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05-20-2011, 03:53 PM   #1
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confused about lenses - still!

I've read a lot of good information on lenses, and I at least know now that what I'd like is to get a decent prime lens. I also am trying to find something that is 2nd hand but everywhere I look - it seems even 2nd hand Pentax glass is expensive. Ideally I'd like to try to find something for under $100. I want something fast that works great in low light - I've been looking at some of the Tamron and Pentax 40 - 50 mm F 1.4 - 1.8 lenses and am thinking any of those will probably work great for what I want. However, what I am a little confused about are the different kinds of mounts and the features and options that are available with each mount. There are screw mount lenses, some mounts that include auto focus capabilities, others that are just manual, and there's the whole aperture ring thing----what is that?? What's it for? Why would I want a lens with an aperture ring? Why would I want one without an aperture ring?

05-20-2011, 04:31 PM   #2
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Aperture rings usually come on lenses that only manual focus, but they come on AF lenses as well. In most AF lenses, the body will allow you to digitally control the aperture, but the ring allows for manual control over the aperture. You just turn the ring and the aperture changes sizes. The F number doesn't appear on the LCD screen.

Screw mount lenses are old lenses that requires a M42-K mount to attach to the newer DSLR's. They are manual focus.
Manual focus lenses with "M"or K like SMC-M have the aperature ring and exposure is all manual meaning you set the aperture, shutter speed, and iso.
Lenses with "A" can work on all exposure modes and is manual focus as well.
Newer ones labeled F, FA, DA, are auto focus and can work on all exposure modes. No need to manual expose.
05-20-2011, 04:40 PM   #3
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QuoteOriginally posted by slr_neophyte Quote
What's it for? Why would I want a lens with an aperture ring? Why would I want one without an aperture ring?
Short answer? Film.


Also cause the FA 50/1.4 happens to rock. No longer the best bang for buck on the market, but still worth it.

(If that's you in that shot and you don't want it to be a 50ish in particular, check out the new 35/2.4. )
05-20-2011, 04:49 PM   #4
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Pentax mount is K mount. Subsequent versions include KA (auto aperture setting), KAF (auto focus), KAF2 (SDM - silent auto focus). Since the camera body can control the aperture, that makes the aperture ring redundant. That's why the new lenses such as DA version no longer has aperture rings.

Aperture ring is to control the opening of aperture to let light in.

As a start, you should read the following websites:
Everything about Pentax: Welcome to Bojidar Dimitrov's Pentax K-Mount Page
General Understanding: The Understanding Series table of contents
Flash: Strobist: Lighting 101
Technique (simple): Welcome to Photozone!

Have fun!

05-20-2011, 05:07 PM   #5
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Under a hundred for a decent manual focus prime lens Pentax brand, you are looking for a lucky buy on a KA 50mm 1.7. The KA 2.0 50mm can often be bought for well under $100 but IMO is not the same quality (I own both in the M series).

There are some decent third party primes in the same class but I can't really offer any first hand experiences with them on a digital camera.

AF for under a $100 --- just plain forget it.

And to answer your question, any Pentax mount will work but only the A series and newer work on all cameras without using manual mode. The A lenses will auto adjust the aperture for you.
05-20-2011, 08:18 PM - 1 Like   #6
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To summarize some of the above:

* Any screwmount lens requires an adapter. They aren't tricky; but practice a bit to use them.
* Any Takumar lens is a screwmount, except those economy lenses called Takumar Bayonet.
* Any Pentax lens whose name starts with F or FA or DA is autofocus. All others, aren't.
* Any Pentax lens whose name starts with A, or is autofocus, has aperture automation.
* Any Pentax lens with a name starting with M, or without a letter, has a manual aperture.
* Aperture automation means the camera can control the aperture, and flash is easier to use.
* NO Pentax lenses have names starting with K. The lens MOUNTS are called K-something.

