Extension Tube Magnification (More Pictures)

[Scottes]

This time to give an idea of the magnification abilities of tubes.

100-400mm L IS set at 300mm. f/11, ISO 100. Camera was not moved during these tests, so they show the magnification potential of each. I picked a random distance, which was 12'6".

To measure magnification I measured from the leftmost part of it's nose directly across to the rightmost edge of it's wing.

No tubes.


With 12mm tube. Shows a 10% magnification over the tubeless version.


With 20mm tube. Shows a 15% magnification over the tubeless version.


With 36mm tube. Shows a 27% magnification over the tubeless version.



From a previous post ( http://photography-on-the.net/forum/...ad.php?t=28017 ) testing the 100-400 @ 300mm, showing close-focus abilities:

With the 12mm tube. Minimum focus is 55" to sensor. Max focus is now limited to about 35 feet.

With the 20mm tube. Minimum focus is 51-1/4" to sensor. Max focus is now limited to about 21 feet.

With the 36mm tube. Minimum focus is 44-1/2" to sensor. Max focus is now limited to 11 feet.

I don't think that I'll ever leave the house without my tubes from now on.

[Tom W]

With 11 feet of maximum focus distance, you won't need to leave the house.

Nice comparison. Can you try it on a shorter lens? My 12 mm tube works very well with the 17-40 lens, except that I get in so close that its hard to get light around the lens hood.

[aeroshots2003]

Thanks for your illustrative response Scottes.

I did not know that the extension tubes also shorten the max focussing distance. I may consider buying one (or more) second-hand just for creative use.

Greetz,


Johan

[Scottes]

Originally Posted by Tom W

With 11 feet of maximum focus distance, you won't need to leave the house.

Nope. Gives me great shots at the birds visiting the feeders.

Originally Posted by Tom W

Nice comparison. Can you try it on a shorter lens? My 12 mm tube works very well with the 17-40 lens, except that I get in so close that its hard to get light around the lens hood.

Yeah, it gets a little crazy, huh? I tried a 36mm on my 70-200 @70mm and the subject was 1/4" from the hood. With something like a 17-40 tubes seem to be close to insane, since being so close means your DoF would be about .0000000001"

And if you put the 36mm tube on the 17-40 then you'd have to put the lens *through* the subject.


I think a lot of people think that tubes are for macro, but a small tube can help for closer subjects like small birds. With my example, a 36mm tube gains a 27% magnification with no loss. Even at 400mm, the tube theoretically puts the f-stop over the limit of AF on a 10D, but I had no problem autofocusing. The magnification is getting close to that of a 1.4 TC, but without the cost of [so much] light loss and since tubes have no optics you don't get aberations or image degradation.

Even a small tube on a big lens (12mm on a 300mm) gets some magnification (10%) so if you're shooting small-to-medium birds it's a cheap accessory in money, light, and image quality. A set of Kenko tubes (12, 20, & 36) cost less than half that of a Canon 1.4 TC.

Not too shabby if you can afford the loss of focusing to infinity.

[jim monroe]

Nice informative post.
Let me see if I have this straight because there are some new things I've learned that can be useful and some what surprising.
As far as extension tubes, I of course get some magnification but also the minimum focusing distance is reduced (which at times can be a good thing) while at the other end there is no longer focussing to infinity but to some finite value. Of course no glass in an extension tube so in that sense no loss of quality but some loss of light occurs. I was rather surprised about still being able to use autofocus. I have a 400mm f5.6 canon lens and with either the 1.4 or 2.0 teleconverter I loss autofocus perhaps using an extension tube I will not. I just got my set of extension tubes and have used them only on small focal length lenses I'll have to try this on my 400mm later today.

For the teleconverter as I said I lose light and hence for the above lens lose autofocus. Of course I can still focus to infinity which almost seems to be the only advantage over the extension tube. Of course in some cases focussing to infinity is critical.

[Tom W]

Originally Posted by Scottes

Nope. Gives me great shots at the birds visiting the feeders.

Yeah, it gets a little crazy, huh? I tried a 36mm on my 70-200 @70mm and the subject was 1/4" from the hood. With something like a 17-40 tubes seem to be close to insane, since being so close means your DoF would be about .0000000001"

And if you put the 36mm tube on the 17-40 then you'd have to put the lens *through* the subject.

Yeah, I'd probably have to mount the subject on the back of the lens where the gel filters are supposed to go.

I think a lot of people think that tubes are for macro, but a small tube can help for closer subjects like small birds. With my example, a 36mm tube gains a 27% magnification with no loss. Even at 400mm, the tube theoretically puts the f-stop over the limit of AF on a 10D, but I had no problem autofocusing. The magnification is getting close to that of a 1.4 TC, but without the cost of [so much] light loss and since tubes have no optics you don't get aberations or image degradation.

Even a small tube on a big lens (12mm on a 300mm) gets some magnification (10%) so if you're shooting small-to-medium birds it's a cheap accessory in money, light, and image quality. A set of Kenko tubes (12, 20, & 36) cost less than half that of a Canon 1.4 TC.

Not too shabby if you can afford the loss of focusing to infinity.

I'm goiing to have to do some experimenting - I only have a 12 mm Kenko tube, but I'm going to have to try it with my Sigma 70-200 and 1.4 TC. I just got the TC and it works very well with that lens. This could be interesting....

Thanks for the info.

[Scottes]

Originally Posted by jim monroe

For the teleconverter as I said I lose light and hence for the above lens lose autofocus. Of course I can still focus to infinity which almost seems to be the only advantage over the extension tube. Of course in some cases focussing to infinity is critical.

