How do I test and compare lenses

Hello,

Yesterday, after a long wait (US to India by regular mail), I received
my M42-to-EOS adapter that I had ordered for $12.95 from eBay.

I immiediately set upon comparing the kit lens (Canon 18-55mm) with the
Pentax Super Takumar 50mm f/1.4 on my Canon 300D.

First, I mounted the camera on a tripod, secured all the screws, set
the camera to "M" mode and went about shooting a fixed subject indoors.
Once I set the focus, all I did was change aperture values for each
successive test shot to compare the difference between various f-stops
of the lens. I also used timer and MLU.

The images at 1.4 are horribly unsharp. Sharpness started picking up at
f4, was best at f5.6-f10 and was reasonable at f16.

I compared the kit lens at 50mm f/5.6 to the Pentax 50mm at f/5.6.
Results were not very different.

But somehow the horrible unsharpness at f/1.4 and the little difference
in results between the kit lens and the Pentax 50mm left me thinking if
I've been doing something wrong in the testing.

Other than that the Pentax's focussing ring is damn smooth. Once I went
back to the kit lens I was *shocked* by the jerky and wobbly focus
ring. Metering wasn't tough either with the Pentax. In "M" mode, I just
made sure than the adjustments to the shutter speed kept the exposure
indicator at "0".

Suggestions/pointers appreciated.

- Siddhartha

Isn't there a mount to be removed from some lenses before it is fixed to the
adaptor? I'm not suggesting that you immediately start dismantling your
lens, but I seem remember having to do that once a long time ago with an M42
screw lens on a Russian camera, NOT a Pentax.

teflon wrote:
Isn't there a mount to be removed from some lenses before it is fixed
to the
adaptor? I'm not suggesting that you immediately start dismantling
your
lens, but I seem remember having to do that once a long time ago with
an M42
screw lens on a Russian camera, NOT a Pentax.

No, I didn't have to remove any part of the Pentax lens to make it fit
the M42-to-EOS adaptor. Although, I have also read about ring adaptors
that require part of the screw mount lens to removed before use but
haven't come across one.

I will also receive two more M42 lens sometime this month so will
confirm their usage as well.

- Siddhartha

"teflon" wrote in message
...
Isn't there a mount to be removed from some lenses before it is fixed to
the
adaptor? I'm not suggesting that you immediately start dismantling your
lens, but I seem remember having to do that once a long time ago with an
M42
screw lens on a Russian camera, NOT a Pentax.

That was probably a T-mount lens. They had a threaded adapter that was
similar in size, but a slightly different thread pitch.

"Siddhartha Jain" wrote in
oups.com:

But somehow the horrible unsharpness at f/1.4 and the little difference
in results between the kit lens and the Pentax 50mm left me thinking if
I've been doing something wrong in the testing.


The reason to buy the f/1.4 lens is to obtain f/1.4, not to obtain
sharpness at f/1.4. Your results sound pretty much like what I would
expect.

Bob

--
Delete the inverse SPAM to reply

"Siddhartha Jain" wrote in message
oups.com...


Suggestions/pointers appreciated.


1: There is always the possibility that the adapter that you bought may be
throwing things off. If you could get your hands on an Asahi Pentax screw
mount camera, and conduct the tests using that, you might obtain improved
results, in which case I would recommend that you obtain a genuine Asahi
adapter, rather than an aftermarket one.

2: Your lens might be defective. Takumar lenses are well known for their
sharpness, contrast and build quality. See:
http://www.luminous-landscape.com/co...02-11-24.shtml

3: SMC Takumar lenses were tested by Popular Photography Magazine, and the
Takumars tested sharper than the Leica lenses. Your test results are
clearly out of line with the conventional wisdom regarding Takumar lenses.

See: http://medfmt.8k.com/mf/rangefinder.html#keppler

I really question the wisdom of testing a screwmount lens on a camera that
uses another lens mount. If anything, your tests just might reveal that the
use of aftermarket adapters may adversely affect lens sharpness.

In article .com,
Siddhartha Jain wrote:

But somehow the horrible unsharpness at f/1.4 and the little difference
in results between the kit lens and the Pentax 50mm left me thinking if
I've been doing something wrong in the testing.

If a 50mm Takumar is taking "horribly unsharp" pictures, it's either
broken or you're doing something wrong. Note that it can be very
difficult to manually focus most autofocus bodies. On the other hand,
you also say the Takumar is giving results similar to the kit lens -
which should be at least decent. Just how bad ARE your results?

Other than that the Pentax's focussing ring is damn smooth. Once I went
back to the kit lens I was *shocked* by the jerky and wobbly focus
ring.

Completely normal, if unnerving. AF lenses are built to be focused with
a minumum of movement and force, because of the tiny motors that
usually do the focusing. Inside you'll find wide pitched, plastic rings
with a minimum of lubricant. MF lenses can be MUCH more precisely made,
with a fine metal helicoid and thick grease.

Scott Schuckert wrote:
Just how bad ARE your results?

http://www.geocities.com/losttoy2000...ax-resize.html

http://www.geocities.com/losttoy2000...ntax-crop.html

Unfortunately, I seem to have hit the data transfer limit on geocities


Well, the horrible results are at f/1.4 only and not at other
apertures, so could something still be wrong with the lens?

Funnily, in the f/1.4 image, the part around the centre is a bit more
sharper than the centre itself!!
I am more inclined to think that I goofed up somewhere.

- Siddhartha

Siddhartha Jain wrote:
Unfortunately, I seem to have hit the data transfer limit on
geocities


Fixed. Now at fortunecity as well.

http://members.fortunecity.com/lostt...ax-resize.html
http://members.fortunecity.com/losttoy/pentax-crop.html

Siddhartha Jain wrote:
Unfortunately, I seem to have hit the data transfer limit on
geocities


Fixed. Now at fortunecity as well.

http://members.fortunecity.com/lostt...ax-resize.html
http://members.fortunecity.com/losttoy/pentax-crop.html