[Aegon]

If you own a K mount digital camera, you probably should own this lens.

Even if your camera doesn't support SDM. The lens has a screw drive too.

[audiobomber]

If you own a K mount digital camera, you probably should own this lens.

Even if your camera doesn't support SDM. The lens has a screw drive too.

Why is that? It's no sharper than a 50mm 1.4 according to Photozone. What is it about the 50-135mm that's so wonderful? I can crop a 50mm 1.4 shot on my K20D and it will be sharper than a K100DS at all focal lengths below 135mm, and equal at 135mm.

[Aegon]

Well, I suppose that approach has merit. Buy an FA 31mm LTD and crop to zoom. You won't need another lens.

When the K30D comes out you'll get even more zoom!

In 20 years, you won't need any lens except for a good 10mm and a cropping zoom.

I guess we just have different approaches. You are one of the exceptions to my statement that you probably should own this lens.

[audiobomber]

Well, I suppose that approach has merit. Buy an FA 31mm LTD and crop to zoom. You won't need another lens.

When the K30D comes out you'll get even more zoom!

In 20 years, you won't need any lens except for a good 10mm and a cropping zoom.

I guess we just have different approaches. You are one of the exceptions to my statement that you probably should own this lens.

I wasn't talking about me. The OP is complaining of softness with a K100DS and 50mm 1.4. The question is should he buy a 50-135mm for his K100DS? I say no, because if it's sharpness he's after a K20 with a 50mm will be sharper than a K100DS with ANY other lens. A 50-135 is neck in neck with the 50mm in terms of sharpness, so how would getting one help? All it offers over the 50mm is longer FL.

[audiobomber]

the K100D Super?

okay so after reading so much about how great this DA* lens is... I 'm tempted to get it, especially after I read that portraits are great at 75-100 mm.

That 75mm means the thirty-five millimeter equivalent. On a K100DS, your 50mm lens is a 75mm equivalent, and is a great portrait lens. You just have to learn to handle it in low light.

Another possibilty would be to get a good bounce flash and diffuser. Maybe even learn to use your new flash off camera. You don't actually need to upgrade your camera or lens. They are fully up to the task of taking amazing baby photos.

[Marc Sabatella]

What is it about the 50-135mm that's so wonderful? I can crop a 50mm 1.4 shot on my K20D and it will be sharper than a K100DS at all focal lengths below 135mm, and equal at 135mm.

I can't prove you are wrong, but that seems a bold enough claim that the burden of proof here would be yours. Frankly, I'm very doubtful that the actual resolution of a cropped image from a K20D + 50/1.4 would exceed that of one from the K100D + 50-135 @ 135. But I'm willing to be proven wrong with photographic evidence, and indeed, am quite curious!

But of course, that's still apples to oranges. If you are right, then if one has a K100D & 50/1.4, one can get better results by upgrading the camera than by upgrading the lens. But, what if one wants a longer telephoto lens for the K20D? One way or another, if you want better telephoto performance, you need a telephoto lens. Not that is necessarily exactly what the OP needs - I'm not at all convinced it is. I suspect it's primarily a technique issue.

[Marc Sabatella]

That 75mm means the thirty-five millimeter equivalent.

Although of course, the question of the best portrait range is also subjective. Sure, 75-100 is considered nice in 35mm terms, but so is the range from 100-135 - which is to say, up to 90 in APS-C terms. Really, 50mm for APS-C (75 for 35mm) is kind of bare minimum in terms of focal length in the eyes of many. I know I find it too short most of the time (not that I'm a pro portrait shooter or anything): I'm either framing too much of the scene, or coming in too close. Sure, I could use a 50 and crop, and that's pretty much exactly what I've been doing. But I'm finding the M100/2.8 I just picked up really promising. Sure, at 150mm in 35mm equivalent, it's on the long side of what even those who like the 100-135 range might recommend. But it actually suits me fine.

[virgilr]

As many have suggested, a little post processing can help a long ways in terms of managing noise!

I find that with my K100D super, in decent low lighting (when I say decent, I mean a normal tungsten/halogen/fluorescent source near the subject), the noise is quite controlled at ISO 800, and a touch of noise reduction (around 30) for both standard (grey scale) and color in Adobe Lightroom works wonders! Even at that, when printed at 8x10, the noise isn't that horrible, a nice film-like quality.

I find that my camera at least ( I don't want to speak for all K100D supers) does not impose a high level of color noise, mostly grey scale noise, and I'm even willing to compromise using ISO 1600 at times, clean it out a bit in Lightroom, and enjoy a fairly decent image!

[cwood]

Why is that? It's no sharper than a 50mm 1.4 according to Photozone. What is it about the 50-135mm that's so wonderful? I can crop a 50mm 1.4 shot on my K20D and it will be sharper than a K100DS at all focal lengths below 135mm, and equal at 135mm.

You really think so eh?

[audiobomber]

You really think so eh?

I do think so, here's my reasoning:

- The 50mm 1.4 and 50-135 have similar MTF scores
- The K20D has a lower noise CMOS sensor that the K100DS CCD sensor, so better IQ
- The K20D has 14.6mp, so can be cropped to an equivalent fov of 135mm and still have about 6mp. At any larger FOV it will have more pixels, therefore higher resolution

I know from personal experience that there's no lens one can mount on a K100 that will make it equal the resolution of a K20. So IMO mounting a 50-135 on a K100 is overkill.

