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03-07-2014, 01:44 PM   #1
Pentaxian




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*istDS diopter compensation and pTTL problems

This afternoon I got a *istDS from eBay for (converted) USD 77.
It turned out there are only very view signs of use, and only about 6500 actuations.

But, after 3 hours of troughly testing, I found 2 problems, where the second one may be "a feature, not a bug" (an original Microsoft saying).

1) The diopter compensation has low resistance, and does not change anything. Unfortunately, it is set to a position which doesn't provide a very sharp picture for my eyes. Is there anyone whith experience what kind of defect could it be, and how to repair it for cheap?

2) The TTL mode needs a flash FStop correction of -1, but this is not a problem, as it is consistant for all my 4 Metz and 1 Regula TTL flashes. Even the AF assist light works with the two of the flashes which offer it.
BUT!
I own only one pTTL flash (a Soligor DG-340DZ), which works perfectly with my K200D, including the AF assist.
With the *istDS it does not pre-flash, always uses full power, and no AF assist light. Has the communiction protocol of pTTL changed between the *istDS and the K200D?

EDIT:
To make sure, I now used the Pentax DA 18-55 WR instead the Cosina MC 3.5-4.5/19-35.
With this lens now pTTL works, but it is not very reliable. If I set flash compensation to -1 FStops, two of three exposures are correct, the third is randomly either over or under exposed (same subject, camera not moved). So I may stay with TTL or flash AUTO.
But it is strange, as the Cosina should be FA compatible, and even the Pentax F series lenses do support pTTL.

I have posted the same question in the *ist D sub forum.

EDIT 2:
I forgot to say, before starting serious testing I updated the firmware from 1.00 to 2.02.


03-07-2014, 04:58 PM   #2
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re the diopter, there is a connecting linkage between the adjuster and the diopter that has to be aligned to connect when the top part of the camera body is fitted, so I would say that the top of the camera has been off for some reason and the linkage hasn't been aligned when top was refitted or the linkage is broken. I had to seperate the top case from the body to repair a wiring problem, its not that hard just a few screws, but there is wiring connecting between the two parts so you do have to be careful. The point being when I put it back together I forgot to align the linkage and had to pull it apart again and make sure it connected correctly the second time. Sorry I can't help with the flash issues
cheers
03-08-2014, 01:37 PM   #3
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Original Poster
Thank you.
That's what I thought, too.

I just hope nothing is broken, I am not sure how easy it would be to get the parts.
03-08-2014, 02:05 PM   #4
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Not 100% sure but weren't the *istDS's ttl on the flash not pttl?

03-08-2014, 03:28 PM   #5
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Original Poster
QuoteOriginally posted by kkoether Quote
Not 100% sure but weren't the *istDS's ttl on the flash not pttl?
The *istD, *istDS, and *istDS2 offer both TTL and pTTL. Its contacts are somehow signalling to the flash it can handle both standards.

If an external flash signals it wants pTTL, the camera will automatically work with pTTL and start the communication.

If not, it will work in the old ("legacy") mode, but additionally send the flash-end signal when it has received enough light. If the flash is TTL-capable, it will then shut off the light immediatelly. But as most TTL-flashes also offer Flash auto mode, one can as well switch the flash to "A"; in this case, the flash will just ignore the flash-end signal, and use its own photo cell instead.

EDIT:
TTL is specially interesting when using legacy lenses in connection with anything altering the effective F-stop against the nominal setting, like extension tubes, TCs, and so on.
For ordinary ("real life") flash shots with only one flash the flash auto mode will get you in most cases more consistant results than TTL or pTTL.
And for outside night shots of people any of these methods will give you lots of poor results, as the background will be farer away so the foreground will become strongly over exposed. That's where manual setting and calculations with guide numbers can help. Old hands with experience from the pre-TTL time (seventies) certainly have an advantage.

Last edited by RKKS08; 03-08-2014 at 05:10 PM. Reason: typing
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