EF extender stacking

Started 3 months ago | Discussions thread
OP J.K.T. Regular Member • Posts: 301
Re: EF extender stacking

John Crowe wrote:

This all getting a bit confusing and I have asked you another question above too. You were talking about stacking 2x adapters but here you seem to be stacking two 1.4x extenders using the RF - EF between them, for an FD 500/4.5 L. Providing you a 1000mm f9 lens.

So, if you can put the EF 1.4x II onto the adapter onto the RF 1.4x then you can put any Canon EF 1.4x or 2x onto the adapter and RF 1.4x II as well.

That was my conclusion as well after the stacking order confusion was cleared.

I find it hard to believe that the Canon FD 1.4x-A converted to EF is that bad, but lets explore other possibilities.

It is. Either it always was or something went wrong with the conversion to EF, which took place was before I got it. After I tried to stack another 1.4x behind the FD 1.4x, it became clear that this was NOT the way to go.

On absolute scale it is not that bad when used alone, but comparing with EF 1.4x II it is. The RF 1.4 is even better, though by a MUCH smaller margin. With these two the sharpness difference is visible near the corners. A high resolution body might show more. There is also more barrel distortion (about 4x more) and magnification difference as well (1.37 vs. 1.41), but that has no practical meaning. I'd love to try EF 1.4x III just to see whether it is closer to EF II or RF. I suspect the latter.

I use a Canon FD 800mm f5.6 L on Canon EF several ways. The first is an ultrathin adapter, they are rare, but they get you focus to about 400 feet.

How thin is that? I have 8mm thick. I won't go into build quality more than this: the pin that was supposed to activate iris lever didn't reach quite that far in.

Second is a Kenko FD -EOS 2x converter/adapter. They too are rare, but I managed to get mine for $30. I don't think the seller realized what it was. It is not as good as the Canon EF 2x but it is still extremely useful.

I'm somewhat picky about the extenders as I have plenty of old ones, which are not very good. With 2x I likely would accept EF III and RF.

Third is the Canon FD-EF 1.26x Converter. Again, extremely rare, but less sought after since mirrorless came along. Some are still trying to get over $1000 for it, but I got mine for $300. I think I saw one recently for $400. Extremely sharp and makes your lens about 625mm f6.3. The 1.26x has no space at rear since it has glass and it has protruding front element that is fairly long.

That is definitely an option ... hoping it is better than the 1.4x. I may have seen the same eBay offer, but missed it. That would likely work with RF extenders, because EF 1.4x does too.

I have to go back to my tests but it seems to me that the Kenko 1.4x is almost as good as the EF 1.4x in image quality. I did decide that it was a very useful option as I described above.

I was not too happy with mine. There are probably 10 versions of it, so some could be better ... or sample variation could be an issue as well.

The easiest way for you to get to 1000mm, if that is your plan, is the Kenko FD-EF 2x mounted to the lens and then mounted to EF-RF then mounted to camera. It should beat stacking 1.4x extenders. I can actually test this if you like, at least with Kenko 1.4x and Canon EF 1.4x.

P.S. What about simply getting the FD 2x-A and mounting it to the lens and onto an FD - RF adapter?

The reputation of the older Canon 2x extenders is not as good as the 1.4x, so I'll pass that. For fun I tested the FD 2x-B with pretty much expected results. I know - it is not meant for the long teles.

The really easy solution is RF 2x with modified RF to FD adapter and a bit of dremeling on the FDn. That WOULD work and would give the best quality. The required modification on the adapter is removal of the pin and on the FDn cutting the iris lever very close to the back plate and putting rubber pushing behind it in order to activate it. I'm just loath to damage the otherwise "pristine" FDn.

The RF 2x I'll likely get anyway as I have some microscope objectives with way more resolution than my camera has.

 J.K.T.'s gear list:J.K.T.'s gear list
Canon EOS 7D Canon EOS 7D Mark II Canon EOS RP Canon EF 135mm F2L USM Canon EF 300mm f/4.0L IS USM +13 more
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