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10-15-2009, 08:32 PM   #1
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Pentax *istD

I recently switched from my trusty Pentax 35mm SLR to an entry lever Pentax DSLR, an *istD so I was able to utilize my lens collection. I can't seem to get the lightning correct. It seems as if everything is underexposed? Anyone know of this problem/camera combination. Even changing the ISO setting has little effect on light. Thouhgt I did pretty well with my 20+ years of experience now I feel as if I am starting from scratch. Any help is appreciated.

THanks,
Jeff Morgan

10-15-2009, 09:21 PM   #2
Ash
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Hi Jeff.
You have what was once a pro-level camera - very good even in today's standards.
You will have to post some examples, though as it is hard to know what's going on without photos with EXIF data (metadata).

Also tell us what lens you're using on it - are all your lenses giving you under exposure?
Have you tried shooting in different modes to see if the under-exposure is consistent?
10-15-2009, 09:33 PM   #3
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Check it's not set to spot metering.
10-16-2009, 10:36 AM   #4
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I have an *istD and find that it is actually one of the best metering cameras on old lenses, so your problem seems to be a little abnormal.

Here are a couple of things to check,

Unlike some cameras the *istD exposure compensation works in manual mode. Some people question why but it is actually a good thing, because some specific lenses need compensation over the whole range. Your body might have the compensation setto something other than 0. to change, press the +/- button on the upper right corner of the back of the camera, and turn the front thumb wheel.

As mentioned above some lenses (i find screw mount lenses specifically) tend to need exposure correction, and I set the exposure compensation to correct for this, You can also do this, to add or subtract 1-2 stops.

Changing ISO won't change the metereing performance because the meter will know the new ISO setting and apply the same (apparently incorrect) adjustments

When you say the camera under exposes, is this based upon viewing the viewing screen or the histogram? The vioew screen can be a little dark and misleading on th e*istD. You should base everything on the histogram.

To check the metering with your camera, the best way is to focus on a uniformly lit grey surface. I find roads, sidewalks and block walls are the best.

Metering on a surface like this and taking a shot should yeild a photo with the histogram peaking sharply in the middle, or if you are using a photo editor, have an average greysccale value of about 120.

If this checks out, it is just your view screen is dark, and this can be adjusted through the menus, but don't trust this for exposure, use the histogram.

Post some images if you are still having problems

10-16-2009, 02:46 PM   #5
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From a D user

QuoteOriginally posted by jlm2664 Quote
I recently switched from my trusty Pentax 35mm SLR to an entry lever Pentax DSLR, an *istD so I was able to utilize my lens collection. I can't seem to get the lightning correct. It seems as if everything is underexposed? Anyone know of this problem/camera combination. Even changing the ISO setting has little effect on light. Thouhgt I did pretty well with my 20+ years of experience now I feel as if I am starting from scratch. Any help is appreciated.

THanks,
Jeff Morgan
Lowell's advice is good except the D was calibrated to more of a 90 peak in RGB space.... Take a grey card or white wall and the peak will be way to the left of center (90)...
Headroom in Highlights : Where is Zone V in The Digital World? | LibRaw
More in line w/ this:
Current ISO standard, however, recommends that the metering calibration point is less then 18% by half a stop to increase the room in the highlights. The standard suggests 18%/SQRT(12)=12.73%. Adding the slack the standard allows the total headroom is somewhat less then 3 stops, 2.97 eV.
10-16-2009, 04:01 PM   #6
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I confirm this for the *istDS. As soon as I switched to RAW and Lightroom, problem gone.
10-16-2009, 04:08 PM   #7
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QuoteOriginally posted by jeffkrol Quote
Lowell's advice is good except the D was calibrated to more of a 90 peak in RGB space.... Take a grey card or white wall and the peak will be way to the left of center (90)...
Headroom in Highlights : Where is Zone V in The Digital World? | LibRaw
More in line w/ this:
Current ISO standard, however, recommends that the metering calibration point is less then 18% by half a stop to increase the room in the highlights. The standard suggests 18%/SQRT(12)=12.73%. Adding the slack the standard allows the total headroom is somewhat less then 3 stops, 2.97 eV.
interesting point, my comments are based upon actual measurements over many lenses (19 in total) in Adobe color space.
10-16-2009, 04:42 PM   #8
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QuoteOriginally posted by Lowell Goudge Quote
interesting point, my comments are based upon actual measurements over many lenses (19 in total) in Adobe color space.
Which brings us back to the ancient conundrum.... what was the correct metering constant for the D?. Mine would peak at 90. Sent it in for repairs (unrelated) and it came back recalibrated as 90ish.... the old D arguments dating from it's release actually seemed to show 2 calibration standards.. which was extremely odd. Set at 90 my camera had an extremely hard time rendering white white since +2EV was not enough. Won't go into the long history since it really only applies to these "old" bodies.
As to old lenses (which may really not apply to the OP since his collection is undefined) they were variable to a certain degree especially at aperture extremes (fully open or full stopped down) but what the heck. Of course all this is based on only MY sample and is insignificant actually.. not sure you were around for these but it's a somewhat interesting read:
Re: Not quite: Pentax SLR Talk Forum: Digital Photography Review
Are you a 90 or 127.5 Pentaxist?: Pentax SLR Talk Forum: Digital Photography Review
On the Ds:
DS back from repairs, 6 weeks, underexposure problem not fixed!: Pentax SLR Talk Forum: Digital Photography Review
It was an obsession for awhile You may find a few familiar faces here:
To feed your fire: Pentax SLR Talk Forum: Digital Photography Review
My sig quote from Erwin Puts pretty well sums up my feelings on the matter....
'The exposure meter is calibrated to some clearly defined standards and the user needs to adjust his working method and his subject matter to these values. It does not help to suppose all kinds of assumptions that do not exist.'
Erwin Puts

gosh I love that line


Last edited by jeffkrol; 10-16-2009 at 04:54 PM.
10-17-2009, 07:46 PM   #9
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Thanks for all of the advice. It was set to spot metering. Still a learning process. I am going to shoot some test shots to compare tomorrow and update everyone. I currently have 2 Pentax AF lenses, a 28-80 and an 80-200, both of which I have used quite a bit with my ZX-5 film camera and never had any problems. I have been getting an underexposure problem with both lenses in different conditions. Thanks again for the help.
10-17-2009, 08:09 PM   #10
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QuoteOriginally posted by jlm2664 Quote
It was set to spot metering.
I thought so!
Don't feel too bad - I did the same thing last weekend on a bush walk with my K7 - took a lot of interesting photos and only realised the next day why my exposure was all over the place.
10-18-2009, 12:03 AM   #11
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I didn't suspect it, but it can happen to us at the best of times.
In any case, don't be afraid to bump up EC by +0.7 or so to get adequate exposure, and see how you like the results...
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