Pentax *ist DS program modes

[glenn_holden]

I just bought a DS Pentax and I've had it for about a week now. This

is not my first Pentax, I have 5 previous models going back to the

ME super with "program" modes, and in general, they operate the way

I expect them to, in fact there is usually a chart in the back of

their manuals showing how the program modes work.

 

However, there are no such charts in the DS manual and I am a bit

confused by the DS program. For example, in the green smiley faced

mode, it did select a "scenic" when it was obviously a scenic (lens

at 18 mm, focus at 50 plus feet, no motion in the field, etc.), but

it chose 1/350 @ f8 (at 200 ASA). In this mode I would have

suspected the camera to select something like f16 or higher and

lower the shutter speed (as my other Pentax's do).

 

So I tried zooming out the lens to maximum 55 mm (this is the 18-55

mm kit lens) again the camera picked a scenic and the exposure

remained at 1/350 at f8. It seems like the camera ignores the lens

focal length when calculating the exposure.

 

Then I tried a moderate telephoto shot of a sign in the field, the

lens at 55 mm- this time the camera identified it as a portrait

(when the sign was a good 10 plus feet away) and exposed 1/500 at

f8.

 

Then I tried some flowers, the green smiley face recognized this as

a macro "flower" shot, and exposed it as 1/500 @ f8.

 

This is all in the program mode, I checked to make sure it was not

in aperature priority.

 

What is going on here? My local dealer says that they program may be

different than I expect because the "sweet spot" of the lens is

about 2 stops down from the maximum amperature, and with the digital

lens, the focal lengths being smaller than film lens, small

aperatures above f16 are really tiny and lead to pin hole

diffractions, so the program may be trying to keep the aperature

near f8 as possible.

 

Anybody noticed a similiar effect? Yes, I know I can switch over to

Tv or Av, but that is a pain when you are used to the program mode

working more or less as one expects most of the time.

 

All comments welcome.

 

LGH

[derekb]

I don't know the program modes for sure but check out a manual for another simalar programed camera. I use an MZ-6 (ZX=L for US) and it's manual can be downloaded at Pentax Canada's site at:

 

http://www.pentax.ca/support/manual_download.php

 

You could also check on the manual for a MZ-7 (lower model but simalar) or the ist* film camera (also simalar but with newer sensors and body)

 

That should give you some insight. I don't know exactly what my camera is trying to do in the Fully Auto Mode.

 

I suggest Tv or Av modes myself. You will likely feel more at home if you have been a long time film camera user. I am sure you know what you are doing and I suspect like me you don't like the surprises that the program modes provide at times.

 

Thanks!

[molitor]

First of all, I never used the automatic modes. Just did a test for you.

 

If you want the camera to select the appropiate mode you have to set it to "AutoPict" not to the smiley mode. The smiley-mode is only one of the modes of which the camera choses from (apart from night portrait, sports, macro, landscape, portrait). The smiley mode is an universal mode to which the camera will default to if it can not decide which other modes to use.

 

If the camera recognizes the scene as a landscape the mountain will appear in the viewfinder, not the smiley. I get apertures from f11 to f18 in this mode with the kit lens.

[molitor]

Now I did another test in landscape mode and ISO 200 and found out that the camera tries to keep the shutters speed rather high before closing the aperture.

You should repeat your test with a higher ISO setting.

[mdickerson]

Maybe I am confused .. As far as I know the *ist DS does have a regular old program mode, which seems pretty similar to the program curve on my Super Programs; it is the 'P' on the mode dial. Maybe you want to be using that, if you find that Av and Tv are too manual and green 'Autopict' is too clever by half. I've never tried any of the magical-icon modes myself. I wouldn't be surprised if they contain programs that are smarter than me and gave better results, but I guess I feel more like I'm participating if I have to control at least one or two things.

[derekb]

Glen,

 

I just looked at the manuals for the film ist and the MZ-6 film cameras that originated the autopict program modes from a couple of years ago.

 

Both seem to use the same programs and I suspect that yours does too. Please grab either of thier manuals for reference to the program diagrams. Here is an excerpt from both.

[derekb]

Oops wrong format!

[tijean]

Here's a thought:

 

The sharpest aperture on most lenses is between f8 and f11, and both will get everything in focus when focused to infinity or enough in focus that you need not worry about getting the whole flower in focus but that distant tree blurred in as background when hovering over a flower. I usually keep my aperture on f8 in M or Av modes for exactly this reason and maybe Pentax is thinking the same thing.

 

Just a guess.

[glenn_holden]

Thanks folks for all the ideas. I didn't want to respond right away until I ran a whole bunch of tests myself on the weekend.

 

Reinhard, sorry, I did say green smiley face when I should have said green auto pic mode. The green smiley face is on my MZ. I tried several different scenics on the weekend under different light conditions, but I still got the f8, I could not get the f11 to f18 you got until I took the speed from 200 up to 400 then 800 (as you suggested). It seems like it ramps the f stop up once you get between 1/500 and 1/750 shutter speed. By the way, I really had to look hard at shadow details to see any difference between 200 and 400. I sure wouldn't be ashamed of 8 X 10 prints taken at 400 ASA.

 

I also ran a whole series of shots on each of the intelligent modes, at 200 (at 6 megs, highest resolution) and the same shots on Av at f8 for comparison. I used a graphic display monitor we have a work and blew everything up 200 to 400%. Here are my conclusions. The Green Auto Pic mode does more than just adjust the F stop/shutter speed combination. When it selects a scenic, it also appears to add in a step or two of sharpening, I think this is for more detail. When it selects portrait, it seems to put in a bit of softening. When it is in the flower mode, it does boost the color. The manual that comes with the camera does sort of hint at this as well.

 

However, when it is in the good old P mode, it doesn't seem to do any of these cleaver things, just acts more or less as I expect and doesn't add in any sharpening or boost the color saturation, provided you turn off the auto flash. I can post pix if anyone is really interested.

 

Jessica, I suspect you are right about the f8. My camera does tend on automatic to try and stay near f8 to f11. Come to think of it, that probably is the right range of f stop for maximum optical resolution.

 

Sometime this week, I'm going to take some of my other Pentax lens and see what it does using them.

 

Glenn

[david_oswald]

The Smiley mode is equivilant to MTF Program mode, where it balances a lens's optimized MTF data (optimal F-stop, etc) with other factors such as hand-holdable speed, and light conditions.

 

The Landscape mode favors broad depth of field.

The Portrait mode favors narrower depth of field.

The Sport mode favors high shutter speeds, and provides continuous AF.

The Nightshot mode favors slow shutter speeds. It is useful for flash photography where you wish for the foreground to be brightened with flash, and the background to be exposed properly via long exposure time.

The P mode is like Smiley mode, but without MTF balancing.

The Tv and Av modes are Shutter and Aperture priority.

M is metered manual.

AutoPic selects between the other 'pictograph' modes based on the camera's best guess. It seems to be impossible to encourage it to choose sport mode, and it never chooses night-shot mode.