Longest Extension Tube for EF lenses

Anyone know if there is a longer extension tube than the Kenko 36mm tube? I'm looking for a single longer tube to use with my 400 DO.

I have a set of Okepa (sp?) tubes. They are mostly metal, decent quality and fine when stacked for use with my 100L. However, stacking them doesn't really work with the 400 because although they are reasonably well made, there is enough give with such a lens to occasionally loose contacts which is usually not a big deal with macro, but not acceptable when using the 400. So the longest tube I have is 31mm. Not 100% sure if the Kenko set is worth upgrading to for an extra 5mm, but I probably will for the price if I can't find anything else - every bit extra length helps.

I guess I could also see if the Kenko are so well made and fit with no play that I can stack two and use them with the 400mm handheld.

I saw a variable 55-71mm, but only for Nikon and I think I want something more solid. Obviously I'm not too price sensitive for the right product.

I have used stacked extension tubes with various lenses to gain more magnification or closer focus. My main issue is reducing the minimum focus distance of my 800mm lens as it is 6 meters - too long for a couple of hides that I use.
The main thing that I have found is that the ranges at which you can focus reduce significantly as the tubes get longer and the AF can get a bit sketchy or even fail. Additionally whilst 2 extension tubes are adequately solid things get very flexible with 3!
These days I don't use more than 21/25mm of extension as the compromises get too great for my personal uses.

Incidentally I also have a really cheap set of plastic mount AF extension tubes for my lighter lenses (eg 100 Macro) and these give a much less play at the joints so all 3 can be used together (65mm). Plastic mounts have far less play in them as they are much more accurately made (moulded) but I wouldn't want to put too much weight on them. They would be fine for all your listed lenses except the 400 DO, 150-600 and I would use them with care on the 70-200. Mine were about $10 (in your money) off Fleabay.

Totally off topic but how are you getting on with the 400 DO Mk2? This lens is very high on my lust after list!

Thanks for that, good info. I find the DO does OK with the 31mm tube, at least for what I use it for, but I have noticed the AF is not as 'solid', especially in dimmer light, with the tube. Interesting about the plastic mount,. I wouldn't have thought initially, but it makes sense that they can be more cheaply made with precision.

I guess it wasn't 100% clear, but I'm looking for a longer tube to use with the 400 DO in particular (edited my post a bit). For everything else, the tubes I have are fine. But I can see that the AF may become too unreliable anyway with anything much longer than 30mm or so, even if it is just one tube. So perhaps I won't find a longer tube very helpful.

On the off-topic of the DO:

Yes, the DO is pretty darn nice. The only thing that I could complain about is that the AF is not that great in really low light (at least with the 5DIII). However, we are talking ~1/40s f4 ISO6400, so not really the usual shooting conditions one would use this lens in and I wouldn't even be shooting with the 7DII in that light. Once you get up to ~1/160s f4 ISO6400 the AF is fine.

After using the sigma (first lens over 300mm I've ever owned) for a couple of months and on an extended trip, I started lusting after the DO. I got good shots with the sigma but it just doesn't have the AF and IQ of the rest of my kit. This summer I got the chance financially to get the DO, it's my first and likely only 'big white' and I certainly have no intention of selling it, it's everything I hoped for. I'm not sure what else to say that hasn't been said already - it gives me a reasonably small and light 400/560mm option that is on par (or better than) with my other lenses. The sigma is good (actually surprisingly when I compared in controlled conditions at f8 with the DO), but in the field I just never quite got that IQ and AF that I got used to with my other lenses.

My only choice now is whether to keep or sell the sigma. As I said, on side-by-side comparisons it is certainly as sharp at f8 as the DO is at f4 @400mm and not all that far off at 600mm f8 compared to the DO + 1.4TC v1 @5.6. So it's not like it is a bad lens, but I'm not sure I'll use it with the DO as an option.

One other thing I would love for the DO is a smaller hood option. The lens itself is surprisingly small really and the front element is recessed for some protection, but a 2-3" hood option would be awesome for me.

How about a bellows?
http://www.ebay.com …noapp=true&chn=​ps&lpid=82

Hmm, I need AF. I have a macro lens, I just need a shorter MFD for some situations with the 400 DO and a bit less than a 31mm tube gives me (MFD is still well over 2m with the 31mm tube). If I add the 1.4TC, the MFD is back to close to 3m.

I can often get closer than that to small birds, so something like a 40-60mm tube would be nice - assuming I still get decent AF and can hand hold the combo 'in combat' so to speak.

Edward,
I have used my 400 f2.8 quite a bit for close-up work. The two lenses are similar in some ways, so maybe my experiences would apply to your needs.

