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DPChallenge Forums >> Hardware and Software >> Canon 17-40MM f/4L
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04/24/2008 09:39:54 PM · #1
What is your opinion? I saw photographs of this lens and they are awesome! do you see any issue using this lens with 20D?

Thanks for your response!
04/24/2008 09:43:41 PM · #2
This is a very popular lens among Canon users and will work just fine on your 20D.
04/25/2008 12:48:44 PM · #3
This is a great lens, it basically lives on my 20D. Lens flair, vignetting, and distortion are handled well and it's reasonably sharp throughout the frame. It's been out for awhile now, so there should be plenty of reviews and sample images to peruse.

It's also quite respectable on the on the 5D, resulting in some very dramatic shots.
04/25/2008 01:03:34 PM · #4
it's a great lens. Build quality is awesome! Which i only understood the meaning of once i used it. It's great having a lens i don't mind using in the rain (it rains a lot where I live). I think 'reasonably sharp' is underselling it a bit. It's strength is that it's sharp across the frame all the way from F4 to F16. Diffraction doesn't really do much until you're at F22 and then it only suffers a slight amount. My old Tamron used to go crap after F11, the canon gets better.

I used to think it wasn't very good compared to my Tamron but it's better in every way I think after having it for 2 months- so much so I sold my Tamron 17-50 f/2.8 and stayed with the canon.

Basically, for the money, i'm not convinced you can find a better all rounder. And if you get bored of it, it will retain around 80% of it's value on the used market.

That red ring is highly sought after.
04/25/2008 02:20:29 PM · #5
Originally posted by Tez:

I think 'reasonably sharp' is underselling it a bit.


Hehe, I'm only comparing to the Canon 16-35mm f/2.8Mk2 and maybe the Zukio 21mm prime. :P

Tez is right though, the 17-40mm has superb optics at a great price. It was actually my first "L" lens and has since convinced me to replace most of my gear with their L-counterparts.
04/25/2008 02:34:31 PM · #6
Dang, did I shoot with a bad one or what? I've used a friend's on a couple of occasions and I simply could not tell all that much difference between it or any other lens I've used.

I was going to get one, then after using his, decided not too. Yet, I read these threads where everyone *loves* it and I'm wondering what I was doing wrong. ???
04/26/2008 09:05:20 AM · #7
it's pretty sharp in my opinion.
04/28/2008 06:24:34 PM · #8
Thanks for all feedback!

Though another question on the same line :)

specification says Diagonal Angle of View: "104° - 57° 30'"

does it have to do anything with full frame or 1.6 multiplier? :)

I mean if I put this lens on my 20D, will have same angles or different at 17mm or 40mm?
04/28/2008 07:48:57 PM · #9
Originally posted by pgirish007:

specification says Diagonal Angle of View: "104° - 57° 30'"

does it have to do anything with full frame or 1.6 multiplier? :)


you *do* have to compensate this for the crop factor:

- at 17mm, 77° diagonal coverage
- at 40mm, 37.5° diagonal coverage
04/28/2008 09:48:11 PM · #10
Originally posted by kirbic:

Originally posted by pgirish007:

specification says Diagonal Angle of View: "104° - 57° 30'"

does it have to do anything with full frame or 1.6 multiplier? :)


you *do* have to compensate this for the crop factor:

- at 17mm, 77° diagonal coverage
- at 40mm, 37.5° diagonal coverage


I am sorry but how did you calculate this? :)
04/28/2008 09:54:22 PM · #11
Originally posted by pgirish007:



I am sorry but how did you calculate this? :)


Here's the Excel formula:

=2*DEGREES(ATAN(SQRT(Vdim^2+Hdim^2)/(Focal_Length*2)))

Where:
Vdim = Height of Sensor, in mm
Hdim = Width of sensor, in mm
Focal_Length = Focal length of lens, in mm
04/29/2008 07:29:12 AM · #12
Originally posted by kirbic:

Originally posted by pgirish007:



I am sorry but how did you calculate this? :)


Here's the Excel formula:

=2*DEGREES(ATAN(SQRT(Vdim^2+Hdim^2)/(Focal_Length*2)))

Where:
Vdim = Height of Sensor, in mm
Hdim = Width of sensor, in mm
Focal_Length = Focal length of lens, in mm


woooo...high tech but interesting! Thanks!

If I apply above formula on 17-85mm IS lens then It looks like 17-40mm f/4 and 17-85mm f/4.5-5.6 IS USM Lens on 20D would have same diagonal angle view. does that mean that a wide angle lens and a standard zoom lens would have same view when taken at 17mm? and wide angle won't be that wide? :(

Message edited by author 2008-04-29 07:36:56.
04/29/2008 07:57:38 AM · #13
Originally posted by pgirish007:


If I apply above formula on 17-85mm IS lens then It looks like 17-40mm f/4 and 17-85mm f/4.5-5.6 IS USM Lens on 20D would have same diagonal angle view. does that mean that a wide angle lens and a standard zoom lens would have same view when taken at 17mm? and wide angle won't be that wide? :(


Yep, 17mm is 17mm... as long as the lens is rectilinear (straight lines stay straight vs. fisheye, where straight lines curve and circles stay circular). 17mm is about equivalent to 27mm on a 35mm frame, so yep, not all that wide. Wide enough, mind, but not *super* wide. I don't actually own a rectilinear lens wider than 24mm, and when I need a wider view I usually elect to stitch a pano.
BTW, the formula for fisheye angle of view:

=DEGREES(4*ASIN((SQRT(Hdim^2+Vdim^2))/(FL*4)))

You can use these formulae for any sensor size, just plug in the height and width in mm.
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