Tokina 17mm or Pentax kit lens?

[katherine_jones2]

I'm currently thinking of buying a pentax digital SLR. I currently

own a super A, 50mm f1.7 A, 28mm M and 100mm macro M. I really like

this set-up, and may keep the super A and film for some purposes.

 

I'm pretty happy with manual focus, and I don't think the metering

limitations with M lenses will bother me too much . I tend to take

landscapes/travel/macro. Small and light is important. I don't like

large lenses. I'd rather carry one small prime and think in that

focal length and have a nice compact package (some of my best shots

were when I only had a 28 and went travelling for a month in Norway).

 

I've seen a second hand manual focus tokina 17mm. I think it is PK

fit not PKA. Is this a good lens, or is it complete pants? Would I

get better quality from the 18-45mm kit lens, bearing in mind I would

use it mainly at the wide end? I like the thought of putting the 17mm

on my film camera for the odd fun shot, but if it is optically

rubbish it probably isn't worth bothering(I tend to make larger

prints out of my 28mm film shots as they are good for putting on the

wall at home). I'm a student, but I like good value for money, hence

the old pentax gear has served me well, but despite my initial

reluctance I've finally succumbed to temptation (and prices have

dropped a lot!)

[glenn_holden]

Katherine:

 

Most likely, you will not be happy with the tokina 17 mm lens if it is not designed for a digital (1.5 crop factor) camera. It's to do with the design of the sensor in the digital camera, it requires the light rays to enter directly onto the surface rather than from an angle. If the light strikes the surface from an angle, the light ray "smears" over several sensor cells instead of just one. A digital lens is designed for this, but a film lens isn't. Film is more tolerant of the angle of approach to the surface.

 

By the way, it only applies to wide angle lens, after about 50 mm there isn't much difference between a digital lens and a film lens except for the coatings.

 

If you do a search on this web site, there are some illustrations showing why this effect occurs.

 

Hope this helps.

 

LGH

[stephen hazelton]

I've got a Tokina 17mm lens. I like it and have used it a fair bit.

 

Back when I got it, Tokina was advertising a new AT-X line of lenses that included the new 17mm. The new AT-X lens was about double the price that I paid for the non-AT-X version. I think the AT-X was upgrading to autofocus, but it may also have included new lens formulations. Anyway, there's more than one version of "Tokina 17mm" out there, so don't just assume that all are the same.

 

A while back, I read a post on the subject and one poster said he had tried one and "it was not critically sharp". That's probably true. I'm shooting full-frame with mine, generally at f/11 or so, generally making 4x6 prints, and the sharpness is okay for me. But if you plan to use it with a crop-factor digital, and make any enlargements, you want to make sure you can try it before you're stuck with it. The AT-X version may be lots better, I haven't tried it.

 

Something more subtle is that a 17mm lens with f/3.5 can be hard to focus manually in a lot of cases. IE, it has considerable depth of field wide open, and lots of times, it just works better to use the focusing scale. That's not an issue with this particular lens, but any of similar focal length and aperture.

 

It IS fun to use with film by the way; great for flower and IR applications, anywhere where wider is better. At the time I got it, it was the most "bang for the buck" for wide angle, and still holds up well in that regard.

[katherine_jones2]

I think this is a non-ATX one i.e. quite old, certainly not autofocus.

[zane1664879013]

Mr. Holden, you're quite mistaken about the reasons for the digital crop factor. It has nothing to do with so-called "angle of approach". Crop factor results from the sensor being smaller than the standard 24x36 film frame. For Pentax, the crop factor is 1.5X, turning a standard 50mm lens into a 75mm one. An old 17mm would effectively become 25.5 on the dSLR.

 

"Full frame" dSLRs do not have a crop factor, and you pay dearly for the additional size. Pentax does not offer a full frame dSLR.

[zane1664879013]

Also, the digital crop factor applies to all lenses, not just wide angles.

[katherine_jones2]

I don't think he is talking about crop factor, I think he is talking about wide

angles designed for 35mm film being less able than those designed for

digital-Olympus really talk up their lenses being designed for a digital sensor

and better for wide angle despite a higher crop factor. I think I saw a diagram

once that explained it, and it seemed to make sense, however lots of people

are using non-digital short lenses on their new digital SLRs with smaller

sensors, and it isn't always disasterous.

