Stacking TCs Followup

Posting this in response to some questions I've received about the quality of images one can get with stacked TCs. I've posted two bluebird shots recently in the avian forum that I got with stacked Canon 1.4x and 2x TCs. Although I'd much rather get a nice, uncropped composition with the bare lens, I enjoy the challenge of seeing if I can get an acceptable (for me) image with the stacked TCs when it's necessary to use the combination. This photo is from my Mountain Bluebird post. I set all PP adjustments to zero and converted the RAW image to a TIFF using Canon's DPP software. In PS, I enlarged the image to 100% view, cropped the head, and resized to the 720 pixel limit, saving at 100% quality. Camera settings were 7D, 500/4 + stacked 1.4x and 2xTCs, f13, 1/500s, ISO 800, +2/3 EC, equivalent FL of 1400mm (2240mm if you count 1.6 crop factor ).

Thanks for the info.... 2240mm is pretty serious and the quality held up impressively! What was your tripod/head setup for this?

I use a Markins M20 head on a Feisol 3342 carbon fiber tripod. Only had two of three leg sections extended out on the tripod.

In PS, I enlarged the image to 100% view, cropped the head, and resized to the 720 pixel limit, saving at 100% quality.

Well since you cropped the head and resized, the 100% view doesn't really matter in this case. How big was the crop before you resized it? (Just curious how many pixels of the original we're looking at here.)

David,
If my math is right, this is about 5% of the original frame (1167 x 778 pixel crop from original at 100% view).