I found that extension tubes are of negligible effect when working with a focal length of 400mm. One of the main reason extension tubes work is because they are adding focal length to the lens. So, if you add a 25mm tube on a 50mm lens you now have a focal length of 75mm - a big difference in field of view. When you add a 25mm tube to a 400mm lens you now have a focal length of 425mm - hardly any difference between that and the 400mm you started with. Sure, extension tubes also alter the way the optics focus the light, but the added focal length is a bigger factor in the equation than many people realize.

What I have found works far better than the extension tubes are the tele-extenders. They increase focal length without increasing the MFD. So, the MFD on my 400 f2.8 is 10 feet. When I put the 2.0x extender on, the MFD is still 10 feet, but I get far more magnification due to the much narrower field of view. Adding a 25mm extension tube hardly makes any difference at all in magnification; it only changes the MFD by about 1 foot 4 inches. But adding that 2.0x extender makes a whopping difference!

I really suggest you try the 2.0x for close-up work before you go nuts trying to find an extender combination that works. If you don't have one contact me; I may loan mine to you for a couple weeks if you'd like to try it out.

ejenner wrote in post #17738327
Hmm, I need AF. I have a macro lens, I just need a shorter MFD for some situations with the 400 DO and a bit less than a 31mm tube gives me (MFD is still well over 2m with the 31mm tube). If I add the 1.4TC, the MFD is back to close to 3m.

I can often get closer than that to small birds, so something like a 40-60mm tube would be nice - assuming I still get decent AF and can hand hold the combo 'in combat' so to speak.

I've tried the Kenko 36mm + 25mm stacked at 61mm, and AF was horrible with the 400/4DO II at the new min focus distance (though fine near max). The AF would oscillate back and forth. That may have been under overcast skies, though, IIRC. That was with 7D2 in one-shot mode with spot AF; may have been better with a wider AF.

Sorry, Tom - Extension tubes don't change the focal length of a lens. They change the lens extension; you lose infinity focus but get to focus closer up than the basic lens will allow you. That's why you can find birders using tubes on their super-teles to get those small birds just a few feet away. For instance, 25 mm of tubes will get you about 60 cm (2 ft.) closer at minimum focusing distance on a 400 mm Mk. II. So from a bit under 9' to just over 6'. Not too shabby. Teleconverters actually alter the optics of the combination lens, without affecting the closest focus distance. And they cost you 1 or 2 stops of light, which tubes don't, while also increasing your vulnerability to camera/lens shake due to the longer focal length.

I got my Sigma APO EX DG 2 x TC for $150 used. It's about 51mm length.
There are quite a few POTN members who would be capable of removing elements and electronics, then restoring electrical contact function.
On my bodies at least (and my 100-400 II lens) it's a very good fit and has less freeplay than any other extenders I have (Canon 25mm tube, Canon 1.4TC II, Kenko extension tubes)

Just a thought.

Jon wrote in post #17739338
Sorry, Tom - Extension tubes don't change the focal length of a lens. They change the lens extension; you lose infinity focus but get to focus closer up than the basic lens will allow you. That's why you can find birders using tubes on their super-teles to get those small birds just a few feet away. For instance, 25 mm of tubes will get you about 60 cm (2 ft.) closer at minimum focusing distance on a 400 mm Mk. II. So from a bit under 9' to just over 6'. Not too shabby. Teleconverters actually alter the optics of the combination lens, without affecting the closest focus distance. And they cost you 1 or 2 stops of light, which tubes don't, while also increasing your vulnerability to camera/lens shake due to the longer focal length.

Actually, if you go by the typical, most commonly accepted definition of focal length, the addition of an extension tube does change the focal length of a lens. You are putting xx millimeters between the optical center of the lens and the focal point.....how can that possibly not be changing the focal length when the focal length itself is defined as the distance between the optical center of a lens and its focal point?

Just google "definition of focal length" and see for yourself. Here are several of the definitions that pop up:

The focal length of a lens is defined as the distance in mm from the optical center of the lens to the focal point, which is located on the sensor or film if the subject (at infinity) is "in focus".

fo·cal length
noun
noun: focal length; plural noun: focal lengths
. . the distance between the center of a lens or curved mirror and its focus.

The distance between the focal point of a lens (that is, the point at which the lens will focus parallel rays of light) and the lens itself.

Focal length (shown in red) is the distance between the center of a convex lens or a concave mirror and the focal point of the lens or mirror — the point where parallel rays of light meet, or converge.

The distance of a lens or mirror to its focal point. Also called focal distance, focus.

