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From: ark@alice.UucP (Andrew Koenig)
Newsgroups: net.rec.photo
Subject: Re: How sharp are Minolta lenses
Message-ID: <4868@alice.UUCP>
Date: Thu, 23-Jan-86 13:53:39 EST
Article-I.D.: alice.4868
Posted: Thu Jan 23 13:53:39 1986
Date-Received: Fri, 24-Jan-86 09:34:44 EST
References: <2625@amdahl.UUCP>
Organization: Bell Labs, Murray Hill
Lines: 66

> But I digress.  What I would like to ask of the net is this:  Does
> anyone have data on the relative sharpness of the different Maxxum
> lenses?  As of now there are no aftermarket lenses, though I have
> heard this will change about April.  But for now, I need more than
> the 35-70 f/4 zoom that I bought with the body.  I talked with a
> local camera shop and they stated that the 50mm f/1.4 was *sharper*
> than the 50mm f/1.7 !!  And claimed the 24mm was the sharpest.
> The f/1.7 is about $58 and the f/1.4 is about $150 locally at
> discount stores.  Does the extra cash buy an all around superior
> product?

Sharpness isn't everything.

In practice, contrast may be more important.  Consider: the limiting
factor on sharpness with most hand-held photographs is camera motion,
even at 1/250 second.  The next limiting factor is often the quality
of the processing (if prints) or projector lens (if slides).

Just about any decent lens will deliver images nearly as sharp as the
film can handle if stopped down to f/8 or so.

However, lenses seem to vary greatly in contrast.  Factors that influence
contrast include the number of elements, the type and quality of the
lens coatings, the type and quality of optical glass used, and the
extent to which physical design has reduced internal reflections.

To convince yourself of this, take your camera outdoors on a sunny day.
Point the camera at a shady spot, in a position in which direct sunlight
can strike the lens but the sun is not visible in the finder -- not even
almost visible.  Look at the contrast in the image in the finder.  Now
hold your hand (or have a friend hold a hand) so that it casts a shadow
on the lens.  Since the sun isn't visible in the finder, the hand won't
be either.  But watch how much the contrast picks up!

Food for thought:

	All other things being equal, a lens with fewer elements will
	have less internal reflections than one with more elements.
	Unfortunately, all other things are rarely equal.

	Often the most important thing you can do to improve contrast
	is to use a lens hood.  A good one, designed for that particular
	lens.

	Keep your lens clean!

	If you use a filter over the lens to protect it, consider removing
	it.  It just introduces two more surfaces to generate reflections
	and degrade contrast.  In 20 years of 35mm photography, I have
	found that a good lens hood does a perfectly adequate job of
	protecting my lenses while I'm using them, and a lens cap does
	an excellent job when I'm not.

	While modern zoom lenses are as sharp as their fixed counterparts,
	they are often much less contrasty.

	If you are trying to choose between an f/1.7 and and f/1.4 lens,
	ask yourself whether you will often use the f/1.7 wide open.
	If so, go with the f/1.4.  The extra aperture will make it somewhat
	easier to focus in dim light, and the 1.4 is likely to be sharper
	than the 1.7 when both are used at 1.7.  On the other hand,
	faster lenses are often less contrasty than their slower counterparts
	when stopped down.  Not always, just often.

Perhaps your dealer will let you take one sample of each lens outside
for long enough to take a few pictures with it.