 

Ideally someone with a knackered old tokina has tried putting it on an APS-C

sensor and can tell me the results. However, I suspect that most people have

more modern lenses and upgrade lenses as well when they go to digital.

 

If I was rich, and I ever saw one I'd grap a PKA 20mm f2.8 or a PK 17mm. I

have not found either for sale and I expect they will go for silly prices (in which

case might as well save up for something new).

 

What I love is the robustness and compactness of the old primes, and I really

like the simplicity of a single focal length.

 

I'm aware my current lenses will change effective focal length. I'm happy

about this with my 100mm macro. I'm just thinking wide angle might have to

stay with film for a time. I don't want extremes but I do love a nice 28

equivalent prime.

 

Pentax is never going to produce a nice 17mm affordable digital prime as it

won't sell to the majority of users. Shame for me, but hey, I'd like to see them

shift some cameras as I've become Pentaxed (with a penchant for Olympus, of

course) and have liked their tradition of small and light..

[glenn_holden]

OK folks, let's try this one again.

 

I guess I shouldn't have mentioned the crop factor, everyone is getting confused. The difference between an optical length (not effective length) 17 mm lens for film and for digital (other than the coverage area, which is of course, smaller for the digital lens than the film lens) is in the placement of the rear lens element. As I understand it, with a conventional wide angle 17 mm lens the light beam "spreads out" more and a light ray will hit more than one cell on the sensor. This gives a blury picture, especially around the edges. On a lens designed for digital, due to the optical design and placement of the rear element, the light rays enter more at 90 degrees to the sensor, so you don't have the blurry effect. In fact, some sensors have little "curtains" around each cell to minimize this effect.

 

With the longer optical length lens, the light beam on both the digital and the film lens approach the sensor plane at almost a 90 degree angle anyway, so it isn't as much a concern as it is with short focal length lens.

 

The bottom line is that a 17 mm optical length lens designed for digital should give you better results than a 17 mm lens designed for film regardless of the "quality" of the film lens.

 

LGH

 

ps: Check carefully, some very wide angle lens will not fit the Pentax DS, the rear element is too far in, and I speak from experience on this one.

[alan_chan4]

Tokina AT-X 17mm has never been made in PK mount unfortunately. Only the old manual focus version (67mm filter) was available, and they have different optics. If you are going to use it wide open, better opt for the kit lens which is not bad imho. But for the best optical performance, you might start saving and buy the DA14/2.8.

[zane1664879013]

No confusion here, Mr. Holden.

 

Lenses "designed for film" will probably work on the Pentax dSLR. A person just needs to do some research to understand issues regarding 1) crop factor, 2) whether through-the-lens metering works properly, and 3) whether the camera will provide proper aperture control.

 

A lens described as "designed for digital" doesn't give you enough info. It doesn't necessarily mean it works only on dSLRs. Some lenses marketed as "digital" *do* provide full-frame coverage when used on a film body, others do not. Also, "digital" lenses don't have different coating requirements than other lenses. Light is light and a coating for film works just fine for digital.

 

This concept of "hitting more than one cell" is not the fundamental mechanism behind crop factor. It is simply the difference in area between a sensor chip vs. a 24x36mm film frame. Again, longer focal length lenses are affected in exactly the same way and in the same amount as shorter, wider lenses. Do the math, multiply by 1.5.

[alan_gage]

"No confusion here, Mr. Holden."

 

There does still seem to be some. I'm not going to say if he's correct or not because I don't know. But he's not referring to crop factor at all.

 

Alan

[zane1664879013]

Okay, after re-reading everything with fresh eyes, I see what Mr. Holden is saying. Apologies for harping about crop factor.

 

But I think this "light leaves a 'digital' lens at a 90 degree angle" story is pure MarketSpeak. THEY want you to buy all new lenses for your dSLR, and a little technobabble goes a long way toward spurring sales.

