Malcolm Stewart wrote:
----- Original Message ----- From: "R.Sriram" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, February 25, 2004 1:30 AM
Subject: Re: EOS Question about primes
snip
The 50/1.4 is much better built than the 50/1.8-II, with a steel lens mount and distance scales as well. However my sample of the 50/1.4 had very bad barrel distortion which became worse when focused close, as a result I couldn't shoot *anything* which had straight lines near the edges of the frame. Others have reported better samples.
I'm not disputing your findings regarding distortion, but I don't understand the mechanism, and its variation from sample to sample. My understanding is that lens resolution is dependent on (very) accurate assembly of finely made parts, and that barrel (& pincushion) distortion is a design feature "left in" by the lens designer (so as to reduce other aberrations), and is affected by the relative position of the elements to the lens' optical centre and aperture mechanism. The EF 50 f1.4 is a relatively simple lens (compared to zooms, at least), so I would have expected that assembly sufficient to achieve decent resolution, would have automatically delivered the same barrel distortion from sample to sample. So far in my usage, I haven't noticed any distortion with my f1.4 nor f1.8, but I haven't gone out of my way to set up the tests to measure the effects. When I'm focusing close, I automatically reach for my 100 f2.8 macro USM which may have a bearing on what I see!
Yeah, me too, but when I want to travel light I leave my 100/2.8 USM at home and stick with a single prime... that's where the 50 comes in handy. Not sure how the lenses are manufactured, but I've seen so much sample variation that the above results are not surprising. When I mentioned to my friend about the distortion on my 50/1.4, he let me test his sample, and the distortion was much less. The photo.net review here also indicates large sample variations, with people reporting anything between zero and humongous distortions : http://www.photo.net/canon/50-1.4 * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
