ef300mm F4L IS USM + extension tube ef25 II

Anyone using this combo? Can anyone post a pic? What do you guys think of this combo?
trying to find a way for a cheaper macro just for fun..

A 25mm tube on the 300mm lens will only slightly decrease the lens' closest focusing distance, i.e. modestly increase it's magnification.

The longer the lens' focal length, the more extension you'll need to make a significant difference. Rough estimate without doing any math, you'd need 300mm of extension to get anywhere close to 1:1 magnification with a 300mm lens. (Actually less in this case, because the lens is already inherently pretty close focusing. But still a lot would be needed... I'd guesstimate at least 100mm, maybe 150mm of extension... or four to six of those Canon tubes stacked.)

The 300/4 IS has 0.24X magnification without any tube... 0.37X with a 25mm tube added. That's a change of roughly 50% greater magnification... Or to put it another way, it would be like cropping off about 1/3 of what you see through the viewfinder with the lens now, leaving the central 2/3 of the image area. Heck, you can trim an 8x10 or 11x14 from an 18MP 7D that much, without any significant loss of quality.

It would be a wee bit more effective to put the 25mm tube behind your 70-200mm... that will give you 0.39X on the non-IS version or 0.42X on the IS version of the lens (you don't indicate which version you have). On your 50mm lens a 25mm tube would get you to 0.68X mag. In my experience, using an extension tube on the 50mm makes for some vignetting and soft edges/corners... it's simply not a flat field lens, so forcing it to focus so close causes this. Both effects can be useful, though, depending upon the particular subject. I have 70-200/2.8 IS, so can only speak to that lens, there's little or no vignetting or loss of edge sharpness with 25mm tube on it.

Want more magnification? Maybe get the Kenko tube set and use the longer 36mm tube it includes, or stack two or three of those tubes together for even more extension. The Kenko tube set costs a bit more than a single Canon 25mm, but you get three tubes in different lengths that are a lot more versatile.

If you go with the Canon, unless you plan to use it on one of your EF-S lenses, you could save a little by getting a used 25mm (not II).... That's identical, except it doesn't accomodate the EF-S mount lenses.

Same with the Kenko... the older set marked "CA/AF" works fine with all EF lenses... but not with EF-S. For that you'd need the newer ones markes "CA/AFs", note the small "s" added.

However, personally I don't see much reason to use an extension tube behind the EF-S lenses you list. Doesn't make a lot of sense behind a 10-22 (even 12mm will put you so close the lens is literally touching your subject, at the wider end of the zoom range). And, you have better alternatives than the 18-55... in your 50mm and 70-200.

There are also the relatively inexpensive Zeikos tubesets, that sell under their own name and many others (ProOptic/Adorama, Vivitar, yada, yada). Same thing. The cheapest ($50-60) have plastic bayonet mounts and I would pass on those personally. The better ones have metal mounts, cost a little more ($75-90). But, I wouldn't use any of these with a heavier lens like 300/4 or 70-200. They are plastic-bodied and the latch mechanisms leave me a little nervous.

The Canon and Kenko are very similar in construction and quality. I've used them behind up to 300/2.8 and 500/4 on occasion, with no problems.

Thank you for the explanation.....I appreciate it, My 2 choices are kenko and canon and heard good things with Kenko. Maybe with a little more money I would go with kenko set instead.

Thanks again.

You can get non-Kenko sets with contacts (AF, aperture control etc..) for $80 that work well - I have 12, 21 and 32mm tubes. They MIGHT not be quite as solid as the Kenko, but I've not heard of people having problems with them and I've been using mine for 2 years. Mine are metal, but I haven't sen the make around again - probably changed and marketed as something else. They are fine with my 70-200, but I would use a tripod collar with any of the larger lenses anyway.

But Kenko are really the 'gold standard'. I don't hear of many people even bothering with the Canon ones.

I use this combination all the time for shooting birds at close distances as well as butterflies and dragonflies. The extra magnification is noticeable, and it still focuses out to around 20 feet or so.

Try sticking your 1.4x behind the 300mm f/4 IS. It will leave the minimum focussing distance unchanged but increase the focal length, and therefore the magnification, by 1.4.

I found it worked better with a TC, focussing was faster and more reliable. Macro work usually means stopping down below f8 anyway. I ended up selling mine, it is not a replacement for a good macro lens.