I've purchased the 1.4x Canon extender for my (on backorder) 135L, but by curiosity, I've tried yesterday to use it with the MP-E 65mm and... it works! The result is that the magnification is multiplied accordingly up to 7x.
I've just tried to make a few attempts with it, but the result is quite disappointing however at highest magnification: very soft pictures.
But the result is quite good up to 3x1.4=4x, but this is obviously useless as you can achieve higher magnification without the 1.4 extender
As I didn't spent much time trying to make it works better, I'm interesting to know whether anybody has tried to use the combo with some success at 5-7x?
If I ever found another subject, I'll try using f/2.8 and f/4. At that kind of magnification, I think it's the diffraction that hurt it more than the IQ degradation from the TC.
As I like shallow DOF a lot, I most of the time use a wide aperture... this is a good point. I've used f9 here.
But I don't think this is the point. In fact "soft" is probably not the correct wording: as you can see on the picture below, this looks like a ghost effect. This picture has been taken on a tripod with a remote trigger and if I remember well mirror lockup enabled, and focus has been set using live view mode... this is not a focus or camera shake problem.I think.
I believe that, when used with the MPE, the Canon 1.4x is non-reporting. In other words, it doesn't show that the aperture has been reduced by 1 stop. (At least I assume so since it still showed a max aperture of f/2.8 when I tried it on mine). This means that you have to be ever more careful of diffraction effects at high magnifications.
At 5x magnification your effective f# is 6 times the indicated value, even without a TC. Stick a TC on and your magnification is 7x, the actual aperture with a non-reporting extender is 1 stop more than indicated, and the effective aperture is 8 times that. So doing the math that means that at 7x your maximum aperture is f/4 and the effective aperture is f/32 - wide open.
What all this means is that at really high magnifications like this you are caught in an ever narrower trap between limited DOF and limited sharpness due to diffraction. You can get still get quite decent sharpness in a macro setting with effective apertures in f/22-32 range (depending on pixel pitch), but much beyond this level sharpness will really start to suffer.
So in short I do not believe there is any problem with your lens or TC, but with the regime in which you're trying to use them. At such high magnifications you have the choice of very shallow DOF, reduced sharpness, or focus stacking to mitigate these effects.
This is thus probably a diffraction issue: according to you math, at f9, the effective aperture is f72 which is plenty enough to get into diffraction troubles
I don't think that ghosting in the f/9 photo is caused by diffraction though. Diffraction just makes the image very soft, not ghosting like that. Here's some examples of 5x mag, f/8@6s and f/11@10s, as you can see, no ghosting. Chances are your tripod wasn't as stable as you might think. Did you set the shutter at 2 seconds delay for the mirror lockup to work? http://farm4.static.flickr.com/3030/2934393774_bd8839f912_o.jpg
n0b0 wrote:
Did you set the shutter at 2 seconds delay for the mirror lockup to work?
Huh... no
I usually don't use mirror lockup as I mostly shoot handheld and I forgot that point. And you are correct: my tripod was not that steady. It was just a quick test and I guess I should try again a little but more seriously.