Now, a disagreement: Pentax (and compatible) autofocus lenses CAN sometimes be found used on eBay for well under US$100. The fine F35-70/3.5-4.5 can often be found on an old camera body for well under US$50. The fine FA100-300 (silver version) should be around US$100.

Good lenses are out there. Finding them isn't hard. Getting them CHEAP is another story. You need to do research, scan a zillion eBay listings, be patient and inexorable, and discipline yourself. Don't get caught up in bidding wars; you will lose. Set a price limit and don't bid over US$5 more. If you lose, don't worry; another auction will come along very soon. These are not rare items. There is always another lens.
05-20-2011, 08:19 PM   #7
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The cameras cost $500 or more, so it's not unreasonable to expect $100 lenses. Unfortunately, new lenses that are pretty good start at about half the cost of the camera, and go up from there.

To get back down to $100 and still pretty good, we trade off age, features and compatibility.
For Pentax, lenses have two classes. In the first group, the camera can adjust the aperture electronically. The lenses either have no aperture ring at all (like the kit lens) or the ring has an A setting next to the highest f number. Electronic control is great and your camera will love you. Since these lenses are probably manual focus, you'll have to enter a focal length yourself for SR to work well, and focus manually. People commonly call these KA mount lenses.

The second group is all the other lenses. For these, you use the aperture ring to set the aperture. Most of the time, that means only M mode, stop-down metering and hardly any cool features. But it's often worth the trouble to use a lens you couldn't afford otherwise. The details about using these lenses are here.

I can think of a few suggestions for $100 or less.

- Sigma Superwide II 24mm f2.8 - This lens has a few versions, from basic K mount, KA, and even an AF version, optically the same. The KA mount should be just under $100. It's not very flare resistant but it's sharp, handles well and a good value.

- SMC Pentax-A 28mm f2.8 - Another just under $100 lens. Pentax coatings do better with flare, and the focal length is close to a normal field of view.

- SMC Pentax-A 50mm f1.7 - Maybe $70-80. The reason these are affordable is because they used to be a kit lens on better cameras, not because you're giving up image quality.

- SMC Pentax-M 135mm f3.5 - About $50 or so. It's a very compact lens and has great image quality, unfortunately no A setting.

- SMC Pentax-M 200mm f4 - Large if you're used to the Pentax-M 135/3.5, but not too bad. It's maybe $75 or more, and an inexpensive way to try out a telephoto prime.
05-20-2011, 08:52 PM - 1 Like   #8
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QuoteOriginally posted by slr_neophyte Quote
....I've read a lot of good information on lenses, ....... - it seems even 2nd hand Pentax glass is expensive.
Well, that's exactly why I went for a Pentax as I kept hearing the word 'dirt cheap' all the while in most of the threads. Even M42s for that matter. But the reality is not that, even in the marketplace here i don't see that big difference from a new to an old. Having said that I still like the feeling that i am a Pentaxian and no regrets. Maybe we'll all get the lens we wanted someday.



QuoteOriginally posted by Ratmagiclady:
....(If that's you in that shot and you don't want it to be a 50ish in particular, check out the new 35/2.4. )
As rightly mentioned by Ratmagiclady, I own the 35/2.4 which I bought separately when I bought my camera without kit lens and am really happy with it just that the distance is too short for portraits. I was playing with it this morning and here is an example from that....this will be a treasure as well if you buy and keep looking like me for that 'someday'.

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05-21-2011, 09:59 PM   #9
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QuoteOriginally posted by sany Quote
Well, that's exactly why I went for a Pentax as I kept hearing the word 'dirt cheap' all the while in most of the threads. Even M42s for that matter. But the reality is not that, even in the marketplace here i don't see that big difference from a new to an old. Having said that I still like the feeling that i am a Pentaxian and no regrets. Maybe we'll all get the lens we wanted someday.


