I used and ext 2Xiii with a 550D and Ef 300f 2.8 is .then same combo with a 1Div.then 1div 2xext iii and fiinally where I am now 1dxmark ii ext iii actulaly use both 1.4 and 2X and a 400DOii
you MFA micro focus adjust ( if the 90D allows) that's your first step. In all the above incarnates the 1.4 gives slightly better IQ than the 2x,,,,,,............but one can work on that in post
What is much harder to work with is the AF especially with a moving subject...............................Noel with my 550D it just didn't have the grunt the sheer batterypower to move Af fast but with the wind in an owls face to SLOW it and me physically taking to the combo common focus please focus.iit's doable
an old image bro and probably more to be had given my learning curve and help with PP
IMG_0312 by
Stuart Philpott, on Flickr
Mate the above isn't furpect it's meant only as an example of whats poss with a small camera body driving a big lens.
When I stepped up to the 1Div Af got better,,,,,,honestly I'm unsure on IQ I wouldn't say I was hit by a step up in IQ
Same really when I stepped up to the 400 DO ii..........the 300F 2.8 is one hell of a lens as is the IS ii,so sharp ya can cut yourself the DO is also up there
Adding that last chink a camera body designed to work with EXTiii's to lens designed to work with EXTiii's was where the combo started to sing
all failings now became mine
Noel this is a 400DO image on the mark vi and incidentally 1.4 ext............ IQ isn't deparately different to the 2X and smaller body but Af is....plus the fact I was able to move the DOii VERY fast 'cause it's light..but back to ext's IQ not a huge upgrade AF is monster I cannot stress how much AF has changed here
_70F4463 by
Stuart Philpott, on Flickr
honestly I doubt Ii'd have got focus with the 2X though,the above spar is screaming down a hedge it's just one of those on the edge piccies ya don't oft get
So my humble thoughts are thus.canon EXT iii's are one of the biggest bangs for the buck you will get from canon, IF you need reach. go buy your EXT's actually both
If you pair to a body and lens that canon designed to work together man they work
You are not repeat not going to get the best with a 90D..that said it is not undoable utterly not unuseable
You work with the tools you have mate, get your Ss high enough to freeze motion make sure the combo properly is as near bang on with regards to focus as you can.......IE MFA
Next is way too big a crop at 800mm IE the doii the EXT 2xiii and the DXii
_S2I3428 wing flip smj tdn add c by
Stuart Philpott, on Flickr
Noel I hope it's ok posting my efforts on your thread.to me it is easy to waffle on stuff I just thought if you had comparisons with camera bodies exts and the same guy shooting with ALL his failings,
it might help more than just words
Oh and I am not a raptor nut barely shoot BIF, but ya know we pays are money and takes our chances
Go buy your 2Xiii learn about it's short comings with the gear ya have now, learn how post can help buy a 1.4 too and get the combo pin sharp on somethiing static via MFA. a brick wall with a marker on is a good start...one can go further with gizmos.
Just a bit more on MFA......your camera is built with a tolerence so is lens and body,all can be plus or minus by a little tiny bit.you marry them so they work as a team
all the luck
stu