A 1.4 TC will give you more magnification - that's kinda simple.

But more importnatly, I think it's not just the loss of inifinity, but just how darn close "infinity" becomes with extension tubes. 300mm + 36mm means about 12 feet max focus, 27% magnification. 400mm + 36mm is about 18 feet and I'm gonna guess about 20-22% magnification. If you shoot subjects at such close distances you're fine. That's pretty close.

300mm + 12mm and max focus is about 35 feet - for a measly 10% magnification. 400mm + 12mm and max focus is about (wild guess from a field test) 50 feet, and probably 7% magnification.

I'm not so sure that 7% magnification is going to make or break a shot like 25% might. But it would sure stink if I suddenly wanted to focus on something 200 feet away and I lost the shot because I had a tube on.

Tubes don't cover all situations like a TC will. But in the right situations I'd say they're priceless, and you don't pay a penny in image quality.

[jim monroe]

I have finally been able to try an extension tube with a long focal length lense, my 400mm 5.6L, and really see the effect of the max. focus distance and on the other end being able to focus at shorter distances which in some situations for me is a great advantage. Still have a lot of experimenting to do but might be helped with some questions.

In the first post in this series there are four photos the last with the 36mm extension tube. All, as I understand it, were taken at 12'6" yet later it is stated for this extension tube max. focus distance is 11'0". Either I messed up or there was some mistake because the fourth picture is in focus. Figuring there may have been some formula used for max. focus distance which is in fact not correct. Can anyone straighten me out about what seems to be an inconsistency?

Like I said I need a lot more time experimenting with this kind of setup. It looks good, as suggested above, for small birds at feeders or someplace where you can get rather close. What about depth of field. My small amount of knowledge based on macro photo says get less depth of field, is it drastic?

[Scottes]

Originally Posted by jim monroe

In the first post in this series there are four photos the last with the 36mm extension tube. All, as I understand it, were taken at 12'6" yet later it is stated for this extension tube max. focus distance is 11'0". Either I messed up or there was some mistake because the fourth picture is in focus. Figuring there may have been some formula used for max. focus distance which is in fact not correct. Can anyone straighten me out about what seems to be an inconsistency?

ROFL in a bad way - I didn't notice that I wrote that. I will have to re-test that.

One thing that may be causing this is autofocus. At the extreme ends - both near and far - AF doesn't work so well. But if you manually focus you can get it focused. At the far end this may be because the camera won't AF "past inifinity" but you can manually focus until the lens stops. Maybe.

Like I said I need a lot more time experimenting with this kind of setup. It looks good, as suggested above, for small birds at feeders or someplace where you can get rather close. What about depth of field. My small amount of knowledge based on macro photo says get less depth of field, is it drastic?

DoF is affected, but it would depend on how close you are. If You are within normal focusing distance of the lens but you're using a tube to get a little magnification then DoF will barely be affected. But if you're using the tube to get closer than the lens' normal minimum focus distance then DoF will be affected in relation to how close you get. A 36mm tube on a 100mm lens will allow you to get within an inch of the subject - DoF is going to be pretty small. On the other end a 12mm on a 400mm lens at 5' from the subject won't affect DoF much over what the lens would normally produce.

Focal length and distance play huge parts in DoF calculations. A 400mm with a 12mm isn't changing focal length much, but a 36mm on a 100mm lens certainly is. Then as you get closer and closer the DoF will change also. There's no formula that I could find to calculate this.

[Andy_T]

Interesting subject, but you people certainly don't make it easy for us metric guys.

Ever wondered why you're talking about a 100-400 and not about a 3.93"-15.74" lens? Or a 2.28" instead of 58 mm filter thread? Be consistent (and use some civilised way to indicate distances), goddammit

'Infinity' is ok.

Best regards,
Andy

[xinther]

Scottes,

I understand you can combine two tubes, or all three. Can you try it and post pics, if possible?

Thanks,

Carlos

[Belmondo]

Originally Posted by Andythaler

Interesting subject, but you people certainly don't make it easy for us metric guys.

Ever wondered why you're talking about a 100-400 and not about a 3.93"-15.74" lens? Or a 2.28" instead of 58 mm filter thread? Be consistent (and use some civilised way to indicate distances), goddammit

'Infinity' is ok.

Best regards,
Andy

You 'metric' guys are such a bunch of whining weenies (a little alliteration for affect).

What do you stick in your shoes every morning? Feet, not meters.
Would do you ever call soccer? Meterball? Heavens no!
And who ever heard of someone with a meter fetish? Never in polite society.

And don’t get me started on this whole Celsius vs. Fahrenheit business. As it is, Canadians don’t have a clue how cold it really gets up there in the winters, and then they start bellyaching about the heat when it hits 30 degrees. (C, of course).

[Andy_T]

Originally Posted by belmondo

You 'metric' guys are such a bunch of whining weenies (a little alliteration for affect).

Pekka, quick! They're bashing us Europeans, again


(More of them than ever before, since yesterday ... 450 millions and counting )

Best regards,
Andy

PS: ... well, maybe I have to subtract the Brits ... after all, they were the ones who started that pound/inch/feet/stone/whatever business.

[Scottes]

From now on I'll measure everything in cubits, OK? The Egyptians were pretty early measurers, so they must be right, eh?



Personally I have to agree that the metric system is the right system. It's too bad that us silly Americans can't handle it as a general rule.

[Scottes]

Originally Posted by xinther

I understand you can combine two tubes, or all three. Can you try it and post pics, if possible?

100-400 @ 400, all three tubes (68mm), and a 500D:





Sorry, I guess I can't find any pics I took with this rig.