Quick question on Canon teleconverters

Can you stack 1.4xII with another 1.4xII and only lose 2 stops of light? If yes, wouldn't this actually be better than having only 2xII and losing 2 stops? Should the IQ take major hit if two 1.4x II's are stacked? At least the FL is 2.8x not 2x...

its actually 1.96X when stacked

They are multiplicative not additive

You cannot stack two Canon 1.4x teleconvertors, as they have front elements which project forward too far to fit in the backside of another 1.4x teleconvertors. (You can stack a Kenko 1.4x behind a Canon 1.4x.)

That is right gotaudi... and thanks for the confirmation Wilt.

Nevermind the original question.

When they say it is a 1.4x Tc they actually meant square root of 2 and abbrev. 2 1.4x TCs is the same as a 2x TC. More glass though. Shooting wide open the 2x TC will be better, stopped down a ways it is a horse race. You can stack Kenko and Tamron TCs.

Just out of curiosity, Canon 1.4x II + Kenko 1.4 is better than Canon 2x II? I just don't like the amount of IQ degradation when used with Canon 2x II & III...

I realize your questions are in regards to using the Canon extenders but i did recently perform some rather extensive testing using the Kenko converters and a Vivitar 2x MC7 that gasrocks mailed me for testing also.

You can view the stacked results below and a variety of other converter tests performed on both the 70-200MKII & 100-400L lenses in my signature:

Stacked Tests here:

https://photography-on-the.net …p?p=11887106#po​st11887106

Regards,

Since Silverfox1 posted results with stacking 2x and 1.4x teleconvertors, I will offer the results of stacking two 1.4x teleconvertors, with 70-200mm f/4 IS lens...camera position moved to keep subject fixed in size for direct comparison reasons.

lens only:

Thank you Silverfox1 and Wilt.

Hey Wilt, would you happen to have the 100% cropped comparisons?

You are already looking at only about 10% of the frame ...the (artificial) flower filled the center circle of the viewfinder -- it is what I used as the way to determine 'same size' as I moved the camera back with increased FL.

Hey Wilt, then they look pretty darn good to me! How would you rate Canon 1.4x + Kenko 1.4x VS Canon 2x?

joonrhee wrote in post #12138634
Hey Wilt, then they look pretty darn good to me! How would you rate Canon 1.4x + Kenko 1.4x VS Canon 2x?

I cannot comment, having no experience with the 2x teleconvertors on my lens. It would be speculation.

If you are stopping down the lens a bit - the combo you mentioned will be just fine. I used to have 2 identical Tamron SP 1.4x TCs for that reason - they fit everything and can be stacked.

joonrhee wrote in post #12138634
Hey Wilt, then they look pretty darn good to me! How would you rate Canon 1.4x + Kenko 1.4x VS Canon 2x?

Just remember your best IQ when either stacking two 1.4 TC`s or a single 2x on a fixed f2.8 lens will be F8.0 & F11.0

Regards,

joonrhee wrote in post #12119546
Can you stack 1.4xII with another 1.4xII and only lose 2 stops of light? If yes, wouldn't this actually be better than having only 2xII and losing 2 stops? Should the IQ take major hit if two 1.4x II's are stacked? At least the FL is 2.8x not 2x...

Sure, it is even better to use 1.x extensers. Each does not loose any stops and does not intorduce any quality loss because it is 1.x. Since you do not need to do anything to get that 1.x magnification you virtually already have as many 1.x extenders as you need. They all have zero length and weight zero lbs.

So if you stack five of them you turn your 135 /2.0 into EF 650/2.0 !