Pentax smc 1.7 focus problems

I have just been trying out a smc 1.7/ 50mm which I bought a few months ago. My problem is the photos dont seem as sharp as photos taken with the kit lens auto focus which I thought would be the oposite. I also get a window in the screen which can be alterd saying focal lenght 28 30 35 can someone tell me what this meens. Also when I manual focus and get the bleep on from the camera to confirm the focus the shutter does not always fire first time. Can anyone help please.

You have a K100D, right?

Manual, page 47.

Set the camera to MF.

As it says on page 125:

"The shutter cannot be released until the subject is in focus in AF.S"

So even if you had focus confirmation, you've probably moved the camera. Focus confirmation can be very touchy - it only takes a small movement, and it no longer thinks it's in focus.

It's possible that you're mistaking a shallow depth of field for not being in focus, since with a lens with as wide an aperture as F1.7, it won't be sharp over much of a distance close up.

But apart from this, manual focus takes practice if you're not used to it, in which case the AF is likely to be a lot better at focusing than you are.

on start up set your focal length to 50mm. that is for your shake reduction (which you can turn off if you don't need it).

at f1.7 you will not get as sharp an image from that lens as you will when you stop it down a couple stops. (where it will blow away the kit lens).

at f 1.7 you will have very shallow DOF, until you stop it down.

make sure your diopter is set on your viewfinder properly.

use the green focus indicater in the viewfinder.

Should be at least as sharp at F4 (and maybe a bit wider as well) if the lens is clean and in good codition and focused properly.

This is for the Shake Reduction. Scroll right and press OK to select "50" to tell the camera that a 50mm lens is fitted. It can only automatically tell the focal length with more modern lenses. An incorrect length may be contributing the the softness of your images.

You only need to go through the procedure once after the lens is fitted. When turning the camera on next time, you can half-press the shutter button to get rid of the screen. It will remember 50mm.

You may have turned the ring a tiny bit after the camera bleeped, or the camera was slow to bleep (delayed reaction), meaning the lens is incorrectly focused by time you press the button. Look for the green hexagon indicator in the display.

If using MF lenses a lot, you would enjoy a Katzeye focusing screen (if you don't have one already). Actually one is nice to have even when auto-focusing - to check the AF really is working properly.

The window you refer to comes on at start up right? If so this is the camera asking for confirmation of the focal length of the lens in this case 50 (setting can be changed using the left & right keys on the ring around the OK button). This is for updating the camera as to which lens is in use and the for the shake reduction system. The kit lens you use has extra electrical contacts which allows to camera and lens to communicate, where as the older lenses do not.

Make sure that when you are using the manual focus lenses that the camera body is also set to manual focus (MF position), if left on autofocus (AF.S & AF.C) the camera sometimes behaves as you describe, not always firing first go.

Concerning the sharpness issue, assuming the lens is all good, no damage etc, I found that just slow things down little and ensure that your focussing is spot on, what looks OK when quickly viewed sometimes needs a tad adjusted.

Hope this helps.

philstaff

The camera is asking what focal length the lens is for the shake-reduction. Because the lens can't comunicate with the body you need to select 50 and press ok

You have the camera set to AFS. This means the shutter will only fire when the green hexagon is lit (focus confirmation). This can be useful if you have difficulty manually focusing...it is called focus trap. If you set the focus to manual you will be able to fire the shutter irrespective of the green hexagon.

As far as unsharp pictures..... It could be that you had the shake reduction set wrongly ? Or your focusing is not up to scratch ?? Might be the lens is knackered. The only way to test for sure is to set it on a tripod and take lots of test shots. Make sure the SR is off on a tripod. (2 sec timer switches it off automatically.

5 replies in 8 minutes...is this a record ?

Maybe it's a record, but rain stopped play here

Thanks guys for the help but just poped the kit lens back on and now in autofocus the camera will not focus on the subject it is hunting but will not lock on to the subject. I have also tried another lens but same result. Can anyone help not having a great day with my pentax today.

It would help us to help you, you know, if you gave us a lot more information about how you've got the camera set up.

Often, even looking to see how you've set it will prompt you to realise what you've done.

Could be dark, could be a low-contrast subject, could be in AF.C, so focus moving about all the time, could be dirty contacts...

There's almost always a list of things it could be... and if you could narrow it down we'd need to use our mind-reading skills a bit less.

Thanks Chris I have took out the batteries cleaned them and retored the settings in custom settings back to it's default or custom settings and this seems to have done the trick. Im lost as to know why the problem occuerd in the first place but just shot 10 frames and all seems well again.

Back to the origanal question I will take on board all that you have said and try out the lens again thanks again for all your help most kind of you all cheers.

Just another thought I have been told that all lenses have a peek setting were they preform at the best and wonderd if anyone new the best settings for this lens. I know conditions obviously play there part but all being well is there a peek setting the lens works best at giving you the sharpest results.

The rule of thumb is that lenses perform best two stops down from open aperture. In reality, with the 50mm you will have superb performance at most apertures apart from the two extremes.

Just select the aperture you need for DOF considerations.

Thanks for the reply John I think the term used by my freind is the hot spot.