timballic Offline Upload & Sell: Off
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Rebought an EF 17-40/4 (like new) to try on the IR A7, and compare with some primes in the range.
First with the Tokina RMC 17/3.5, PK mount(a nice copy) On KolariVision's "Good for IR" list
Both using Kipon Adapters. On the colour A7 camera, both lenses checked out as well centred copies.
I think the adage, that if a lens has weaknesses, they will be magnified in IR, really shows true for the EF 17-40 here.
Hot-spot patterns slightly with each: I'll upload the F/8 results as that's where I'd use them. This is probably a worst case, as the sun isn't far out of the right of frame and both needed careful flagging to prevent multiple flares, the EF zoom is particularly prone to them.
First the Tokina:
Tok RMC 17/3.5 @8 by Timothy Ball, on Flickr
Now the EF zoom:
EF 17-40 @17/8 by Timothy Ball, on Flickr
Slightly more "patterns" with the Tokina, but also slightly lower contrast on the EF zoom, which surprises me.
It would be easier to hide the more diffuse EF patterns in pp, than the Tokina patterns, but neither are bad.
An "overall shot", again F/8 (Full size files in Flickr link) Less than 2mins between series, but those clouds were racing! Both focussed on the sharp corner of the concrete tub to right of centre foreground. (I tried a refocus with the zoom, because of the poor corners, but these were the best I could get them. NB. If I focussed just for the near lower corners, I can improve them slightly, but then lose the necessary depth of field.)
First the Tokina:
Tok RMC 17/3.5 @8 by Timothy Ball, on Flickr
The EF Zoom:
EF 17-40 @17/8 by Timothy Ball, on Flickr
Now the lower corners from each 1:1
L. Left, Tokina
L. Left Tok RMC 17 @8 by Timothy Ball, on Flickr
L. Left EF Zoom
L. Left EF 17-40 @17/8 by Timothy Ball, on Flickr
L. Rt Tokina
L. Rt TokRMC 17 @8 by Timothy Ball, on Flickr
L. Rt. EF Zoom
L. Rt EF 17-40 @17/8 by Timothy Ball, on Flickr
Comments: In use the Tokina is obviously smaller and lighter at 312g, than the EF 17-40 at 520g, but then the zoom replaces several lenses.
The EF 17-40 is easy to focus manually and the image snaps in and out of focus at F/4, the Tokina is soft and diffuse at F/3.5 making wide open focussing difficult, but a ½ stop down, it sharpens up nicely.
At F/8 where I'd use them, the EF Zoom is perhaps a tad clearer, but not a lot in it, both similar sharpness in centre, but the corners (and to a less extent, edges), are where the difference is revealed. I remember that on my old 5DII, the zoom at 17mm had poor corners, on the A7 and in IR, they're MUCH worse. The Tokina is better, still only "adequate", but a lot better than the zoom. (Look at the foliage under the front of the mini.)
Overall: it could be a case of, 6 of one, half a dozen of the other:
Hot spot flare patterns are slightly present on both.
Focussing the EF Zoom is easy (manual), the Tokina needs to be stopped down a little to sharpen up and never seems as positive as the zoom.
The corners are the real issue. I could "just" accept the Tokina corners, the EF 17-40 corners are very, very poor, (on the A7)
Then of course the EF 17-40mm covers 3-4 prime focal lengths, if you use 17mm, 20mm 24mm, 28mm 40mm
However, the corners really don't become "acceptable" until 28mm, and I think that will be the clincher for me.
I'm sure that on a FF Canon IR converted camera they'd be a lot better, if never exactly good. When I owned this lens I had an IR converted 40D which being apsc, never showed into the corners.
I'm hoping to compare the EF 17-40/4, with Nik Ai 20/3.5 and Pentax SMC M 20/4 next, having discounted the CV 20/3.5, NAiS 20/2.8 and OM Z 21/3.5 MC, because of their bad hot-spot characteristics. (Really not sure whether to try a single coated copy of the OM Z 21/3.5)
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