So just wanted to show a quick size comparison between 200 & 400mm focal lengths when taking a picture of the moon.

Camera settings are slightly different but the picture on the left was taken with 70-200 F2.8L IS II USM & a Canon 2x extender lens at 400mm while the right picture was done with the F4L IS USM lens at 200mm.  The contrast seems slightly better on the right on the first picture but then again the settings were different and it’s possible that atmospherics could have played a role in sharpness.  Digitally zoom the 200mm to 400mm and the clear winner is the image where an extender was used.

I sold the 70-200 F4L IS USM so I can’t do any comparisons with that lens but the next clear night I’ll do these tests again and see if I get the same results.  I may also try the Canon Rebel SL2, with its APS-C sensor and the 1.6x crop, that would get me to a massive 640mm!

Can’t wait for the next night with clear skies!