[LRflex] Re: Summicron 50mm take apart?

  • From: Steve Lang <stevelang@xxxxxxxxx>
  • To: leicareflex@xxxxxxxxxxxxx
  • Date: Sun, 2 Aug 2009 18:32:13 -0700

Thanks everyone for the great suggestions. One last question regarding the
topic of manual focus on a Canon 1.6x SLR-
In further testing, what I have found is that the Canon 50mm f1.8 is
actually a pretty sharp lens even wide open, it and the 50mm Summicron R
perform similarly in resolution at f2 when both are manual focused with Live
View + magnification. But what I now see is that when using AF the camera
typically misfocuses by just a bit, so the resulting images you capture are
less than optimal. Stopped down the depth of field is larger and I imagine
this is much less an issue.

What I am wondering (and this will vary from person to person), is how good
I'll be able to focus with a focusing screen on my XSi (and perhaps that
Nikon magnifier). On a tripod, it's pretty easy to get tack sharp images
with Live View focusing, but this is not appropriate for all
subjects. Manual focus on my Rebel through the plain viewfinder is
completely hit-miss, because the viewfinder simply isn't large enough to
resolve optimal focus. So the 'resolution' of a focusing screen will be
somewhere in between those 2 extremes (as is the performance of the AF on my
Canon 50mm f1.8.) I'm just wondering where in between those extremes I
should expect to be.

I'm obsessing a bit about this, as I tend to do when choosing my equipment.
Of course in the long run, I'm not going to worry too much about this, and
just go out and have fun shooting. But it has been an interesting learning
experience as well- I always assumed that AF lenses focused pretty much spot
on, and in my observation it clearly may not.

Thanks,
Steve



On Sat, Aug 1, 2009 at 1:19 AM, Richard Ward <ilovaussiesheps@xxxxxxxxx>wrote:

> Hi Steve,
>    the 'viewfinder size' effect you commented upon between rebels and the
> 30D type Canon's is primarily due to the type of 'prism' is used to bring
> the lenses image up and around to the eyepiece you look through. The cheaper
> cameras use 'mirror prisms' and while it works, it usually gives a dimmer
> image and feels like you're looking into a tunnel. The more expensive slr's
> use real "glass type prisms" which usually run circles around the mirror
> kind if they're designed right.
>    The focusing screen is part of the "mirror" area you see when you're
> changing lenses. I am being intentionally vague here because I don't want to
> misdescribe something working from my usually shuffled memory files and
> either send you on a wrong tangent or embarrass myself!
>    Before you spend funds and muck around inside your camera I suggest
> physically seeing the kind of focus aid's film cameras all had once upon a
> time. A friend or relative might have one laying in a closet or you can
> fiddle one up for a tiny sum somewhere.
>    If you're loving the Manual Focus glass, I highly reccomend going with a
> replacement screen and will 100% do so myself, but I know what I'd gain,
> what I'd be using, how to use it, and the effects of losing the built in
> screen. ie: the etched af focus marks of the factory one (and if your's
> light up, they won't light up anymore). There can also be a need to
> compensate for certain metering problems - so I hear.
>
> Just make sure you're an informed consumer!
>
> Richard.
>
>

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