-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Ken Durling
Sent: Thursday, May 31, 2001 7:33 AM
To: [EMAIL PROTECTED]
Subject: Re: EOS Single lens for travel
My 28-135 has much less barrel distortion than the 28-90 - at 28mm,
although it is there.
Is it possible to make a 28mm without barrel distortion??
Ken Durling
Hi Ken,
Yes, the EF primes and the EF 28-70 2.8L have much lower barrel distortion
and are sharper in the corners with much better contrast overall and MUCH
lower vigneting than the EF 28-135IS. When I mentioned that the EF 28-135IS
was soft at the long end I failed to mention barrel distortion in this lens.
When the EF 28-135IS came out I tested two samples from different stores
aganst each other and an EF 28-105USM (turns out this was an exceptionally
good very low serial number EF 28-105USM, I shoud not have sold it!). The
first EF 28-135IS I tried was when they FIRST came out in L.A. but the
results surprised and disapointed me so several months (6 or 7), later I
re-tested another lens and got similar results.
I used an EF 20 2.8USM as the standard for sharpness and distortion on the
short end, an EF 50 1.4L for the middle and EF 300 2.8USM at the long end as
my standards for image quality. I used Kodak ISO 100 Ektachrome film
processed by A&I in L.A. (one of the best in the contry), for comparison of
the images. I use positive films for lens testing for a reason, the same
ones pros used to use. This is a FIRST generation image and you can see all
the little gotchas without the additional problems of poor print focus,
additional image distortions (YES it's true!), added by printer optics and
color correction not to mention the variable of chemical and paper batches
varibles in machines etc.. The nature of second generation images is
distortion and varibles beyond anyones control.
O.K., so obviously the primes I used are were going to be a lot harder to
match than zooms (I should'a/could'a tested my EF 85 1.8USM but I got lazy,
this stuff takes a LOT of time to do this all carefully!), and while I have
EF 20-35 3.5/4.5USM, EF 28-70 2.8L and EF 70-200 2.8L zooms, I wanted to see
how the EF 28-135IS and EF 20-105USM compared with each other and with the
best of the primes.
Both of the EF 28-135IS lenses at the long end (135mm), were softer than the
EF 28-105USM (at 105mm), and there was more barrel distortion in the EF
28-135IS and a noticably lower contrast image on my chromes. Compared with
the EF 300 2.8L the both the EF 28-105USM and EF 28-135IS are very soft, but
the EF 28-105USM definetly had a visable edge over the EF 28-135IS at max.
focal length and wide open. Stopped down for f/8 they are very close but
contrast is still lower on the EF 28-135IS than the EF 28-105USM and of
course the EF 300 2.8L is the very clear winner at the f/stop on all
caounts. There also seems to be some variability of sharpness at differing
distances though I didn't go into it at the time it's interesting. The
images I used for comparason were all at shot with focus set to infinity,
wide open and at f/8.
In the middle range compared to the EF 50 f/1.4 the EF 28-105USM and EF
28-135IS are close both wide open and at f/8 except for the contrast loss
and slower lens speed of the EF 28-135IS. I shot the EF 50 1.4USM at the
same f/stop as the zooms wide open and again at f/8 to compare apple to
apples so to speak. In retrospect I wish I'd taken the time to shoot it
wide open too.
On the short end the EF 28-135IS and EF 28-105USM are not great at all
compared to the EF 20 2.8USM. The problem is a combination of distortion,
lower contrast, sharpness and light fall off in the corners. Distortion is
the reason I bought an EF 20 2.8USM, the discovery that contrast, sharpness
and light fall off was so much lower than the EF 20-35 3.5/4.5USM I had was
a major surprise for me. The EF 28-105USM fairs slightly better than the EF
28-135IS in contrast and distortion but sharpness and corner fall of is
about the same. Again I used the same focus at infinty and as wide as the
lens goes and at f/8.
This was my personal testing and it may seem unfair to some but it's the
straight stuff and are my own standards YMMV. I've done it a few times for
various lenses, this and other tests like it are what form my opinions of
image quality of the particular lens I've tested. This is not to say that
image sharpness is all there is to it but IMO this is a good start. If you
want the image to be sharp and have impact you must have a lens that can
deliver it if you do your part. If you WANT a fuzzy or distorted image on
film use a filter. Start with the BEST image you can get and go from there.
If you ask a lens with lower contrast and fuzzy corners with light fall to
deliver you will be disappointed, they just cannot deliver what you need.
Of course in this day and age of computers and digital images nobody seems
to be willing to pay for the difference or care to see the difference. This
is true in commercal photography as well, cheaper is better if images are
O.K. not great, even more true actually.
O.K. long enough rant sorry for the disturbance.
Regards,
Chip Louie
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