Pentax K-M

Hi i have decided to go for a digital SLR i decided on pentax because i have a pentax SF7 SLR with various lenses all work on the KM except my 500 mirror lens it fits the camera but i cant seem to set the F stop all i get in the lcd display is F ---- i have used manual mode is there a way to set the F stop that i have not yet found only had the Camera for a week

Go to the custom menu and look for aperture ring.
Set to enable.

( I am presuming the K-m is the same as most other Pentax cameras.)

Welcome to the forum btw.

Mike's right, have a look from page 240 onwards in your operating manual

Also welcome to the forum

It's unusual for a 500mm mirror lens to have an aperture ring. They are usually fixed at f8 and the F---- indication is indeed correct when a lens of that type is fitted.

You get the F-- because the lens will likely have no electric contacts, they are dirty or the lens is not properly mounted.
On the case of all mirror lenses I know except for Sony's, you do not have an aperture ring.

Good point

Hi My mistake the 500mm mirror lens does NOT have an aperture ring, when i put the lens on the camera all i get is F---- and cannot take any pictures

dispite the fact that the 500 mirror has no aperture ring, you will still need to set the camera to allow use of an aperture ring as described in the manual (I've never used a K-M but there will be one or two custom functions that need setting).

By default the camera will not fire unless it can control the aperture setting electronically. This is impossible with a mirror lens since it has no electronic contacts, so you have to set the camera to allow the shutter to release when no contact is possible.

EDIT: Sorry, what I've written below may only apply to K20D.
EDIT 2: Sorry again, it doesn't normally apply at all. Please see my post on the next page.

That's not quite correct, Mongoose. Setting "Using aperture ring" to Permitted is only required to do two things:

1. Use the aperture ring with a lens with electrical contacts.

2. Stop down metering with any lens.

In M and Av modes, the shutter will still fire with a lens without electrical contacts regardless of the "Using aperture ring" setting.

Padstow, if the lens has no electrical contacts then the camera will always display "F--" because it does not know the aperture. With these lenses you select the aperture via the ring on the lens and use the camera in M with any aperture, or Av mode with the largest aperture.

I think you've got a fixed aperture on your mirror lens, so there's nothing to control anyway besides the shutter speed and sensitivity. You can use M or Av mode as normal.

Sorry for the long reply, but this should help


GETTING STARTED - configuring the camera:
The camera won't allow you to take pictures with manual lenses until you configure it properly. Press the "menu" button, go right until you see the "Custom Setting" menu, and then go down a few menu pages until you see the "Using aperture ring" setting:

At this menu item go right, select "Permitted", and hit the OK button.
Now you can use your manual lenses. Note that this only has to be done once, and there's no need change the setting back again in order to use the auto-aperture or auto-focus lenses. Once you've set it just leave it that way and your camera will happily work with whatever lens you throw at it.
GETTING READY TO SHOOT - mounting a manual lens:
First step (pretty obvious really) is to mount the manual lens on your camera. Nothing special here, manual lenses mount just like automatic ones (with the exception of screw-mount lenses which require an adapter.

The second step is to set the camera to "M" (Manual) mode:
Next, set the focusing mode to "MF" (Manual Focus). There are some options regarding focusing that I'll mention below, but to get started "MF" will work best.

Turn on SR (Shake Reduction) by flipping the switch near the lower-right corner of the LCD:

...and then turn on the camera:

When the camera is powered up with Shake Reduction turned on and a manual lens mounted, it will ask you for the focal length of the lens so it knows how much SR to apply when the camera moves. Use the left/right directional keys on the back of the camera to select the proper focal length and press OK. If you're using a zoom then try to choose a focal length that's as close to what you'll actually shoot with as possible. For example, if you're using an 80-200 zoom at around the halfway point, choose 135mm as the focal length:

You won't see this screen if you turn on SR with the camera already powered up. You can get to this screen by going through the menu screens (it's just about the last item on the "record" menu), but I find it quicker just to turn the camera off and then on again.
And now you're ready to shoot some beautiful photographs with that manual lens!

