Canon Extension Tubes... A Couple of Questions.

68lbs

68lbs

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April 2008
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I sold my Canon 100mm Macro about 12 months ago due to lack of use, but am now considering Canon extension tubes as I would like the option to focus closer with both my 50mm f/1.4 and 70-200 f/2.8

I am specifically considering the official Canon EF12 II and EF25 II.

My questions...

1. What is the difference between the EF12 and EF25? Other than 13mm! :shrug:

2. Does IQ suffer when using an extension tube?

3. Is AF speed affected?

4. Is maximum aperture affected like when using a TC?

5. Is the far limit of focusing affected? And if not, is it feasible to permanently have one on with say my 50mm f/1.4 - would be a pretty creative walkabout for me with limit DoF and close-up opportunities! :)

Any help appreciated.
 
Just buy a set of Kenko tubes. Usually come as a set of three which can be used individually or stacked. Focus range is tiny so no use for anything apart from macro.

I found best way was to turn AF off and just move back and forth until in focus.
 
68lbs said:
I sold my Canon 100mm Macro about 12 months ago due to lack of use, but am now considering Canon extension tubes as I would like the option to focus closer with both my 50mm f/1.4 and 70-200 f/2.8

I am specifically considering the official Canon EF12 II and EF25 II.

My questions...

1. What is the difference between the EF12 and EF25? Other than 13mm! :shrug:

They increase the distance between the lens and the sensor plane thus allowing closer focussing, the larger the increase the closer the focus, thus the 25mm tube will allow you to focus closer than the 12mm tube.

2. Does IQ suffer when using an extension tube?

No!

3. Is AF speed affected?

It can be depending on how much of an extension is used.

4. Is maximum aperture affected like when using a TC?

Not per say, although there is a drop in the amount of light reaching the sensor plane due to the further distance it has to travel.

5. Is the far limit of focusing affected? And if not, is it feasible to permanently have one on with say my 50mm f/1.4 - would be a pretty creative walkabout for me with limit DoF and close-up opportunities! :)

Yes, it is rare that a lens will focus to infinity with a tube attached, there can be exceptions to this if a lens has a focus limit beyond infinity and a short tube is used.

Any help appreciated.
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Hope this helps!
 
EdBray said:
4. Is maximum aperture affected like when using a TC?

Not per say, although there is a drop in the amount of light reaching the sensor plane due to the further distance it has to travel.
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Eh? I thought it was because you were spreading available light over a greater area... ends the same though, a darker image.
 
Oops! Crossed post with, erm, everybody!
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68lbs said:
I sold my Canon 100mm Macro about 12 months ago due to lack of use, but am now considering Canon extension tubes as I would like the option to focus closer with both my 50mm f/1.4 and 70-200 f/2.8

I am specifically considering the official Canon EF12 II and EF25 II.

My questions...

1. What is the difference between the EF12 and EF25? Other than 13mm! :shrug:
Click to expand...

Nothing.

2. Does IQ suffer when using an extension tube?
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There is no optical interference obviously, but you are taking a lens designed for distant focusing down to macro levels it was not primarily intended for. So yes, quality will be degraded. Some lenses take to it quite well, and probably both your lenses would be okay. I use a set of Kenko tubes on my 70-200L 4 IS very successfully. Wide-angle zooms are not so good.

3. Is AF speed affected?
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Yes, because it has to move a long way at close distance. But that doesn't matter because you will almost certainly be focusing manually. That is, focus roughly by hand and then rock your body back and forth very gently to achieve optimum sharpness. That's the way most people work in macro.

4. Is maximum aperture affected like when using a TC?
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Yes, when you get down to 1:2 half life size, you lose one stop. When you get to 1:1 life size it's two stops. Same as a regular macro lens.

5. Is the far limit of focusing affected? And if not, is it feasible to permanently have one on with say my 50mm f/1.4 - would be a pretty creative walkabout for me with limit DoF and close-up opportunities! :)
Click to expand...

Yes, you lose distance focus. You can't have it all ways. You need to fit the right tube, or combination of tubes, for each particular shot. Kenkos are pretty good, fully automatic, and good value at around £120 for a set of three.

Any help appreciated.
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Ambermile said:
Eh?
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The maximum aperture does not change, but the amount of light reaching the sensor will be reduced dependant on the amount of extension used. IIRC, At a ratio of 1:1 it is about a 2 stop loss. When you go into super macro ratios it can be very difficult to actually see your subject due to light loss!

This is due to the inverse square law and the extension to the lens from the focal plane.
 
Yes, but nothing to do with the light running out because it's got too far to go! Like, that 12mm makes a difference after the millions of miles from the sun... anyway, as you then say, the inverse square law covers it nicely. Not the amount of light reaching the sensor because it's to far, but because it is spread out more "thinly" if you like - *because of the inverse square law*

Arthur :D
 
68lbs said:
5. Is the far limit of focusing affected? And if not, is it feasible to permanently have one on with say my 50mm f/1.4 - would be a pretty creative walkabout for me with limit DoF and close-up opportunities! :)
Click to expand...

Some numbers to digest before parting with your hard earned cash.

Your 70-200 with an EF12 will give you the following;
At the wide end (70mm) you'll have magnification of 0.22-0.17x with a working distance of 306-372mm between minimum focus and infinity.
At the tele end (200mm) you'll get 0.22-0.06x magnification with a working distance of 914-3145mm between MFD and infinity.

