MFD question

I'm wanting to do some backyard birdin with the 400 5.6 lensand my distance is little less than 10 ft. Could someone tell me what the mfd would be if I added a 12mm ext tube?

Very little diffence with only 12mm on that long a lens.

In Lens Work III Canon only states the lens' level of magnification with their extension tubes attached. They don't state it in meters or feet. The 400mm alone is shown as having a MFD of 11.5 feet or 3.5 meters, and a max mag of 0.12X. With 12mm attached it's only changed to 0.16X mag. With 25mm attached it's 0.21X mag.

So if the lens alone has MFD of 138", just applying the percentage of differences in magnification, MFD with a 12mm tube should be about 103",and MFD with the 25mm tube should be approx. 80". So, yes, you should be able to get under 10' of working distance with either of the Canon extension tubes.

The link Wilt provided comes up with slightly different numbers. It shows the lens alone, with its reported 3.5 meter MFD, as closer to 0.13X magnification. It confirms about 0.16X with the 12mm extension, but closer to 0.20X with a 25mm. Substituting these figures into the calculations, MFD with 12mm should be about 112" (and farthest point of focus, 45 feet) and MFD with 25mm extension tube should be about 90" (and farthest point of focus under 21 feet). But, again, either one should work for 10 feet of working distance, however these calculations show the 12mm doesn't leave much room for error and the 25mm might be a better choice.

I don't have any other sort of formula at hand to confirm this, but about the shortest extension tube I recall ever using used on my 300mm or 500mm lenses is a 36mm (from the Kenko set, Canon doesn't offer one this long). Even that only changes MFD moderately on the longest lens (I don't have a 400mm). You might want to use a couple tubes stacked for more extension.

NOTE: editing... Whoops! I read the wrong line in Lens Work III, bolded items above are changed and the italicized paragraph is added.

for the 400 f5.6 L the MFD is about 11 ft (11.5 by the spec). Adding a 12mm tube, the MFD does not change too much, decreasing to perhaps 7 ft. The infinity focus with the extension tube is then about 50-60 ft.

You might try this... http://eosdoc.com/jlca​lc/

Thanks so much for your help. I will probably get the kenko set

Janie

Wilt wrote in post #11548189
You might try this... http://eosdoc.com/jlca​lc/

Wilt

Nice link.

Thanks

jag757 wrote in post #11547826
I'm wanting to do some backyard birdin with the 400 5.6 lensand my distance is little less than 10 ft. Could someone tell me what the mfd would be if I added a 12mm ext tube?

I tried a 12 and 24mm on my 400 f5.6 a couple years ago. I found it to be to constraining for what I got out of it.

Windpig, constraining in what way?

jag757 wrote in post #11548948
Windpig, constraining in what way?

I didn't feel comfortable locked into the minimum and maximum focus distances that the tubes provided. It was a couple of years ago, so maybe I should give it another shot. I've been thinking of getting the 300 F4 IS to provide a bit better MFD and IS. I do a bit of close up flower shots.

I've had a hard time choosing between the 300 f4 and the 400 5.6. I don't plan on using the ext tubes all the time, just when shooting at the feeders, and then, maximum focus distance will not be an issue. I am too close without the tube, though.

Would also like to try with a 1.4 TC. I know I'll loose AF with the 400 and wouldn't with the 300, but I think I would rather have the extra reach. Any thoughts?

jag757 wrote in post #11554085
I've had a hard time choosing between the 300 f4 and the 400 5.6. I don't plan on using the ext tubes all the time, just when shooting at the feeders, and then, maximum focus distance will not be an issue. I am too close without the tube, though.

Would also like to try with a 1.4 TC. I know I'll loose AF with the 400 and wouldn't with the 300, but I think I would rather have the extra reach. Any thoughts?

Some of the best birds shots I've gotten have been with my 70-200 F4 IS, only that I use it as a walk around lens and it's when I usually see the little song birds. Best birds shots for me have been grab shots of a towhee, bewick's wren and hummingbird at 200mm.