On Thursday, 1 October 2015 16:10:01 UTC+1, NY wrote:
"whisky-dave" wrote in message
...
How certain are you that "depth of focus mark" is the correct term for
the
"underground symbol" mark?

only 99.48567892%

In camera manuals it's described as "focal
plane". Depth of focus (like depth of field) refers to a *range* of
distances - either side of the focal plane (in the case of depth of
focus)



Yep as I said.

http://petapixel.com/2012/06/01/ever...-camera-means/

Actually that page describes the point as the focal plane or film plane mark
and doesn't use the term "depth of focus".


The only time when the precise position of the tripod mount is critical
(as
far as I am aware) is when taking multiple overlapping photos eg for a
panorama.

No don't agree there.

would yuo really mount this lens on yuor camera and use your camera tripod
socket.
http://www.amazon.co.uk/650-2600mm-D... _SR160%2C160_

There's a reason why long lenese come with tripod sockets even my M3 to
EOS converter as a tripod socket.

I agree that it would be horrendously out of balance. It's one hell of a
lens. I wouldn't like to hand-hold something 2.8 kg in weight and as long as
that - no smutty comments :-)

dam I had a long list of those :-)


And with a 2x converter - with a 5200 mm lens

I used a 400mm with a 2X and a 3X converter

you could probably almost have seen Neil Armstrong doing his "great leap"
;-) If 50 mm is regarded as 1:1 magnification.



then this thing is over 200x

I make it 104X with a FF sensor 166X with my EOS M3.
I'm thinking of buying one, but also considerign I:d be better off with a telescope.
I got some reasonable moon pics with my 70-300mm

magnification. Camera shake, thermal currents over long distances and
optical quality might be a problem.

yes that's why it's in a light colour too.


I did say "precise" and I meant it as opposed to approximate. For balance
you mount a heavy lens as close to the centre of gravity of the lens+camera
unit, but the exact position isn't too critical.

dependiong on the lens of course. I doubt many people even pros choose a camera based on where the tripod mount is.



Where it becomes critical, so I am told, is when taking several photographs
to join together. And then you'd mount the camera to rotate about its
sensor/film point. The two different uses wouldn't really come into conflict
as you are unlikely to use a 2600 mm lens to take separate images of a
panorama!

True and with modern software I don't think it's that importent.
I've done basic panos of 3 pics or so hand held.



to move the
rotation point accurately to the position of the sensor if the camera's
own
tripod bush isn't in the right place,

what do you mean by isn;t in teh right place why would a camera maker not
put the tripod mount not oin the right place ?

As I said earlier it seems from a very quick sample of cameras I can lay my
hands on that DSLRs (and almost certainly film SLRs) do put the tripod mount
at that point (Nikon D90, Canon 10D), but compact cameras don't always
(Canon SX260). But that's a very limited sample. I can't find my older G9
compact to see where its mount is.

pdreview might have the info too.
I have a canon G10