Hi,
Good, it seems we've got some discussion going on this topic. Here's a bit
more input from me:
[C.H.Ling]
Testing at 5m is not enough, at least you should test it at infinity
too. Pop photo also test lenses at closest distance, in most case the
distortion is much higher.
Hmmm, the closest distance test should be possible, but the infinity one
might be a bit more complicated, i.e. it may be a bit difficult to find
something like a brick wall that's big enough to fill the full frame when
using the lens @35mm at the infinity setting...
Do these two settings really influence the distortion heavily? If so, our
tests may be void again. Oh well, as mentioned previously, for me the most
interesting part of these tests is to have an indication of how badly the
distortion shows; I guess I'll be satisfied with a less-than-perfect
test...:/
[Joel Wilcox]
I agree. I don't expect to find something different from Gary's results.
I'm just interested in how those results may affect my photography and what
I may wish to do about it.
Exactly, that's my idea too.
Olaf, I shot at f8, rather than f5.6, sorry.
From what I've understood from Erwin, the aperture used shouldn't have any
effect on the distortion. I chose f5.6 because that is the biggest aperture
setting which all lenses that I tested have in common :)
I shot at approximately 4-5 m.
That should be fine. I can measure the distance I more or less shot at, but
I estimate it to be some 5m.
I painstakingly tried to get the camera square to the wall. This may seem a
little comical. [...] Was there an easier way to do this?
Hmmm, good question, as I was 5m away from the wall, I didn't go out of my
way to get the camera 100 0n parallel to the wall, but rather I was
satisfied with getting it pretty parallel to the wall. I did give this some
attention, but I didn't use such a method... No idea if there are easier
reliable methods :)
Using an adapter, I mounted my spirit level on a Bogen QR plate and leveled
the tripod. I noticed that I got a different reading when I put the spirit
level in the shoe of my OM-4. So I have to assume that the shoe is not
perfectly parallel to the base of the camera. I checked my other bodies
and only a OM-2S that John H. CLA'ed in the last couple of years is really
level. So if you use a spirit level in the shoe, you might want to
ascertain where level really is with your camera.
The Manfrotto tripod I used has 4 levels incorporated in it. Out of these 4,
3 of them are featured in the head, and these are the ones I used for
leveling the camera. I cannot be 100 ertain that the camera itself was
absolutely level then, but as this is a $400-$500 tripod, I guess (hope) I
came close enough. Actually I'm glad I could borrow this tripod for this
test, as my own tripod is a simple lightweight video tripod (with weight
being the keyfactor for selecting it), which only has one simple level in
it.
A funny thing to notice, BTW, is that when looking through the viewfinder
all lines seem to be nicely straight, and I couldn't detect any distortion
with any of the lenses this way. Nonetheless, I'm positive the distortion
will show up in the end results. Does anyone know why this appears to be the
case, or was I perhaps drunk in such a way that the bent lines appeared
straight to me ?!? ;)
[Gary Reese]
Hopefully there would be space in an OM Book to show what kind of
distortion a statement like "pronounded barrel" etc. really means.
That's certainly an interesting idea! If anyone wants to use my images for
the book, please let me know and I shall grant permission to do so.
Actually, I would have loved to contribute something to the book, but
unfortunately I can't seem to find the time to do so...:(
I hope the progress is going well though, and perhaps in the future I might
be able to contribute to the book...
[George S]
correct. Even the ads and specifications for Zeiss optics mention that
"distortion has been reduced" or "distortion has been minimised". It
(distortion) - at some level WILL be there....how noticeable... well...
that's the $64,000 question...
Indeed, and that's exactly the reason why I'd like to see how badly the
distortion influences the end results :)
[Erwin Voogt]
For me, the idea was to see if I should avoid the 35-80/2.8
at its 35mm setting for critical pictures,
!!! Funny, we are talking here about a $1000 lens...
Yes we are. And to draw an analogy: would you want to use a $200,000 Ferrari
in city traffic and traffic jams? IOW: no matter how expensive something may
be, it may have its "flaws" (or at least disadvantages) under certain
circumstances. So, even though it sucks that such flaws/disadvantages exist,
it's best to learn to live with it, and if an easy workaround (like using
the 35/2.8 Shift which I already happen to have where the lenses are
concerned) can be had, why not use it for the critical work around 35mm?
Now, since I do live in the centre of a city, my sole reason for not having
a Ferrari is my bicycle workaround of course ;)))
I did make some brick wall pictures with the Tokina ATX. They look very
good and you can use this $200 lens for critical pictures... ;->
In about a month I will get a new computer, so I will be able to scan
slides again.
Yes, it should be good to see these results too. Did you actually also test
the lens around 40mm and at the 70mm setting? If not, would you please do
this too, so we can see if the lens has little distortion at these focal
length settings too?
Cheers!
Olafo
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