EF 15mm Fisheye rectillinear conversion question

Hi all, this is my first post on this forum but I've been treating the Digital Picture website as holy doctrine for the last year or so, when it comes to selecting hardware.


Im looking to get a wide angle lens somewhere in the region of < £700 and am torn between the 17-40mm f4L and the 15mm fisheye


I use a Canon 5D mkII, so 15mm is gonna be very wide, also, with 21MP, cropping an image or squashing it slightly to compensate for rectillinear conversion isnt going to be a huge issue.


My question is aimed at anyone who has used the fisheye in this way...


... how much image quality is lost in this process? I would like to be able to use the fisheye as a standard ultra-wide angle (from time to time). But I want the images to still be of good enough quality to submit to high end stock sites.


I use Lightroom 3 and the lens profiles to do any lens correction


Thanks in advance for any input

incase anyone's interested...


I found a way to answer the question myself - just found an undistorted image from my collection and applied the 15mm profile to it


my conclusion; unacceptable quality loss (in the corners) unfortunately, even when you limit the distortion correction to 50%. The CA is hugely amplified and the image becomes VERY soft in the corners - this was starting with a Sigma 50mm f/1.4 set at f/11.


I think I'll be going with the 17-40mm, maybe get a dedicated fisheye further down the line

Hey and welcome!


A small tip: You could also take a look at the Sigma 12-24 which is practically the widest non-fisheye lens for FF out there I think.


There was a small new thread about it from Ben (btaylor), but I cannot find it anymore...perhaps due to the forumcrash last wednesday...


Good luck,


Jan

cheers jan, I did look at it briefly, however, I want to stick with Canon as this lens will finally allow me to qualify for CPS membership :D

If you correct a fish eye it will be 12mm cropped 2 to 3 aspect ratio. But the 12-24mm will be sharper, but you loss f/2.8. So it's a trade off.


John.

Quote:

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Originally Posted by markbarton

cheers jan, I did look at it briefly, however, I want to stick with Canon as this lens will finally allow me to qualify for CPS membership :D

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Alrighty then. I never really heard of that and I checked it out... looks interesting and I'm gonna have a look at it, thanks [:D]

thanks John


I'm still torn between the two lenses [:S]

I don't think you should be 'torn'. If your goal is to take some photos with 'the fisheye look' then get the 15mm fisheye. If your goal is a 'standard ultrawide angle' then get the 17-40mm. Converting fishsye to rectilinear results in substantial quality loss, especially corner softness. You stated, "I want the images to still be of good enough quality to submit to high end stock sites." - I think that pretty much rules out rectilinear correction of fisheye images.

hi neuroanatomist - the reason i'm torn is this...


ive heard a few reports of poor sharpness (especially in the corners) on the 17-40


also, because I mostly do nature photography - the fisheye effect might be less obvious in pictures I take that I want to remain "conventional" (very few straight lines - more abstract shapes) do you get what I mean?


I havent had a chance to play with one myself (17-40) but will try to borrow one before I decide

Quote:

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Originally Posted by markbarton

ive heard a few reports of poor sharpness (especially in the corners) on the 17-40

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The rumors are true if you shoot wide open, but it becomes very sharp as you stop down. I use it at f/11 on my 5D2 and it's excellent.

ah, thats good to know - amost all the reviews Ive found only look at the performance on a cropped frame or on an older, low res sensor


if it looks good on a 5D2 it'll look good on anything I guess!

Quote:

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Originally Posted by markbarton

also, because I mostly do nature photography - the fisheye effect might be less obvious in pictures I take that I want to remain "conventional" (very few straight lines - more abstract shapes) do you get what I mean?

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You don't want a horizon in your shot unless you want to make smiley photographs [;)]



<div>

Quote:

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Originally Posted by markbarton

ah, thats good to know - amost all the reviews Ive found only look at the performance on a cropped frame or on an older, low res sensor


if it looks good on a 5D2 it'll look good on anything I guess!

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<div>On a 5D2 I also experience very soft extreme corners wide open, but good centre-sharpness.</div>
<div>If you want a good view and shots from multiple users and subjects: pixel-peeperI made sure the photos you see are full size 21mp photos from a 5D2 with a 17-40L at 17mm f4 wide open. You can change your search-criteria as you like.</div>
<div>And a link to some sharpness analysis: photozone-fullframe test</div>
<div></div>
<div>Good luck!</div>
<div>Jan</div>
<div></div>
</div>

thanks for those link Jan, they were very helpful


I've actually tracked down a friend who has this lens - gonna take some tests of my own tomorrow :)

That's great Mark, glad I could be of any help.


Hope to see some more of your photos. I like them [Y]

cheers :D


plenty more on my website if you're interested...


www.markbarton.co.uk

Thanks, I had seen them already[;)] I see you've met Sean's aunt Edna as well [A]


I like your site: simple and straight forward. If I may give you a tip...try to make some "home" or "back" buttons so you can get to your homepage again after viewing your pages.(about/gallery/blog/projects)

Cheers Sheiky :)





oh, and for anyone who is interested to hear the thrilling conclusion...


I tested my friends 17-40mm and found the performance to be unsatisfactory. Below are some sample images of the worst case scenario - 17mm f/4.0 at ISO 200 (5D MKII). Unfortunately the corner sharpness does not improve much with stopping down, even at f/11 it was unacceptable :( CA was also quite bad at the wide end. The lens performed very well on the long end, but that isn't what I'm buying it for, I want a wide angle lens for landscapes...


Anyway, here they are, the first image is straight out of the camera - no sharpening or noise reduction, the second image has has Canon's lens profile applied to it and has noticeably less CA.


http://www.markbarton.co.uk/Uncorrected.jpg


http://www.markbarton.co.uk/Corrected.jpg

I see pretty much the same result as I had while testing the 17-40. Extremely soft extreme corners. The Sigma 12-24 is definitely better in this regard, but it wouldn't give you a CPS membership...


I guess you have to keep on saving for a good prime(TS-E perhaps) or for the 16-35L


Thanks for the conclusion!