Infinity focus & extension tubes

[Dr Croubie]

I've seen some debate as to whether or not
a 12mm extension tube could be used on a very long telephoto lens and
still retain infinity focus, but I've never seen proof of it working.

and
just to spam this thread with another reply: i've got a 250mm f/3.5
soviet MF prime, and two 2x teleconverters (making 1000mm f/14). if i
could find a way to mount it on a tripod i'd give it a go when the sun
comes out...

[Sean Setters]

and just to spam this thread with another reply: i've got a 250mm f/3.5 soviet MF prime, and two 2x teleconverters (making 1000mm f/14). if i could find a way to mount it on a tripod i'd give it a go when the sun comes out...

LOL.....go for it.

[mmodica]

Thanks for all the replies everyone. Focusing off to the hyperfocal would be fine, but I calculated that the hyperfocal at 135mm with f/5.6 would be ~557 ft which is pretty close to infinity. Even stopping down to f/11 (which I almost never do) only brings the hyperfocal back to 279ft.


Judging by the distance scale on the 28-135mm it looks like at the shorter focal lengths it can focus past infinity but again I do like being able to zoom to 135mm. I guess I

[Dr Croubie]

I don't know what was worse:


the IQ i got from 2x 2x teleconverters that seem to love purple, mounted on an already not-the-best lens,


or the thought of my neighbours ringing the cops because i was
pointing a big, black, bazooka-looking thing in the vicinity of the city
centre:


[img]/photography_gear1/resized-image.ashx/__size/1200x0/__key/CommunityServer-Discussions-Components-Files/8/7608.P7112335s.JPG[/img]


.


at any rate, the farthest focussing i got was about 3-500m, even at
f/5.6 * 4 (f/21.6) my DOF was only a few meters, the branches behind
were OOF. (and the weird things at the top of the photo were a
palm-thing across the road from me, maybe 30-50m away.) the branch at
lower left seems to be the best in focus, best you can get with that
setup at ISO3200 on a 7D at any rate.


[img]/photography_gear1/resized-image.ashx/__size/1200x0/__key/CommunityServer-Discussions-Components-Files/8/7416.IMG_5F00_5958s.JPG[/img]






your mileage may vary, anyone got an 800mmL or a 1200mmL? (there's one on ebay now, only US$80000, who wants to buy it to test?)

[neuroanatomist]

@mmodica - Welcome to the TDP Forums! Nice to see another 'local' (I'm in the Boston area).


To continue the threadjack a bit:

your mileage may vary, anyone got an 800mm

No, but on an outing a couple of months ago (with Bill W.), I tried a 2x II Extender with my 100-400mm. It was a staring contest between a great horned owlet and a grackle. The owlet won, eventually (after a few dive-bombs by the aggressive grackle).


Focusing at 1280mm FF-equivalent (800mm on the 7D) was tough, even on a tripod with IS turned on (and with no IS, it would have been very, very tough!). I think the results of the 800mm combo turned out better than the equivalent shot at 400mm (from the same position) with the FoV cropped to match the 800mm shot:


[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/100_2D00_400_2B00_2x.jpg[/img]

[HDNitehawk]

@mmodica - Welcome to the TDP Forums! Nice to see another 'local' (I'm in the Boston area).


To continue the threadjack a bit:

your mileage may vary, anyone got an 800mm

No, but on an outing a couple of months ago (with Bill W.), I tried a 2x II Extender with my 100-400mm. It was a staring contest between a great horned owlet and a grackle. The owlet won, eventually (after a few dive-bombs by the aggressive grackle).


Focusing at 1280mm FF-equivalent (800mm on the 7D) was tough, even on a tripod with IS turned on (and with no IS, it would have been very, very tough!). I think the results of the 800mm combo turned out better than the equivalent shot at 400mm (from the same position) with the FoV cropped to match the 800mm shot:


[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/100_2D00_400_2B00_2x.jpg[/img]
<div style="CLEAR: both"]</div>

John


Thats a really cool shot. Did the 500mm get bumped up a notch or two on your wish list after that one?


Rick

[mmodica]

Interesting stuff guys, thanks for sharing (and for the welcome)!