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Three 105's compared
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PostPosted: Wed Mar 11, 2009 10:44 am    Post subject: Three 105's compared Reply with quote

I thought I'd compare a SMC Takumar 105mm f/2.8, a Soligor T4 mount 105/2.8, and for fun, a SMC Takumar 50/1.4 with a generic 2x tele converter.

Much to my surprise the Soligor walked away with the prize, at least among my samples of the lenses. Production and life time experience will make every lens somewhat different. The Tak 105 I'd bought from Eric Henderson, so it should be in good condition though.

The 50 + converter pics are invariably warmer than with the other two lenses - this probably the effect of remaining yellowing in the 50/1.4. The combo got reasonably good results closed down, and at the wider openings gave a nice vintage glow look that can be useful.

The shots are all Av mode, +2 EV, AWB, K100D. Oh, and I focused, with the confirmation light lit, on the back wall, so the rail and chair are in front of the focus plane. Not ideal, but more interesting than showing the wall. In retrospect, I'd put the chair or something in the center to focus on. However, the results are similar when I did a different series of comparisons on a central object surrounded by distant objects.


Soligor 105 at f/8


Takumar 105 at f/11


Tak 50 + 2x converter at f/4


Lens order in crops: Soligor, Tak105, Tak50+2x
100% crops at f/2.8


100% crops at f/4


100% crops at f/11


JPEG file sizes:
Soligor 105:
f2.8 = 2.14mb, f4 = 2.33mb, f5.6 = 2.58mb, f8 = 2.60mb, f11 = 2.47mb
Tak 105:
f2.8 = 1.91mb, f4 = 2.15mb, f5.6 = 2.37mb, f8 = 2.3mb, f11 = 2.52 mb
Tak 50 +TC
f2.8 = 1.75mb, f4 = 1.88mb, f5.6 = 2.04mb, f8 = 2.18mb, f11 = 2.42mb

(click on images to get to the flickr pages, where full size versions of the 100% crops is available)


PostPosted: Wed Mar 11, 2009 11:18 am    Post subject: Reply with quote

I think it's obvious that the Takumar was focused on a different point. This is not lens softness but OOF softness. You can actually see it in the windows: the left windows of the Tak are sharper than the Soligor windows... So, the focus plane is different I think.


PostPosted: Wed Mar 11, 2009 11:26 am    Post subject: Reply with quote

I don't find where the soligor was focused.

Anyway, the tak 105 is a great lens, and this test shows it clearly.


PostPosted: Wed Mar 11, 2009 2:37 pm    Post subject: Reply with quote

As I explain in the text - for all three I focused on the center of the frame, i.e. the back wall, so that the focus confirm light in the K100D was lit. This however could produce a difference in absolute focus - I agree the Tak 105 is probably focused further out than the Soligor. They were all a smidge short of infinity in this shot.

But similarly, you can look at the back wall in each case.

With digital crop cameras, this focus issue can be thorny indeed.

My main objective was met however - seems to me the Soligor is at least the equivalent to the SMC Takumar.

And the 50 + 2x is a useful tool for special effects.


PostPosted: Wed Mar 11, 2009 2:53 pm    Post subject: Reply with quote

Nesster wrote:
As I explain in the text - for all three I focused on the center of the frame, i.e. the back wall, so that the focus confirm light in the K100D was lit.


And that's where the problem may lie: in my experience, the focus confirmation of our Pentaxes with MF lenses leaves (at least to me!) a lot to be desired. Especially with subjects further away it's almost impossible to have two cameras focus on exactly the same subject. Live View helps a lot here, but the K20D's live view is very mediocre at best, and your K100D cannot do it.

Thanks for the tests, however!


PostPosted: Wed Mar 11, 2009 5:03 pm    Post subject: Reply with quote

Ditto on the focus issue, even if the focas plane or object selected is the same, the Pentax focus confirm works across a range of values for "focused", and you can get different focus points on several attempts even if everything else is constant. Thats why I try to bracket focus.

I think the same problem exists with other focus confirm systems, the confirm logic (and autofocus logic) has to work on the basis of "good enough" rather than "perfect", otherwise the thing may hunt forever.

In any case, the Takumar 105 seems to have better contrast than the Soligor, though its probably going to be difficult to judge them on sharpness. The Soligor may be sharper indeed.

I have the Vivitar version of the T4 105, which seems to be the same Tokina lens, and I find it very sharp.


PostPosted: Wed Mar 11, 2009 5:57 pm    Post subject: Reply with quote

I'd agree!

I have a split image wedge on my K10D and when it shows sharp, the confirm light does not - and the other way around.. as I said in a previous post, I tried out the F4 SELF-autofocus (i.e. the lens itself does the focus thing using built-in mechanism irrespective of the camera used) Tamron Adaptall-2 70-210 lens I got from DOF - and when it said it was sharp, it agreed with the wedge, not the MF confirm lamp - so it would appear that there is a generic problem here?

Odd as I said, how an autofocus lens has rescued a manual focus fanatic lol

Could the wedge upset the AF on the Pentax? I might try and replace the original plain glass screen - but that looked sharp no matter what, on most MF lenses!

Doug.



Spotmatic wrote:
Nesster wrote:
As I explain in the text - for all three I focused on the center of the frame, i.e. the back wall, so that the focus confirm light in the K100D was lit.


And that's where the problem may lie: in my experience, the focus confirmation of our Pentaxes with MF lenses leaves (at least to me!) a lot to be desired. Especially with subjects further away it's almost impossible to have two cameras focus on exactly the same subject. Live View helps a lot here, but the K20D's live view is very mediocre at best, and your K100D cannot do it.

Thanks for the tests, however!


PostPosted: Wed Mar 11, 2009 7:25 pm    Post subject: Reply with quote

Thank you all - I was debating whether to post these due to the problems, but I'm glad I did. Lots of good info in the discussion, you guys are great!


PostPosted: Wed Mar 11, 2009 10:59 pm    Post subject: Reply with quote

nemesis101 wrote:
Could the wedge upset the AF on the Pentax? I might try and replace the original plain glass screen - but that looked sharp no matter what, on most MF lenses!

This isn't the first time I've read this, but I find the screen on mine snaps into and out of focus very well, even in room lighting. Double checking it with the confirm light, it's always backed up exactly (well, as exactly as reasonable for one of these). I suspect the PO set this camera up or had Pentax or somebody who knew about them do it properly. Otoh, maybe I've just been lucky with the lenses I've used on it so far... Smile


PostPosted: Thu Mar 12, 2009 10:08 am    Post subject: Reply with quote

I do have the regular screen for my k10D and have the same problem. When I see it as sharp, the AF-confirm light doesn't.
If I go by the assist, pictures will not be focussed correctly.

/ Jan


PostPosted: Thu Mar 12, 2009 10:57 am    Post subject: Reply with quote

Here's one sample of the other comparison I did, at f/5.6, the focus match is a bit better (though I think the Tak is a bit further back focused than the Soligor), but the exposures aren't precisely the same...

Gives a better feel for the Soligor/Tokina cool tone vs. Takumar, and shows the two lenses about equal, in my eyes anyway.



Click on pic to go to flickr where a 100% size - actual pixels, no post processing - is available for those interested in peeping.


PostPosted: Thu Mar 12, 2009 11:04 am    Post subject: Reply with quote

nemesis101 wrote:
Could the wedge upset the AF on the Pentax?


No; the viewfinder has nothing to do with the AF function as the sensor is located below the mirror. So even if you take out the ground glass screen the camera will still do AF.