SHOOTING:
It will take longer to describe this than it does to actually take a shot, so bear with me:
First, set the aperture ring on the lens to the f/stop you will use:

Next, look through the viewfinder and focus:


Half-press the shutter button to turn on the exposure meter:


You can tell the meter is on when the green digits below the viewfinder image light up (there's a menu option that controls how long the meter stays on - use if if the digits shut off too quickly for your taste). Because it's a manual lens, the camera has no idea what f/number you've set it to, so it will show "F(blank)" for the aperture.

And here's the secret to metering with the manual lenses: while the meter is still on, press the "AE-L" button on the back of the camera (it'll probably be very close to where you thumb naturally sits):



When you hit the button the camera will momentarily stop down the lens to take a light reading, then it will set the shutter speed to the appropriate exposure. You'll see the new shutter speed in the green digits below the viewfinder image. After setting the shutter speed the lens will immediately open back up again - the whole thing takes about a second.
If you think the shutter speed is to slow (or too fast!), adjust the aperture (or ISO sensitivity) and repeat (half-press the shutter to turn on the meter and then press the AE-L button to set the shutter speed).

Everything is set, now just fully depress the shutter button to take the picture:




...and that's it! Once you've got the aperture set in the range you want, the only difference between shooting an automatic vs. a manual lens that you have to focus the manual lens manually (duh!) and you have to press the AE-L button to set the shutter speed. And if the lighting conditions aren't changing then you don't even have to do that. In fact, with constant lighting and a subject that stays within your depth of field, you can probably fire shots off even faster than with an automatic lens
MORE ON FOCUSING
One of the interesting things that the camera can do is to "assist" your manual focusing. This is enabled in the custom setup menu ("FI with S lens used"). If enabled, then while the meter is on the autofocus sensor monitors your focusing (using the centre focus point only). When you hit the right focus point the green hexagon below the viewfinder will light up and stay on. I've found that in dim lighting conditions and with fast lenses (ie, 50mm f/1.4), the focus detection is very touchy and seems more distracting than helpful. But if you find it too annoying you can just go back into the menu and disable it again.
If you do enable the focus assist, you can also use what's known as "focus trap" mode. This is enabled by turning the autofocus switch to the "AF" position. Of course the camera can't actually autofocus a manual lens, but in this position it will disable the shutter button unless you've got good focus and the green hexagon is lit in the viewfinder.
You should be able to use this for difficult focusing situations - macros spring to mind. Set the autofocus switch to "AF", frame the subject in the viewfinder, focus as best you can and then hold down the shutter button while slowing moving to and from the subject. With the shutter button held down, the camera will fire as soon as you hit the correct focus point.
It sounds good in theory, although I admit I haven't actually tried this particular technique yet.

SUMMARY
There are a few things that need to be set up, but once that's done it's actually very easy to use manual lenses. Pressing the AE-L button to set the shutter speed is simple to do and faster than mucking about with the shutter speed on my old K1000 and ME Super cameras.
The only caveat is that the smaller APS-C sensor used in Pentax's digital cameras means that lenses have a reduced field of view compared to when they're used on a full-frame 35mm camera. The effect is like multiplying their focal length by 1.5, so that a 50mm lens on a K100 digital camera gives you the same picture you'd get with a 75mm on a film camera. This is a disadvantage if you want to take wide shots, but an advantage for telephoto.

Not with the K10D though... don't know how the other cameras are differend from that but Pentax M lenses refused to work with the camera in M-mode without the setting to premit aperture ring.

I refer the honorable member to K-M instruction manual, Page 79 section C3 item 19,

this is the word of the manual, thanks be to Pentax

The camera will not fire unless it's set to A, or is an FAJ/DA style lens without an aperture ring but possessing electrical contacts. The Mirror lens has no contacts so the Use Aperture Ring setting must be enabled before the camera will fire with that lens attached.

OK, I tested with a K20D - sorry if it doesn't apply to other models. [EDIT: Sorry I am mistaken. Please see my next post]

Padstow, set Allow aperture ring to Permitted.

Interesting that it's different on a K20 compared to all the others, I must admit I was originally working on the assumption that they were all the same as the K10 and only bothered to look it up after you disagreed Iceblinker.

Yes me too and this the first time hearing it and the K20D is already out their quite a long time.