Tom Reichner wrote in post #17739637
Actually, if you go by the typical, most commonly accepted definition of focal length, the addition of an extension tube does change the focal length of a lens. You are putting xx millimeters between the optical center of the lens and the focal point.....how can that possibly not be changing the focal length when the focal length itself is defined as the distance between the optical center of a lens and its focal point?

Sorry Tom, you are in the weeds! FL is determined SOLELY by the optics (elements), and putting a telextender DOES change the optic (FL increased by mag factor of the TC),
but an extension tube merely puts SPACE between the focal plane and the rear element of the lens -- the very DEFINITION of 'focus' mechanics (in the days before AF lens made internal focus mechanisms depart from that traditional action)

Tom Reichner wrote in post #17739637
Just google "definition of focal length" and see for yourself. Here are several of the definitions that pop up:

The focal length of a lens is defined as the distance in mm from the optical center of the lens to the focal point, which is located on the sensor or film if the subject (at infinity) is "in focus".

fo·cal length
noun
noun: focal length; plural noun: focal lengths
. . the distance between the center of a lens or curved mirror and its focus.

The distance between the focal point of a lens (that is, the point at which the lens will focus parallel rays of light) and the lens itself.

Focal length (shown in red) is the distance between the center of a convex lens or a concave mirror and the focal point of the lens or mirror — the point where parallel rays of light meet, or converge.

The distance of a lens or mirror to its focal point. Also called focal distance, focus.

The distance from the REAR OPTICAL NODE to an image focused on the focal plane with a target AT INFINITY, is what is meant by that. You have taken it out of context.

Tom Reichner wrote in post #17739637
Actually, if you go by the typical, most commonly accepted definition of focal length, the addition of an extension tube does change the focal length of a lens. You are putting xx millimeters between the optical center of the lens and the focal point.....how can that possibly not be changing the focal length when the focal length itself is defined as the distance between the optical center of a lens and its focal point?

Just google "definition of focal length" and see for yourself. Here are several of the definitions that pop up:

The focal length of a lens is defined as the distance in mm from the optical center of the lens to the focal point, which is located on the sensor or film if the subject (at infinity) is "in focus".

fo·cal length
noun
noun: focal length; plural noun: focal lengths
. . the distance between the center of a lens or curved mirror and its focus.

The distance between the focal point of a lens (that is, the point at which the lens will focus parallel rays of light) and the lens itself.

Focal length (shown in red) is the distance between the center of a convex lens or a concave mirror and the focal point of the lens or mirror — the point where parallel rays of light meet, or converge.

The distance of a lens or mirror to its focal point. Also called focal distance, focus.

You're misreading that. If you attach an extension tube you don't change the infinity focus of the lens. A 400 mm lens remains a 400 mm lens; you'll just remove the ability to focus at infinity when you have the tube in place. Focal length is a property of the glass, not the tube containing it. "Parallel rays of light" would be emanating from a light source at infinity.

I stand by my words and declare that anything to the contrary is incorrect, according to the literal definition of focal length as I quoted it.

If you want to go by a different definition of "focal length", then fine. If you want to add something to the definition of "focal length", then fine. But if going by the definition(s) I quoted, and not adding anything else to them, then adding an extension tube DOES change the focal length.

Why? Well, as you say, adding an extension tube is adding space between the lens and the point at which the rays of light are focused (the sensor or film). Would you agree that adding the extension tube also adds distance between the lens and the sensor? Well, focal length is an actual measurement - it is the distance between two things. If you add more distance between the two things, then one would have to agree that the overall distance has been increased, right? And if the distance has increased, and that distance is the very measurement by which focal length has increased, then according to the principles of logic, the focal length also increases.

Focal length really is a distance as measured in millimeters......someh​ow it seems that you are thinking that it is something different than that, or something more than that. But when you look at the actual words used in the definitions you really can't make that case, unless you add to those words or change those words or claim that those words really mean or imply more than what they actually say.

Sorry, Tom, that's wrong. You're only getting your misinterpretation of "focal length" by leaving out the "at infinity" part of the definition. Ask any HS physics teacher.

The focal length of a lens is defined, absolutely and only by the distance from the lens' optical node to the image when that lens is aimed at a subject at infinity, from which the light rays reaching the lens are essentially parallel. If you focus on an object that is closer than infinity, you will have to move the optical node away from the image plane where the image is formed but you will not change the lens' focal length. This is shown by the basic optical formula:
1/f=1/I+1/O where f is the lens' focal length, I is the distance from the lens optical node to the image plane and O is the assistance from the lens optical node to the subject. What you're getting by adding 25 mm of extension tube to a 400 mm lens is a new value for "I". But try focusing that 400 mm lens + 25 mm tube on a subject at infinity. You can't do it.

Interesting discussion! And I'm...