600mm telephoto with extension tube – some figures.
Posted: Fri Nov 10, 2017 1:55 pm
Hi everyone,
I visited one of our local offshore bird reserves today with my 600mm telephoto to capture some images of our smallest NZ bird - the Rifleman (weighing in at a mere 6.0 grams).
I used a single 36mm extension tube with the lens to see what benefit could be gained (mainly in terms of shortening its minimum focus distance).
The rifleman bird I had in mind tends to use a favourite perching twig in the forest and is thus very predictable in terms of location and distance from the path. The perch is well inside the normal focus range of the 600mm, but I wanted to test the effect of adding the 36mm ext. tube on lens performance.
I noted the following details:
Infinity focus is now approx. at 50 ft (15m)
Closest focus is now at approx. at 10 ft (3m) instead of 16.4 ft (5m)
E.J and Dick Ludwig are right about minimal light loss, as the camera display tells me the lens still goes as wide as f4 so no change there. (Have you noticed how an f2.8 macro suddenly becomes an f5.6 max aperture when you add extension tubes?)
Chris Ross is right, photographing the same branch with and without the 36mm extension tube reveals a slight magnification (measured on the computer screen) of 110.5% with the extension tube as might be expected. (So a 600mm lens becomes 662mm)
I have heavily cropped the photo attached, but did not see any bad vignetting on the original RAW file (although the forest was pretty dark on this occasion making it hard to tell). Exposure was f8 at 1/60 ISO 200, with TTL BL flash set at -3 stops underexposure, later recovered in ACR.
Interestingly, the combination seems to be spot on focus wise (see photo to see if you agree)
Previously, without the ext. tube, focus had been pretty much spot on/very slightly front focus (with the original fine adjustments for this camera body).
I have two fine adjustment settings stored on this D810 camera body (one for the 600mm alone and a second for the 600 plus a 1.7x TC).
A suggestion was made by E.J. to store a third (600 + Ex. Tube).
Question – If I do, how does the camera body KNOW whether it is the 600mm alone or the 600 + ext. tube? As the Kenko ext. tubes do not contain any “intelligent chips” announcing its presence to the camera (presumably)?
Taking Joe Smith’s advice, I resisted the temptation to go the whole 9 yards and slap the full set of tubes on, as the camera/flash combo weighs nearly 2kg and I had visions of the Kenko tubes breaking and sending the body/flash combo crashing earthwards.
Hope this report isn’t too wordy and you find it interesting!
John Sibley
I visited one of our local offshore bird reserves today with my 600mm telephoto to capture some images of our smallest NZ bird - the Rifleman (weighing in at a mere 6.0 grams).
I used a single 36mm extension tube with the lens to see what benefit could be gained (mainly in terms of shortening its minimum focus distance).
The rifleman bird I had in mind tends to use a favourite perching twig in the forest and is thus very predictable in terms of location and distance from the path. The perch is well inside the normal focus range of the 600mm, but I wanted to test the effect of adding the 36mm ext. tube on lens performance.
I noted the following details:
Infinity focus is now approx. at 50 ft (15m)
Closest focus is now at approx. at 10 ft (3m) instead of 16.4 ft (5m)
E.J and Dick Ludwig are right about minimal light loss, as the camera display tells me the lens still goes as wide as f4 so no change there. (Have you noticed how an f2.8 macro suddenly becomes an f5.6 max aperture when you add extension tubes?)
Chris Ross is right, photographing the same branch with and without the 36mm extension tube reveals a slight magnification (measured on the computer screen) of 110.5% with the extension tube as might be expected. (So a 600mm lens becomes 662mm)
I have heavily cropped the photo attached, but did not see any bad vignetting on the original RAW file (although the forest was pretty dark on this occasion making it hard to tell). Exposure was f8 at 1/60 ISO 200, with TTL BL flash set at -3 stops underexposure, later recovered in ACR.
Interestingly, the combination seems to be spot on focus wise (see photo to see if you agree)
Previously, without the ext. tube, focus had been pretty much spot on/very slightly front focus (with the original fine adjustments for this camera body).
I have two fine adjustment settings stored on this D810 camera body (one for the 600mm alone and a second for the 600 plus a 1.7x TC).
A suggestion was made by E.J. to store a third (600 + Ex. Tube).
Question – If I do, how does the camera body KNOW whether it is the 600mm alone or the 600 + ext. tube? As the Kenko ext. tubes do not contain any “intelligent chips” announcing its presence to the camera (presumably)?
Taking Joe Smith’s advice, I resisted the temptation to go the whole 9 yards and slap the full set of tubes on, as the camera/flash combo weighs nearly 2kg and I had visions of the Kenko tubes breaking and sending the body/flash combo crashing earthwards.
Hope this report isn’t too wordy and you find it interesting!
John Sibley