Stacking teleconverter and extension tubes

[dibbly dobbler]

Hi All.

Just playing around while it was wet out. I hadn't realised that you can stack teleconverters (at least the Kenko variety) and you can also stack teleconverters and extension tubes. News to me!

So I tried a few shots as per the below - no cropping, and the same pp applied to them all.


200mm by dibbly dobbler, on Flickr


200mm + 1.4tc by dibbly dobbler, on Flickr


200mm + 1.4tc + 36mm tube by dibbly dobbler, on Flickr

So...

First pic: 200mm on a 1.6x crop sensor = 320mm
Second pic: 200mm x 1.6 x 1.4tc = 448mm
Third pic: (200mm + 36mm) x 1.6 x 1.4 = 528mm ??

Not sure about the calculation for the last one - any thoughts ?

All look acceptably sharp (conditions not ideal as indoor with no flash so quite a slow shutter for the last two) and autofocus worked even with the 36mm extension tube inserted. The tube went onto the body, then the tc went between the lens and the tube.

Anybody else tried this ?

[dibbly dobbler]

Ah bugger - just realised it wont focus to infinity with the tube inserted, the max is about 15 feet. Poo.

[SamHH]

dibbly dobbler said:

First pic: 200mm on a 1.6x crop sensor = 320mm
Second pic: 200mm x 1.6 x 1.4tc = 448mm
Third pic: (200mm + 36mm) x 1.6 x 1.4 = 528mm ??

Not sure about the calculation for the last one - any thoughts?

The extension tube doesn't increase the focal length of the lens so the focal length remains 280mm in this case (200 x 1.4). It decreases the minimum focusssing distance, allowing you to fill more of the frame with the subject by getting closer. The same applies with or without the teleconverter, although that's not to say it isn't a useful combination for some photos.

[dibbly dobbler]

SamHH said:

The extension tube doesn't increase the focal length of the lens so the focal length remains 280mm in this case (200 x 1.4). It decreases the minimum focusssing distance, allowing you to fill more of the frame with the subject by getting closer. The same applies with or without the teleconverter, although that's not to say it isn't a useful combination for some photos.

Thanks Sam - they were all taken at exactly the same distance though so adding the extension tube certainly had the same effect as shooting at a longer focal length I think (ie the cat's head virtually fills the frame in the last one)

[Simpo Two]

Your cat must be stuffed!

[dibbly dobbler]

Simpo Two said:

Your cat must be stuffed!

Wish he was!

[davepoth]

He looks angry in that last photo.

[Simpo Two]

I think you're right.

Pic 1: 'Is this food?'

Pic 2: 'I don't think so, bugger.'

Pic 3: 'One inch closer and I'll fking have him'



Great looking cat BTW.

[dibbly dobbler]

He's a big soft lump - just pretends to look mean