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04-16-2007, 02:21 AM   #1
Inactive Account

Join Date: Mar 2007
Location: Porto - Portugal
Posts: 29

Hi all Pentax friends.

My K10D arrived a few days ago and I'm just amazed and very happy with her.
I had the first proof of her "tank power" yesterday when she fall from a wall about 1,70 meters from the ground. She was inside a tinny and very soft "hama" bag and after a big scare she torn on ok and still fine.

I guess the kit lens is good, but I want to try a prime lens on it.
I researched the net and I found three brand of a lens that seems good to me. The Takumar, the Asahi Pentax and a Cosinon, all 1.4/50mm.
I guess that takumar and Pentax are almoust the same with diferent leters, but what is a Cosinon? Can it be identical to the pentax, better or worse?
The Cosinon is a K mount.
The Takumar is a M42, but I think that with a K adaptor I can use her in my K10D ..., Can't I???

I really need some help on this. I'm a kind of Asahi fundamentalist LOL, since I made my formation in photography with a K1000 and after I read the a bit of the story of Asahi Co, and now the Pentax..., What can I say...
I just love to belong to this minority and small group of Pentax owners.

Where I live (Portugal), You can see Canons and Nikons , lots and lots of them, but how proud I am when I take the K10 out and see many of them looking for the corner of the eye... LOL

Well..., sorry for this long text...
Thank you in advance for your attention.
Kind regards,
Palu Guimaraes

05-18-2008, 01:20 AM   #2
New Member

Join Date: May 2008
Location: south of Italy
Posts: 11
You can use any M42 lenses on your k10 with an adapter. Please note that there are two types of adapter, a good version that permit infinity focus and a cheaper version that don't allow the full use of the lenses.

The cosinon is hard to admit but will give better performance on an aps-c camera then the Pentax will do.
Cosninon original list price:59, Pentax original list price: 68

If You give a look at the MTF curves of the M1.4 and of the Cosinon 1.4 You will find the following average behavoire for the two lenses:

50mm f/1.4 @ 10lpm
Cosinon 83% (maximum on centre @87% lowest on extreme border @77%)
Pentax75% (maximum on middle @78% lowest on full centre and extreme borders @72%)

50mm f/1.4 @ 20lpm
Cosinon 61% (maximum middle @65% lowest on extreme border @57%)
Pentax53% (maximum on middle @60% lowest on extreme borders @42%)

50mm f/1.4 @ 40lpm
Cosinon 30% (maximum on middle @33% lowest on extreme border @27%)
Pentax23% (maximum on centre @30% lowest on extreme borders @12%)

Average values for 50mm @2.8

Cosinon 95% costant value
Pentax 93% (90 on borders)

Cosinon 84% costant value
Pentax 75% (60% on borders)

Cosinon 55% (40% on borders)
Pentax 43% (18% on borders)

Wish it helps...

The above values are valid only on APS-C Camera!!! Not on full frame

05-18-2008, 03:06 AM   #3
Senior Member

Join Date: Apr 2008
Location: UK
Posts: 167

One thing you might want to take into account is that the takumar will be fully manual, giving you more work to meter. I dont know about the Cosinon, but the Pentax comes also in A version (and F,M,K,FA) which is just as solid as M but allows for control of the aperture by the camera. This makes your life easier.

Fica bem, cumprimentos
05-18-2008, 03:51 AM   #4
New Member

Join Date: May 2008
Location: south of Italy
Posts: 11
The cosinon is a manual lens as the Pentax M, works fine in stop-down. I just bought one (not tried yet) from a man who doesn't know that on its k100D he can go in stop down with this lens, so he give it away...


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