An EF25 with the lens set to 70mm gives 0.41-0.38x with working distances of 138-143mm....a very narrow range and pretty much unusable
At the long end, you'll have 0.3-0.14x with working distance range of 694-1466mm

On to your EF50/1.4....
With the EF12 you'll get 0.39-0.24x with 142-226mm working distance between MFD and infinity.
An EF25 will give 0.68-0.53x with a working distance range of 82-110mm...as you can see, not really useful to keep on there for non-macro shots.

HTH

Bob
 
Thanks for all the quick replies chaps :)

Is there a way to work out the minimum focus distance for a particular lens/tube combo if you know the tube length and existing min focus distance?

I'm not really after them for Macro in the 'Alby' sense of the word to look up the arse of a flea, more that I'd just like to be able to focus a bit closer to take still life shots and have closer creative options for things like my christmas cake series.

Tubes are what I'd be best with, yeah?
 
Ambermile said:
Yes, but nothing to do with the light running out because it's got too far to go! Like, that 12mm makes a difference after the millions of miles from the sun... anyway, as you then say, the inverse square law covers it nicely. Not the amount of light reaching the sensor because it's to far, but because it is spread out more "thinly" if you like - *because of the inverse square law*

Arthur :D
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Actually Arthur that 12mm will make a difference as will any increase in the rear of lens to focal plane distance, you are not extending the amount of distance the light has to travel from the subject to the sensor by very much, but are increasing the amount of focussed light that has to travel from the rear of the lens to the film/sensor plane.

The amount of light reaching the subject has no bearing on the magnification provided you allow for the magnification when you take your exposure whether it be lit from the sun, a flash ot a candle. If you increase the lens to focal plane distance you will suffer a reducion in the amount of light reaching the sensor (due to the increase the light has to travel)!
 
Yes, I know that - hence why I was querying your statement that the light levels drop because it's too far to go!
 
68lbs said:
Is there a way to work out the minimum focus distance for a particular lens/tube combo if you know the tube length and existing min focus distance?
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In theory, yes. The downside is that lenses with internal extensions for focussing then you need to know the amount of internal extension to put into the equation....this data doesn't get published by the manufacturers.

Of course, you can calculate the internal extension but only by having the values I posted earlier.

Bob
 
68lbs said:
Tubes are what I'd be best with, yeah?
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That's what I use.

A set of Kenkos on your 70-200 will give you every option of magnification from a very slight increase right down to 1:1, and also a variety of working distances depending on focal length setting.

Edit: Kenkos are 12mm, 20mm and 36mm, singly or in any combination up to 68mm all together, which will give you 1:1 at 70mm on your zoom.
 
Slightly off topic, but related: Could one of you clever people tell me what the min and max focusing distances would be for an EF12 with a 600mm lens (on a 50D if that affects anything.) I have a set of the Jessops tubes (have used them on a siggy 120-300 in the past) but they seem a bit flimsy so was considering getting a Canon EF12 to use for close up "bird on a stick" type stuff.

Thanks, Tim.
 
tappilappi said:
Slightly off topic, but related: Could one of you clever people tell me what the min and max focusing distances would be for an EF12 with a 600mm lens (on a 50D if that affects anything.) I have a set of the Jessops tubes (have used them on a siggy 120-300 in the past) but they seem a bit flimsy so was considering getting a Canon EF12 to use for close up "bird on a stick" type stuff.

Thanks, Tim.
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An EF12 will give you 5.1 to 29.5 metres range, an EF25 will give 4.4 to 14.2 metres.....with an EF600/4

Bob
 
Thanks Bob. :thumbs:

Next question: :) Would the depth of field be affected (at min focusing distance) by the addition of the tube? (yup - with a 600mm f4.)

Thanks again. Tim.
 
Bob's provided the numbers. I quite regularly use tubes with my 500/4 to enable me to focus closer than 4.5 metres. If you are working to a set of perches, it can still give you good range, although I do find the AF struggles sometimes in low light with the EF25 (although not the EF12)

I used to have the Kenko tubes but didn't fancy hanging a 1-series body and a 500 with them in the middle so have EF12 and EF25 now... Unless you need compatability with EF-S lenses, then the MkI versions are fine and can been found second hand without too much effort.
 
Thanks Grumpybadger. I had the same thoughts about the Jessops tubes as you did about the Kenko. Are the Canon mk1 tubes metal mount as well? Also, does the focus preset still work with tubes? (Thinking fixed perches here.)
 
tappilappi said:
Thanks Bob. :thumbs:

Next question: :) Would the depth of field be affected (at min focusing distance) by the addition of the tube? (yup - with a 600mm f4.)

Thanks again. Tim.
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Certainly will Tim.....DoF is a function of aperture and magnification (which is increased as the MFD decreases)

Bob
 
So less DOF then? Also, what are the optical rules when a TC is added into the mix? I seem to get different results whether the TC is between the camera and the tube, or between the tube and the lens.

Once again, thankyou. Tim.
 
tappilappi said:
Thanks Grumpybadger. I had the same thoughts about the Jessops tubes as you did about the Kenko. Are the Canon mk1 tubes metal mount as well? Also, does the focus preset still work with tubes? (Thinking fixed perches here.)
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Canon are metal yes. I have a EF12II and a EF25 so one of each!

tappilappi said:
So less DOF then? Also, what are the optical rules when a TC is added into the mix? I seem to get different results whether the TC is between the camera and the tube, or between the tube and the lens.

Once again, thankyou. Tim.
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I've found the AF to work better with the tube against the camera, then TC and then lens - but I don't know why!
 
Thank you. I have been "playing" but with such shallow DOF/magnification/focal length I am unsure what is "trying to bend the laws of physics" and what is "operator error."

Mostly it has been the latter ... :bang:

Tim.
 
The tube should be against the body...distances quoted remain unchanged with the TC in the loop.

Bob
 
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