As rightly mentioned by Ratmagiclady, I own the 35/2.4 which I bought separately when I bought my camera without kit lens and am really happy with it just that the distance is too short for portraits. I was playing with it this morning and here is an example from that....this will be a treasure as well if you buy and keep looking like me for that 'someday'.
I've gotten away with a few "dirt cheap" by skulking around secondhand shops, pawn shops, and craigslist...
I paid, for instance, $$25 for my M 50 f1.7, which is really one of my favorite lenses. If you want deals, you're gonna have to be vigilant, know what you're looking for, and pound the seedier parts of the street. OTOH, if you're going to buy new lenses, Pentax seems to run a little higher than their counterparts. They also seem to run better quality... (Except the SDM).

Another note - I've found I like my aperture-ringed lenses for one very specific purpose - Video mode. There's no way to manually change exposure mid-shot if you're using an all electronic lens. I have an old tokina zoom that I've taken the detent pin out of, so the aperture ring shifts smoothly. That's my video lens.
05-21-2011, 11:53 PM   #10
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QuoteOriginally posted by sgtkashim Quote
I've gotten away with a few "dirt cheap" by skulking around secondhand shops, pawn shops, and craigslist...
I paid, for instance, $$25 for my M 50 f1.7, which is really one of my favorite lenses. If you want deals, you're gonna have to be vigilant, know what you're looking for, and pound the seedier parts of the street. OTOH, if you're going to buy new lenses, Pentax seems to run a little higher than their counterparts. They also seem to run better quality... (Except the SDM).
BEST lens bang for the buck. If you don't want to screw around with M mode on your camera but would like to have auto aperture, get the A version (currently pretty expensive though, usually $25-$40+ more on ebay).


05-22-2011, 06:33 AM   #11
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Presuming you already have the 18-55mm kit lens, choices that augment what you already have in your price range so far are:

A 50:1.7
F 35-70
FA 100-300

"A" type lenses are lots easier to use (auto everything except focus) than earlier lenses.

Keep checking keh.com for lenses with BGN grade (they are optically excellent in my experience.) http://www.keh.com/search?store=camera&brand=Pentax-Autofocus&category=Zoom-...price=0&r=SE&e

Last edited by newarts; 05-22-2011 at 06:39 AM.
05-24-2011, 10:35 AM   #12
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I got a 50mm f/2.0 Ricoh Rikenon XR for $25 locally after browsing through Kijiji (craigslist type website)

Full manual, REALLY sharp and fun to play with. Takes real nice pics of my son.
05-25-2011, 03:04 AM   #13
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Original Poster
Thanks for the heaps of info. Now, to add to my confusion...is there somewhere a newbie like me can go for an understanding of the terminology which seems so widely used that I should just "know" what it means, but really have no idea what's being talked about? Examples of words I'm running across while I'm trying to learn about lenses and mounts and adapters: flange, clips, infinity focus? Is there an "everything you ever need to know about lenses" thread somewhere? Or an article?
05-25-2011, 05:44 AM   #14
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Here is a glossary, it might help some.
The Photographic Glossary: your Photo help page, from Aberration to Byte
05-25-2011, 06:13 AM   #15
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QuoteOriginally posted by slr_neophyte Quote
Thanks for the heaps of info. Now, to add to my confusion...is there somewhere a newbie like me can go for an understanding of the terminology which seems so widely used that I should just "know" what it means, but really have no idea what's being talked about? Examples of words I'm running across while I'm trying to learn about lenses and mounts and adapters: flange, clips, infinity focus? Is there an "everything you ever need to know about lenses" thread somewhere? Or an article?
SLR Lens Mount Identification Guide

Lens mount - Wikipedia, the free encyclopedia

Pentax K mount - Wikipedia, the free encyclopedia

Welcome to Bojidar Dimitrov's Pentax K-Mount Page

Pentax Reviews - Pentax Lens Reviews & Pentax Lens Database

Third-Party Lenses for Pentax - Pentax Third-Party Lens Review Database

Pentax in the WWW
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