 

Consider this writeup:

 

http://www.kenrockwell.com/tech/wideslr.htm

 

I say buy rugged old primes, use them, and be happy. And multiply by 1.5. Cheers-

[katherine_jones2]

So if the pre-ATX PK mount Tokina has a different design is it any good?

[glenn_holden]

Zane:

 

Intersting article, thanks for the reference, I admit that I must agree with most of it.

 

Not to draw out this thread, but lens designed for digital cameras do have different requirements for coatings than film cameras. When the light bean exits the rear element on a film lens, and strikes the film, something like 99.99% of the light is absorbed by the film and the anti-halation backing of the film so there is no light reflected back from the film onto the rear lens element.

 

When using the digital sensor, instead of film, the light beam strikes the tiny lens in front of each sensor cell and some of the light is reflected back onto the rear element then back again to the sensor and lowers the effective image contrast. To correct for this, the manufacturer's put additional anti-reflective coating on the surface of the rear lens element.

 

I also used to think this was marketing hype, there is a good article in Pop Photography March, 2004 when they actually tested the various digital lens and film lens and found that indeed, with one exception, there was a difference, the digital lens did give a higher contrast image. Sorry, I don't remember the author or know if the article is on line or not.

 

Katharine:

 

How "good" a lens is somewhat subjective. Sure, you can get acceptable images with a film lens on the Pentax ist D, especially if you do some post processing in Photo Shop and bring the contrast up, etc. But I think your origional question was about the 18-45 kit lens, in my opinion, it is well worth the price and you won't be disappointed. I'm sure you'll acquire other lens as time goes on.

 

LGH

[bill_oneill]

Hi Katherine,

 

I have that lens. The older non-ATX Tokina 17mm. I have tried it on my *istD and on film bodies. I don't think much of it on the digital. It's a bit better on film, but still not good enough for anything bigger than a 5x7.

 

If you like, I will shoot an image with it and send it to you. You can be the judge. Let me know and supply me with an e-mail address that will take a 3MB file (I won't try to send raw).

 

Just let me know.

 

Bill

[wayne_young1]

I have both the Tokina 17mm and the Pentax 18-55 "kit" lens, so I thought I'd post the results of a little experiment I did. I took two images - one with each lens. Hopefully, the two files will be attached to this post. If not ... they will appear in subsequent posts :-)<div></div>

[wayne_young1]

OK - I can only load one at a time, so here is the image for the Tokina:<div></div>

[wayne_young1]

<h4>Test setup:</h4>

 

<ul>

<li>Tripod mounted *istDS.</tr>

<li>ASA : 200

<li>Color Balance : tungsten

<li>F ratio : f8

<li>Shutter speed : 1 second

</ul>

 

<p>Images presented 1:1, highest JPEG quality - there is no difference between what you see and what was in the original. No, really!!</p>

 

<p>As you can see, both lenses perform pretty much identically in the centre. I certainly couldn't tell the difference. However, at the corner of the image, there is a noticeable difference between the two. The Pentax is slightly sharper, but suffers quite a bit of chromatic aberation (red/cyan color fringing on the picture frame). The Tokina - on the other hand - is not quite so sharp, but hardly has any color fringing at all.</p>

 

<p>As for the rear-element spacing thing .... sorry, but I think it's marketing hog-wash to get us to pony-up for expensive new lenses. The rear-element to image-plane distance was *further* on the Tokina than it was on the Pentax. So by that measure, my 20-year-old Tokina is a better "digital" lens than my brand-spanking-new Pentax.</p>

 

<p>So these are the cold observations. What do I think about these lenses ? I like both. For most practical purposes, there is no difference. I like the Pentax because it's light and can zoom out to 55mm, which makes a good portrait lens. But I have a special place in my heart for the Tokina. On my beat-up old K1000, you could get a full 100 degrees field of view from corner to corner. Not only that - but it's highly corrected, so straight lines near the edge of the frame stay straight. You don't need a shift-lens to take pictures of tall buildings - just point at the base and throw the bottom half of the picture away :) Alas, since the sensor size in my DS is only 24x16mm, the images it produces are a pale shadow of it's former self. I'm going to have to get an 11mm lens (or a full-format DSLR) to experience that again.</p>

[wayne_young1]

<p>Arrrgggghh !! So sorry! I think a spurious bit of HTML ( a "/tr") has krept in and it seems to have messed up the page. I can't see how to edit my post, so I'm posting a replacement. If you are the moderator, please delete my previous post and keep this one. Thanks.</p>

 

<h4>Test setup:</h4>

 

<ul>

<li>Tripod mounted *istDS.

