Simon, it's a pity I didn't see your post earlier.

I have this lens, I bought it 20 years ago, when I was shooting film with a Praktica. I got it second hand from LCE. I was not particularly impressed with it then. When I got a M42-K adapter for my K100D, I tried out the Hoya, and was still disappointed (so the 1.5 crop factor didn't help).

As you know the lens is "automatic", that is, it has the pin to shut down the diaphragm, but no manual override. I decided that I would adapt the lens so that the auto pin is permanently pushed in. Since it is a cheap lens (it was cheap when I first bought it), I didn't care if I trashed it.

I managed to remove the back and do the adaption without losing any parts. I also dismantled it from the front element to the diaphragm, clean it and put it back again in the right order (I learned that with wide angle lenses the edges of the elements are painted black, so be careful not to scratch this paint - you can do minor touch ups with a Sharpie). I even scraped off the back paint so that focus trap and exposure metering worked. These are all things that I have done, or want to do to other lenses.

So I learned a lot from this lens, and it does not matter much that it really isn't too good because what I have learned from it was worth the small amount I had paid for it. And I still have a use for it: currently it is the "body cap" for my old Praktica PLC2!

Richard

Lilly, your kit lens has Quick Shift (assuming it is not the L version). You let the body auto focus, and then you can change the focus by turning the focus ring yourself without having to switch to MF.

Richard

LOL, I guess that reflects badly on me, since I am usually in on a Friday and Saturday night!

Hmm, I wonder if any Top Gear viewers have heard of DVRs

But thanks for the tip. Firstly to know when to get the most number of people possible for an auction where I am selling, and secondly for the times when it is best to bid because there will be less people looking!

Richard

OK, so when is the best time to end an ebay auction? (I have two M lenses - 135/3.5 and 35/2.8 to sell, so we're not talking large value here.)

Richard

I have several M lenses (M50/1.4, M50/4 Macro, M135/3.5 M35/2.8, the last two are surplus to requirements...) and I have a K100D (not Super). The following, I believe, is common to all the digital Pentax cameras, but it will certainly apply to your camera.

When I attach an M lens the aperture coupler in the camera is in a fixed position so that when the lens is rotated in the K mount the aperture lever on the M lens is moved against a spring in the lens. This opens the lens to full aperture. You can do this yourself to the lens when it is off the camera - set the lens to an intermediate f-number, say f/8, and watch that as you move the lever on the lens the aperture will vary between f/8 and fully open. The aperture ring provides an end-stop and the spring in the lens will pull the aperture closed down to this end-stop.

So, in all modes on the K100D the lens will be fully open: if you use Av or M the lens will be fully open. In M, as others have mentioned, if you have set the camera to allow you to use the aperture ring, when you press the AE-L button the camera aperture coupler will move as far as it can (you can hear this) and this movement allows the spring in the lens to pull the aperture to the end-stop set by the aperture ring: the lens stops down (the viewfinder goes dim for smaller apertures). When the lens has stopped down, the camera will meter.

Similarly, in M mode (and only in M mode) when you take a shot, the camera aperture coupler will move which allows the spring in the lens to stop down the lens to the value set by the aperture ring. Then the shutter will be released.

You say:

So this seems to indicate that the camera aperture coupler is moving. If you use an A lens, then the aperture will be wide open when you attach the lens, and if you use the A setting on the lens, then the aperture coupler in the body will move only sufficiently for the lens to be stopped down to the f-number set in the body when you take a shot. (For M lenses the camera does not know how far to move the coupler, so it always moves it as far as it can.) Do A lenses expose properly? If you set a small aperture in the body when using an A lens set to 'A' and take a shot, is it exposed correctly in Av mode? If A lenses expose correctly then I would say that the camera coupler works.

If you use optical DOF preview on all lenses (including A and M), you can see the lens stop down in the viewfinder. Try M mode with your M lens and use DOF preview. Hold the lever so that it is constantly on DOF preview and turn the aperture ring. Does the light in the viewfinder change? If not, then there is a problem between the coupling between the camera and lens. And if A lenses expose correctly, then the problem is with the aperture lever on the lens.

By the way, you say that:

In Av mode, if you press AE-L the camera should lock auto exposure, so you'll hear a beep and see a star next to the f-number (F-- if you are using an M lens).

I hope this helps.

Richard

I could not help noticing this in the description

I wonder if he would consider doing a swap with my old inky Parker pen that I used at school 30 years ago?

Richard

It is worth taking this a bit further. M = male 42 = 42mm diameter 1mm pitch thread. Theer is also T-mount that is M42 but 0.75mm pitch, but usually if the lens is T-mount is is described as such.

Also note that there is no connection between the diaphragm on an M42 lens and a digital body so you have to use stop down metering. This is no great issue because it means that you can use Av (and, of course M). For K and M lenses there is one-way connection between the digital body and the lens. Before the shutter opens the camera stops down the lens to the setting on the aperture ring. The camera does not know the setting, in M mode it just stops down the les as far as the aperture ring allows. If you use an M lens in Av mode then the camera cannot alter the aperture so it treats the lens as if it has one aperture - wide open (even if you set the aperture ring, in Av mode the camera does not stop down). This is not a great issue because in M mode you can use the green button/AE-L or the DOF preview to meter (the camera will stop down the lens to the aperture setting), it is just one more step and no great issue.

I have M and M42 lenses (as well as some A and DA) and I prefer M42 to M lenses. To be honest A is not a great issue to me, I can meter with the camera, so the extra cost of an A lens over an M lens is not worth it - I would much prefer to spend the money on glass: a better M or Tak lens. Note that some M42 lenses need some EV adjustment if used in Av mode, I find that my CZJ Flektogon 35/2.4 meters perfectly on my K100D, but my CZJ Sonnar 135/3.5 needs +1.5EV.

Richard

...and the country is supposed to be heading for a recession, where do people get the money from?

I was watching this:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=140254144195

CZJ Flektogon 35/2.4 with fungus and oil on the blades. I have a Flek (and love it) but the focussing is a bit stiff and the filter thread is knackered so I was hoping to get a spares Flek and swap the body over. But not for 58 quid I won't!

Richard

Excellent points from George, but just one comment:

If you get a lens without an aperture ring your life is made more difficult when reversing the lens. You'll most likely want to use the lens at a small aperture anyway (the default state of a DA lens) for the DoF. However, if you don't have an aperture ring it means that you are constrained to the smallest aperture always and this means that the viewfinder will be dark, and so focusing is difficult, if not impossible. Forget moving the aperture coupler to open the diaphragm because you'll not be able to see what you are pushing (you're looking through the viewfinder) and so you could finger the lens, or worse, since you are close to the subject you're likely to move it (or squah it) with your finger.

So get a 50mm lens with an aperture ring.

Richard

This image shows what appears to be an enormous filter to screw on the front.




It says "smc Pentax PF filter". What is a PF filter?

Richard