istDS - What they don't tell you.

Having been a Pentax user for many years and having several older K mount lenses, when I decided to purchase a digital SLR I was attracted to the istDS by many reviews stating that the older K mount lenses could still be used with it. However I have now found that you can only use these older lenses at fully open aperture as they will not stop down automatically. Having taken two completely white pictures using flash I decided to contact Pentax for information and was told "Yes you can use these lenses but only at full aperture - you set the exposure with the shutter time" !!! What a let down !!!. My final question is 'do you in that case get any indication in the viewfinder that correct expose is set '?

Hi,
I don't think this is the case. I will leave it to one of the experts to tell you how to do it but it may involve a firmware upgrade and does involve setting thing in the menu.

regards
Kim

This point was raised in the *istD/DS Yahoo group and this reply was posted:-

'I am a new member. My name is Dennis Simmons, born in the UK but now living in Brisbane, Australia. I joined the group as I was considering purchasing the *ist DS for use with my old K Mount, non-A and A lenses and wanted to read of users experiences with their older lenses. The information I found helped me purchase the camera – thank you! My main use of the camera will be for astrophotography through my 4” refractor which has a computer controlled mount that tracks the stars to compensate for the rotation of the Earth. This will allow me to take long exposure images of galaxies, star fields and nebulae.



I’ve had my Pentax *ist DS for a week now and the lack of favourable conditions has prevented me from using it for astrophotography – sigh! After much playing indoors, I thought that I would share my early findings on the functionality of older K mount lenses, as I found the manual a little unclear and somewhat difficult to follow on this topic. Here are some of my observations. Where possible, I have included a reference to the relevant page (Pxxx) in the Pentax *ist DS manual.



TEST 1 – PENTAX K MOUNT 35mm FILM LENSES NON “A”.

For this test, I used the following lenses (year of purchase):

Pentax 50mm f1.8 (1976) as provided with my original Pentax KM
Pentax 135mm f2.5 (1990)
Tokina 500mm f8 mirror lens (1990)


User Modified settings:

To obtain manually focused and correctly exposed images, I had to change four settings (2 hardware, 2 software) as follows:

Setting 1: On the camera body, set the Focus Mode Lever to MF (P121).

Setting 2: In the [C Custom Settings] menu (P100/101) toggle the option “Fl with S lens used” from the default of “1 Unavailable” to “2 Available”

Setting 3: In the [C Custom Settings] menu (P100/101) toggle the option “Using aperture ring” from the default of “1 Prohibited” to “2 Permitted”

Setting 4: Set the Mode Dial (P104/105) to M for Manual.

When scrolling the [C Custom Settings] menu, the options toggled in Settings 2 & 3 above are the first two lines on the 3rd screen (of 4).



Procedure for taking a picture:

With the above 4 settings in their changed state, do the following:

(a) Dial in the aperture manually on the aperture ring of the non A lens (e.g. f

(b) Compose the image.

(c) Manually focus through the viewfinder.

(d) Half depress the shutter release and hold (illustration on P45).

(e) Press the “AE-L” button and you should hear a noise associated with the iris being manually stopped down (the viewfinder darkens momentarily) as the meter takes a reading.

(f) Now fully depress the already half depressed shutter release.



Congratulations – you have just taken a manually focused, correctly exposed image!



Notes:

1. Every time I forgot to press the AE-L button (step (e) above) to manually cause the iris to be stopped down for metering, the resultant image was totally overexposed i.e. a white screen.

2. In the viewfinder, F - - is displayed for the aperture value regardless of what aperture you have manually selected.





TEST 2 – LEICA SPOTTING SCOPE WITH “T” RING

By following the same procedure as above (except that the aperture in not adjustable) I was able to obtain sharp, correctly exposed images by using the Leica photo-adapter and a T ring.





TEST 3- PENTAX K MOUNT 35mm FILM LENSES WITH “A” SETTING.

For this test, I used the following lenses (year of purchase):

Vivitar Series 1 70-200mm f2.8-4 (1990)
Sigma 400mm f5.6 (1989)
Sigma 24mm f2.8 (1992)


Notes:

1. With the aperture ring set to A, the above lenses could be manually focused. The shutter speed and aperture values were displayed in the viewfinder.

2. There was no requirement to press the AE-L button for stopped down manual metering, as the camera could read the values when the lens aperture ring is set to the A position.

3. If you forget to set the Focus Mode Lever to MF, the shutter will not fire.





CONCLUSION:

So, there you have it. It seems that Pentax has indeed maintained backward compatibility with older K mount lenses. All I need now is some good weather so I can test the camera on my Vixen 4” refractor. Please note that the above information is for guidance only and is the result of an afternoon playing with the camera, it may contain errors and misunderstandings.



OTHER FINDINGS:

1. There is a poor man’s mirror lock up (P55) accessed by using the Function Button to set the Self Timer to 2 seconds. When you release the shutter, the mirror flips up and then after approximately 2 seconds, the exposure is made.

2. My old Pentax right angle viewfinder will not attach to the *ist DS, even with the rubber eye guard removed – oh well.



Cheers



Dennis'

Cliff

Many thanks Clif. I will give that a try and let you know how I get on.

Regards Dennis

Can anybody explain what this setting actually does ?

I've looked at the menu on the camera, which explains that when an 'S' mount lens is used (by which, I assume, they mean screw lens) you can toggle between the focus indicator being available or not available

*ist-DS manual, page 101:
I think what they're getting at is that if you enable "FI with S" then the body thinks there's always a lens connected and will try to show whether it's in focus. If you don't have screw thread lenses, then disable this - it will detect whether you have a lens connected.

Matt

Sort of connected to this, don't forget that if you have a manual focus lens fitted to AF bodies and the body is set to AF then the shutter will only release when the in focus indicator is OK. If you don't want to be limited in this way, set to MF.

This caused one or two people I know quite a bit of puzzlement for a while, it's the simple details that get us foxed!

I have conducted cliff_occo's experiment on my own istDS setup and can see no difference between the 'FI with S lenses' setting (Test 1, setting 2 above ) being either on or off. All of my lenses are K mount (mix of M, A, FA) so I can't test the difference using a screw lens. If the 'S' in 'FI with S' means screw, i wonder why it isn't shown as 'M42'. I'm wondering if the 'S' stands for 'Soft' (as in the series of soft lenses), Focus Indicator when Soft lense are used kind off makes a bit more sense to me. In his experiment, Cliff suggests using the AE-L button to set shutter speed according to the manually selected aperture, which is quicker and simpler than using the 'preview and manually adjust shutter in metered manual mode' method.

I just found page 101 in the manual which states 'S' means screw fit. Ignore my last post, I promise to do read more thoroughly or 'engage manual before typing rubbish'.