<li>ASA : 200

<li>Color Balance : tungsten

<li>F ratio : f8

<li>Shutter speed : 1 second

</ul>

 

<p>Images presented 1:1, highest JPEG quality - there is no difference between what you see and what was in the original. No, really!!</p>

 

<p>As you can see, both lenses perform pretty much identically in the centre. I certainly couldn't tell the difference. However, at the corner of the image, there is a noticeable difference between the two. The Pentax is slightly sharper, but suffers quite a bit of chromatic aberation (red/cyan color fringing on the picture frame). The Tokina - on the other hand - is not quite so sharp, but hardly has any color fringing at all.</p>

 

<p>As for the rear-element spacing thing .... sorry, but I think it's marketing hog-wash to get us to pony-up for expensive new lenses. The rear-element to image-plane distance was *further* on the Tokina than it was on the Pentax. So by that measure, my 20-year-old Tokina is a better "digital" lens than my brand-spanking-new Pentax.</p>

 

<p>So these are the cold observations. What do I think about these lenses ? I like both. For most practical purposes, there is no difference. I like the Pentax because it's light and can zoom out to 55mm, which makes a good portrait lens. But I have a special place in my heart for the Tokina. On my beat-up old K1000, you could get a full 100 degrees field of view from corner to corner. Not only that - but it's highly corrected, so straight lines near the edge of the frame stay straight. You don't need a shift-lens to take pictures of tall buildings - just point at the base and throw the bottom half of the picture away :) Alas, since the sensor size in my DS is only 24x16mm, the images it produces are a pale shadow of it's former self. I'm going to have to get an 11mm lens (or a full-format DSLR) to experience that again.</p>

[katherine_jones2]

Thanks Wayne. That is extremely helpful-just the kind of advice I needed!

 

I think I would be happy with either lens, so I'll see which is cheaper. The Tokina does have the advantage I can stick in on my Super A. BTW Do you know the weight difference between the lenses. I assume the Tokina is pretty rugged but a bit heavier?

[brett_st_pierre]

Kate, the Tokina weighs about 400g compared to the 'kit' DA18-55 at 225g.

 

I don't have the Tokina but I do have the Tamron SP17mm f3.5 which is of the same era and tested a bit better than the Tokina on film back then. I was happy with it on my Pentax film SLRs. On digital I don't like the Tamron so much, it seemed sharp on film but not so much on digital - also the colour rendition is very cool (but of course fixable in editing) - you are talking about the Tokina however and it might have made the transition to digital better than the Tamron.

 

The DA18-55 is a good kit lens rather than a great one. The best wide angle zoom to have is the DA16-45/4 ED AL which is a great lens but pricey so may not suit your "student" price range.

 

Personally I would go for the DA18-55 in your circumstances, it will give you the most functionality with the Pentax DSLRs and from what i have seen on other threads the Tokina isn't stellar (but would suit your film body as you say) - but then again you might be a 'prime' girl and I can't argue with that.

 

Have you tried looking at sample photos taken with the 17mm AT-X on pbase? Go to the URL: http://www.pbase.com/cameras/tokina/atx_17_af_pro

 

Regards

[wayne_young1]

Well - my Tokina 17mm weighs 300g, and I measure the 18-55 kit lens at around 230g, so there isn't a whole lot in it (about 2oz. for the metrically challenged :-)

[mawz]

You're essentially comparing a medium/high-end prime to a kit lens. This speaks rather well for the kit. That 17mm goes used for twice what an 18-55 is new in my experience (I was drooling over the Tokina 17mm in Nikon AI a while back, before I jumped to Pentax).

 

If you need better optical performance, I'd look at the 16-45 f4, it's a fair bit more money than the 18-55, but even more lens. I'd expect the 16-45 to outperform the 17mm at the edges, not to mention it is wider (24mm equiv at 16mm)