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10-02-2008, 10:22 AM   #1
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HELP PLEASE !!! Bizarre K10d exposure problem!!

ok , so this evening I was trying to take some shots inside the house. with K10D

set 3 rolls of cellophane on a white paper infinity curve on the dining room table.

set up is being done under florescent light from behind me in the kitchen.

I have my Pentax flash mounted wirelessly on a tripod next to me, and 50mm lens on cam on table in front of the rolls.

took flash meter readings, which gave me ISO 100, speed 1/160 , F4.0 - this tested with the flash firing

flash set on full power. manual mode

set my cam to those setting and shot comes out totally black (lens cap was off !! ) - under exposed
test again with flash meter - same reading..

eventually take the cam down to F2.8 1/30, keeping iso 100 - and then pic totally over exposed.

then left ss at 1/30 and went from F2.8 right thur to F22 and every pic is totally over exposed. thats what? a 10 full-stop range??

as soon as I adjusted the ss to 1/40 every shot was under exposed - no matter what F-stop I used !! thats 1-third of a stop between over and under exposure - yet the F's could go thru 10 stops?Huh??

as said, flash was on manual so gave a constant light - it was the ss that gave such dramatic diffs between stops.
2 examples below...





10-02-2008, 10:46 AM   #2
Damn Brit
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There's got to be a simple explanation for this but I'm damned if I can think of one.
Maybe there's a synch problem at that SS. Maybe you were too close, try moving back a bit to see if you can reproduce the effect. Put the flash on the other side.
I don't know mate it's intriguing, I hope someone comes up with an answer.
I don't think exorcism is necessary............................... yet.
10-02-2008, 10:55 AM   #3
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QuoteOriginally posted by Damn Brit Quote
There's got to be a simple explanation for this but I'm damned if I can think of one.
Maybe there's a synch problem at that SS. Maybe you were too close, try moving back a bit to see if you can reproduce the effect. Put the flash on the other side.
I don't know mate it's intriguing, I hope someone comes up with an answer.
I don't think exorcism is necessary............................... yet.
damn gary - i started getting excited reading your reply.. was just about to pack away my book called "How to performs exorcisms, and other Investment advise".. when it occured to me that its not the distant idea...

I tested it in the bedroom straight after by taking a photo and same problem.. exposure settings given my the flash meter were totally under-exposed in the cam...

had to slow down the SS - with the flash to such an extent i could no longer hand hold..

can further add... that approximately 5 minutes after that my battery died completely... wonder if it was a lower power issue??
10-02-2008, 11:01 AM   #4
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Try using a higher ISO. Don't ask me why, it's just a thought. It has to be something simple or, not working properly.

10-02-2008, 11:09 AM   #5
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Am I to understand you are using a flash fired wirelessly. Did you go into the setting on the camera and adjust it to have the flash on the camera fire the flash? Did you set it to custom setting 1 or 2 and now doing something different. I am not at home and so have nothing in fornt of me to look at settings but in my little experimenting yesturday this is a setting issue you are missing. Is the lens manual A or DA? that could be the issue
10-02-2008, 11:20 AM   #6
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using Cactus V2's to fire flash and doing what i have countless times before when i used them ie: same settings. used the DFA 2.8 50mm lens...followed gary's advise and upped the ISO to 400 and have an OK image, but noisy...
totally bizarre that I would need ISO 400 for flash photography?? or could the close distance to subject be the factor after all??
10-02-2008, 11:23 AM   #7
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this is the attempt at ISO 400 and fresh batteries in everything

55mm
iso 400
ss 1/60
F10

HUGE difference !!

10-02-2008, 11:31 AM   #8
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Are you using a Macro lens, is the front element quite deeply recessed, are you using a lens cap?
If you're that close, the way the light is entering the lens could be affected.

10-02-2008, 11:38 AM   #9
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yeah - its the 50mm macro... i think u may be on to something concerning the distance from subject
10-02-2008, 11:53 AM   #10
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ok just did some tests with a range of lenses right thru to the sigma 70 - 300 - and got the exact same results, no matter where i was focusing on..

1/30 totally over exposed..
1/40 totally under exposed..

all irrespective of the F-stop used...


'Houston............. we have a problem !"
10-02-2008, 11:56 AM   #11
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QuoteOriginally posted by StephenG Quote
ok just did some tests with a range of lenses right thru to the sigma 70 - 300 - and got the exact same results, no matter where i was focusing on..

1/30 totally over exposed..
1/40 totally under exposed..

all irrespective of the F-stop used...


'Houston............. we have a problem !"
And it still happens at different distances?
What happens without the flash, do a longer exposure and use a table lamp or something for extra light.
10-02-2008, 12:09 PM   #12
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ok - i think its a problem with the Pentax flash not working wirelessly any more - worked fine last weekend...

tried a different flash, and works perfectly, wirelessly or attached..
tried the pentax attached, and seems to work fine

just took pic of the wife at 4m distance, ss 1/160 and F29 to get proper exposure..
so for some reason, using the Pentax flash attached to the Cactus receiver is just not functioning properly any more..

will have to go back and read all manuals in case there is something I am doing wrong this time, or whether there is simply a compatibility problem!

thanks for trying to help..

so if we wont be having an exorcism tonight..... I got this Investment Bank I can sell you.... really cheap..
10-02-2008, 12:11 PM   #13
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Let me know. I just ordered V2's the otherday and will be using with 540 and Sigma 500. Good luck
10-02-2008, 12:13 PM   #14
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QuoteOriginally posted by StephenG Quote
using Cactus V2's to fire flash and doing what i have countless times before when i used them ie: same settings. used the DFA 2.8 50mm lens...followed gary's advise and upped the ISO to 400 and have an OK image, but noisy...
totally bizarre that I would need ISO 400 for flash photography?? or could the close distance to subject be the factor after all??
Do you have auto EV compensation turned on?
10-02-2008, 12:30 PM   #15
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QuoteOriginally posted by vievetrick Quote
Let me know. I just ordered V2's the otherday and will be using with 540 and Sigma 500. Good luck
I'll have more time to do some more testing on the weekend... stay in touch via PM and i'll keep u posted !!



Venturi - - for some reason that is ringing a bell in my head.... (or the church down the road is at it again!)

ok I'm off to read the manual again to see if its a setting like EV comp that i may have messed around with..

thanks for all the advise.
G'night all !!
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