Pentax K-x and M42 lens

pentax k-x white
I have been trying out different M42 lens on my Pentax K-x. Results in the final images are good but I find that K-x does have some minor glitches with M42 lens when compared to Pentax K20D.
  • I can't use Av mode on M42 lens like K20D. I found myself under-expose by a big factor as in 2 to 3 stops. I have not found if the difference is consistent so that a simple +Ev compensation will make K-x work with M42 lens in Av mode.
  • For consistent metering, I have to use M mode together with either green button or (+/-) button for metering. I prefer the use of (+/-) button as K-x's green button location is awkward to access in the field. The (+/-) button is more natural for me to use.
  • Ev compensation is omitted in K-x. This is unlike K20D which allow Ev compensation even in manual mode. I get spoiled with Ev compensation so that I can set a preset compensation adjustment for consistency with an M42 lens.
  • I do miss the red focal point overlay for focus reference
  • It is difficult to see bottom of viewfinder especially in bright daylight setting. The green hexagon is not bright enough to view in K-x. I rely mostly on the beep which is unsettling in the shooting.

Results are quite good when I tried my Pentax K-x with Vivitar 70-150mm f/3.8 from Kiron in M42 mount. In some of the close up, I used the Cosina 1:1 matched macro adapter which works like diopter with +3 to +4 magnification.

pentax k-x and vivitar 70-150mm f/3.8 in m42

pentax k-x and vivitar 70-150mm f/3.8 in m42

pentax k-x and vivitar 70-150mm f/3.8 in m42

pentax k-x and vivitar 70-150mm f/3.8 in m42

pentax k-x and vivitar 70-150mm f/3.8 in m42
Impressions & Notes
  • The Kiron zoom lens is great in terms of sharpness. It is not too big and works well in K-x.
  • The close up works in the 70mm end and I think it is about 1:4 in magnification. With the diopter, it is roughly around 1:3
  • The catch-in focus is absent like many M42 lens.
  • Metering is center weighted and I have not tried the trick with aluminum foil to see if matrix metering and catch-in focus can be resumed in this m42 zoom on K-x
  • As mentioned, I used M mode and green or (+/-) button for metering.



Anonymous said...

The droplets on those photos are really sharp! Those images I think work well large, really large. Nice set Hin!

ps- and thank you for updating your blog roll, we're glad you're enjoying our posts!

Sarah said...

Great reviews! I have a KX also and love it. Your reviews helped to pick it out wanted to say thanks. After having it for a few weeks I am now looking at the Tamron 70-300 macro. I noticed you reviewed this lens on another camera have you used it on your kx? If so what are your thoughts?

Hin Man said...

@Somanna, thank you.

@Sarah, the Tamron 70-300mm f/4.0-5.6 works pretty much the same way like my reported experience with K20D. It still has the same issues with PF/CA with purple fringing around high contrast area. You can see the how K-x and the Tamron zoom work in SeaWorld Part 1 and SeaWorld Part 2

The Pentax DA 55-300mm f/4.0-5.8 will be a better lens.

LaRee Brownell said...

Hey Sarah, I went out with my new k-x and the tamron 70-300. I was happy with the results. The focus speed on the k-x makes taking photos of birds in flight much easier than I am used to. I didn't notice as much PF/CA with the k-x. The k10d was the worse for pf, the k20d less and I feel the k-x is even less prone. That is only my feeling from one outing, so in other circumstances I may find different.

Anonymous said...

Hello Hin Man and thanks for your work
Tried today my M42's lenses on Kx and the green button doesn't work as contrary as with the "K" or M lenses. I use a real Pentax ring. Everything is ok with the *ist Ds. Do u have an idea of what's going on ?

Hin Man said...

@Philip, first thing to check is ensure that you have not assigned Green button for another purpose such as optical preview or other function. In M mode, the (+/-) Av button serve the same purpose as the Green button. Give that a try also. Unlike K or M manual lenses, you will not hear any close of aperture blades as the lens is already stopped down to the set aperture. You note the changes in the shutter if the lighting scene change. It is easy to get confused when the shutter does not change when shooting scene are similar resulting in identical shutter speed.

Anonymous said...

Thanks for your quick and nice answer. You were right. The lack of noise made me worry, but it works. Not so good as with the *ist Ds in my opinion.
Sincerely yours.

lyans said...

Hi Hin man,
It was very useful information you wrote.

I just bought white pentax-kx 4 months ago. On that class there are Canon 500D, Nikon
D5000, Olympus E-620, Sony a380. I choose with many aspect as see in price/performance/quality/design/feature has a good value. On couples days before, i tried searching old Lens 50mm f/1.4, as many peoples said that this is a very good lens.
Do you have any experience using this type of lens ?
I think is on M42 mount.


Hin Man said...

Hi Lyans,

I personally prefer Pentax A 50mm f/1.7 in K-mount. And with the A setting, you don't miss much except the AF. The A 50mm f/1.7 is a sharp lens when I tried it before. If you love smaller size and don't mind the costly price, the DA 40mm f/2.8 will be a great normal lens to pursue. With the high ISO capability in K-x, I find the f/2.8 to be fast enough for most uses.

With M42 lens, you have to rely on an m42 to K mount adapter, make sure you look for the genuine m42 adapter.

Unknown said...

I bought a kiron 70-210mm f/4.5 lens and I can't mount it to my pentax K-x. Do I need an adapter or something? I am so lost, help! :(

Post a Comment



Welcome to Hin's Photo Corner, this is my learning blog on photography, blogging and advertising. And I hope you enjoy your visit. For contact, please comment in blog post or email me directly hintheman at


B&H Best Deals