[Knight]

I use Pentax K100D for a year and as you know my camera doesn't support SDM. Is that mean I can't use autofocus function with DA* series?

[cpopham]

The K20D has a lower noise CMOS sensor that the K100DS CCD sensor, so better IQ

Presumably, you're talking about higher ISO, 800 - 3200? I think perhaps you might rethink this if you compared high ISO photos from both camera taken with identical exposures. If you take a look at, for example, Imaging Resource's Comparometer - compare the high ISO photos at 100%. If you really want, resize the K20 image down to 6mpixel. The noise is definitely different, perhaps more pleasing even, but I'm not sure it can really be described as lower noise.

On the other hand, if you're talking about low ISO the noise is barely going to factor into it at all.

The K20D has 14.6mp, so can be cropped to an equivalent fov of 135mm and still have about 6mp. At any larger FOV it will have more pixels, therefore higher resolution

Isn't a crop for magnification a linear reduction in both dimensions? 50 to 135mm is 2.7x . 14.6 divided by 2.7^2 is about 2 mpixel.

I know from personal experience that there's no lens one can mount on a K100 that will make it equal the resolution of a K20. So IMO mounting a 50-135 on a K100 is overkill.

I disagree absolutely. Consider this - I can buy (here in New Zealand) a 50-135 for about 5/6ths the price of a K20 - if I bought a K20 and then used my 50-200 on it would that be better than my K100 with a 50-135?

And then there are the possibilities the faster aperture opens up...

[cpopham]

I use Pentax K100D for a year and as you know my camera doesn't support SDM. Is that mean I can't use autofocus function with DA* series?

No it doesn't. the current DA* lenses (16-50, 50-135, 200 and 300) are described as having a KAF2 mount. That means they have both the SDM power coupler, and conventional screw drive AF. They will autofocus on your K100, but using the body's built in motor, rather than the SDM in the lens.

The recently released 17-70 f4 is described as having a KAF3 mount. This means it does not have the conventional screw drive, only the SDM power coupling. This lens will not autofocus on your K100.

Whether or not future DA* lenses will be KAF2 or KAF3 is the subject of considerable speculation, but Pentax have stated they will not be forever.

While we will continue to develop lenses for each type of autofocus system, we will also phase out lenses that support both types of focusing simultaneously. Due to issues of cost, development timeframe and other factors, in the future, PENTAX lenses will either support SDM focusing or body-based focusing, but not both.

Pentax posted a FAQ when the 17-70 was released:
DA 17-70 FAQ (link to PDF)

[Lance B]

[QUOTE=laissezfaire;344436]the K100D Super?

okay so after reading so much about how great this DA* lens is... I 'm tempted to get it, especially after I read that portraits are great at 75-100 mm.

I have a few questions:

1) is this too good a lens for my K100D Super? (I got this to take pics of my newborn but now that I discovered a love of taking pictures, I regret not getting the K10)

Definitely NOT! The K100D Super has a fantastic 6Mp sensor and will suit the DA*50-135 perfectly. Do NOT think that the 6Mp sensor is not up to the task, as it is one of the best sensors out there, as implemented by Pentax. Some of my BEST photos have been taken with the *ist D which uses this very same sensor.

2) Is some of the softness I'm getting bad shooting, indoor lighting (despite my 50mm 1.4 lens) or 6MP? In other words, maybe the lens won't help.

It is definitely not the sensor. Maybe camera shake or poor focus, but definitely *not* the 6Mp sensor. The other reason maybe that you are shooting at wide open f1.4 aperture. At f1.4, the lens can be a little soft and added to that there is *very little* Depth of Field(DOF). Depth Of Field(DOF) relates to the amount of your subject that is in focus, ie from front to rear of the subject. If you shoot at f1.4, and say 6 feet distance, the DOF is only 2.88inches! This is the amount of your subject that is in focus, 2.88inches! If you choose f8 and 6 feet distance, then your DOF becomes 1.38 feet, which is a huge difference. So you can see that with the larger *numbered* apertures, but smaller physical actual aperture size, like f8, f11 etc, you get more DOF.

The other advantage of "stopping a lens down", ie going to a larger numbered aperture, you usually get better sharpness from a lens. The FA50 f1.4 gets better sharpness from about f2 to f2.8 onwards and is probably at it's best at about f8.

See Photozones resolution results here:
Pentax SMC-FA 50mm f/1.4 - Review / Lab Test Report

The disadvantage of going to a larger numbered aperture is that your shutter speeds slow, so in dim light you may need to up the ISO and make sure your SR is turned on.

For a DOF explanation and on line calculations, go here:
Online Depth of Field Calculator

3) What lens filter do folks recommend for all around use,e.g. primarily to protect the lens itself.

I do not use any filters other than a polariser for bright sunshine shooting or my ND graduateds. If you feel you are likely to damage your front element, then get the best filter you can afford, like a B&W UV or a Hoya Pro model. Lens hoods tend to give you protection as they keep objects away from the front element.

I hope I have been clear with my explanations.

[dave sz]

the way i feel about my k100, i can't see myself pending more on a lens than i did on a ow older body. if i can spend that much on a lens, i'd rather upgrade the body...