wrote:

I'm very impressed, especially by the effective depth of field which
drops off slwoly enough to keep a lot of interesting detail past
sharpes focus. Was that achieved by a small aperture?
Thanks mate. f/9 was the aperture. DOF is razor thin with macro
shots, even at smaller apertures. f/2.8 is probably a millimetre
or so before you get instant bokeh. But it's a balance, because
if you stop down to f/16 or more the image becomes softer due to
diffraction softening, an effect which has less impact at further
distances but really is consequential at macro distances.

Is that F/9 set by using the Av setting on the camera? I would think
that the effective aperture would be smaller, due to the extension tubes
carrying the lens further from the sensor. It could be nearer F/13 or
even F/16 if the tubes are long enough.

As a rough example, if you have 36mm of tube with a 35mm FL lens on the
front, your effective aperture is two stops smaller than the selected
aperture, so F/9 would become F/18 or thereabouts.

It always gets you one way or t'other!

G'day Colin. I don't use Av, I shoot full Manual. But I get
what you're saying. f/9 is what I set the camera at, it's not
effective aperture. I've read about those effects you're talking
about, but try not to think about it too much. I just know that
if I'm shooting bare lens (100mm) and up to 1:1, I keep the
aperture at f/11 or wider. When I add the tubes (68mm) to shoot
up to 2:1, I open up to around f/9 or so. Just from my (limited)
experience and what I've read.

I'd be interested to learn more about these effects. Possibly
even formulae for working it out.

I believe it's rather simple math: add the extension tube length to the
focal length when calculating f/stop

f/stop = focal length / diameter of front element (at infinity)

given a 90mm f/2.8 lens... with 50mm extension
90/2.8 = 32mm front element (effective part at 90mm infinity)
90+50 = 140mm/32 = f/4.4

given a 90mm lens at f/9... with 50mm extension
90/9 = 10mm front element (effective part at 90mm infinity)
90+50 = 140mm/10 = f/14

However, modern macro lenses shorten the focal length when close
focusing and the stopped down max aperture is an indication of that effect:

My 105 macro goes from f/2.8 to f/4.8 when focusing close from infinity
so...

given a 105mm f/2.8 lens...
105/2.8 = 37.5mm front element (effective part at 105mm infinity)

focused close it's an x_mm f/4.8 lens...
4.8*37.5 = 180mm focal length at 1:1

Well crap, my math has obviously failed

:-(

I measure the front element at about 70mm, so:

4.8*70 = 336mm at 1:1

yep, I'm lost... sorry :-)


Just this morning I came across formulae for depth of field and
exposure where they're affected by higher magnifications than
1:1. Haven't tested them or put them into practice yet.

Thanks for the comments.



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

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* Paul Furman wrote :
Troy Piggins wrote:

pic

Nice photo :-)

Thanks mate

[---=| Quote block shrinked by t-prot: 27 lines snipped |=---]
what you're saying. f/9 is what I set the camera at, it's not
effective aperture. I've read about those effects you're talking
about, but try not to think about it too much. I just know that
if I'm shooting bare lens (100mm) and up to 1:1, I keep the
aperture at f/11 or wider. When I add the tubes (68mm) to shoot
up to 2:1, I open up to around f/9 or so. Just from my (limited)
experience and what I've read.

I'd be interested to learn more about these effects. Possibly
even formulae for working it out.

I believe it's rather simple math: add the extension tube length to the
focal length when calculating f/stop

f/stop = focal length / diameter of front element (at infinity)

given a 90mm f/2.8 lens... with 50mm extension
90/2.8 = 32mm front element (effective part at 90mm infinity)
90+50 = 140mm/32 = f/4.4

given a 90mm lens at f/9... with 50mm extension
90/9 = 10mm front element (effective part at 90mm infinity)
90+50 = 140mm/10 = f/14

Right-O - that makes sense I guess.

However, modern macro lenses shorten the focal length when close
focusing and the stopped down max aperture is an indication of that effect:

My 105 macro goes from f/2.8 to f/4.8 when focusing close from infinity
so...

given a 105mm f/2.8 lens...
105/2.8 = 37.5mm front element (effective part at 105mm infinity)

focused close it's an x_mm f/4.8 lens...
4.8*37.5 = 180mm focal length at 1:1

Well crap, my math has obviously failed

:-(

LOL - I was with you til there...

I measure the front element at about 70mm, so:

4.8*70 = 336mm at 1:1

yep, I'm lost... sorry :-)

Hahaha. Thanks for trying.

--
Troy Piggins
I always appreciate critique.

Troy Piggins wrote:
* Paul Furman wrote :
Troy Piggins wrote:

f/9 is what I set the camera at, it's not
effective aperture. I've read about those effects you're talking
about, but try not to think about it too much. I just know that
if I'm shooting bare lens (100mm) and up to 1:1, I keep the
aperture at f/11 or wider. When I add the tubes (68mm) to shoot
up to 2:1, I open up to around f/9 or so. Just from my (limited)
experience and what I've read.

I'd be interested to learn more about these effects. Possibly
even formulae for working it out.

I believe it's rather simple math: add the extension tube length to the
focal length when calculating f/stop

f/stop = focal length / diameter of front element (at infinity)

given a 90mm f/2.8 lens... with 50mm extension
90/2.8 = 32mm front element (effective part at 90mm infinity)
90+50 = 140mm/32 = f/4.4

given a 90mm lens at f/9... with 50mm extension
90/9 = 10mm front element (effective part at 90mm infinity)
90+50 = 140mm/10 = f/14

Right-O - that makes sense I guess.

However, modern macro lenses shorten the focal length when close
focusing and the stopped down max aperture is an indication of that effect:

My 105 macro goes from f/2.8 to f/4.8 when focusing close from infinity
so...

given a 105mm f/2.8 lens...
105/2.8 = 37.5mm front element (effective part at 105mm infinity)

focused close it's an x_mm f/4.8 lens...
4.8*37.5 = 180mm focal length at 1:1

Well crap, my math has obviously failed

:-(

Hahaha. Thanks for trying.

Obviously some complex design stuff has messed up the possibility of
simple math. If you chose to leave the lens focused at infinity & use a
bellows to get close focus, the math should work but I think the modern
designs shift things around muchly :-) There probably is some benefit
lost by not moving those internal elements and relying on extension only
by it's worth noting that even with a simple fixed group of lens
elements, the stated focal length is only valid at infinity and focusing
closer makes the *actual* focal length longer in exactly the same way as
adding extension tubes so that 180mm in the first guess is probably
right (if you kept focused to infinity).

Really extreme macros are done with rather short focal lengths on very
long extensions... kind of a contradiction if my theory is correct. The
closer you focus, the smaller the bit of central glass is used. Nobody
uses f/1.4 microscope lenses with 77mm filter threads.

Anyways it looks like you were working in the sweet spot for that setup.

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

all google groups messages filtered due to spam