Interesting thread; adjusting output on the Pentax flashes

Entropy · 01-03-2011, 02:59 PM

I'm curious - has anyone tried this with a K-7 or (even better) a K-5?

I still need to experiment more, but it seems that on the K-5, my options seem to be "massive overexposure" with no change regardless of trimpot setting for nearly all of the trimpot's travel, except ONE region where major underexposure occurs (maybe where the trimpot is "resetting" since it doesn't have end-stops?)

On the K20 I had consistent change in exposure as I dialed the trimpot CW or CCW until I crossed the "reset point" of the trimpot and started again.

NeverSatisfied · 01-03-2011, 10:48 PM

Originally posted by Entropy

I'm curious - has anyone tried this with a K-7 or (even better) a K-5?

I still need to experiment more, but it seems that on the K-5, my options seem to be "massive overexposure" with no change regardless of trimpot setting for nearly all of the trimpot's travel, except ONE region where major underexposure occurs (maybe where the trimpot is "resetting" since it doesn't have end-stops?)

On the K20 I had consistent change in exposure as I dialed the trimpot CW or CCW until I crossed the "reset point" of the trimpot and started again.

Well that is not encouraging news. I'm hoping to upgrade from my K20D, to a K5 this year... (Though definitely not a deal-breaker!)

Entropy · 01-04-2011, 10:34 AM

Originally posted by NeverSatisfied

Well that is not encouraging news. I'm hoping to upgrade from my K20D, to a K5 this year... (Though definitely not a deal-breaker!)

Don't worry - problem existed between viewfinder and couch. (improper bounce configuration for that room, the camera was able to see direct flash contribution on the ceiling and that FUBARed everything)

The adjustment DOES work on the K-5.

NeverSatisfied · 01-04-2011, 11:23 PM

Cool!

Thanks Entropy!

hoanpham · 01-05-2011, 06:56 AM

Very interesting thread.

I have a few questions:

When you adjust the trimpot, did you have camera body measurement in spot or center weight or average?

I guess that you have a histogram of manual power as reference. As for reference, is it 1/2 power? I am consider +1 as full power.

Entropy · 01-05-2011, 11:29 AM

Originally posted by hoanpham

Very interesting thread.

I have a few questions:

When you adjust the trimpot, did you have camera body measurement in spot or center weight or average?

I guess that you have a histogram of manual power as reference. As for reference, is it 1/2 power? I am consider +1 as full power.

I haven't experimented with the K-5, but my experience with the K10 and K20 was that spot/CW/matrix setting on the camera is ignored when taking flash pictures.

+1 FEC is NOT full power - it's just one stop overexposed if the flash is adjusted correctly. Full power is when the flash is set to Manual and 1/1 power - this trimpot does not adjust that behavior in any way, shape, or form.

Really in my case after I started adjusting, I took a screwdriver around with me and frequently adjusted it until I was happy with where things were landing. Mine may, if anything, be dialed a bit "hot", partly because we have an FEC range of -2 to +1, so there is more room for dialing down a flash that overexposes.

(Previously, my 540 would routinely underexpose even with +1 FEC dialed in.)

hoanpham · 01-06-2011, 12:05 AM

Originally posted by Entropy

partly because we have an FEC range of -2 to +1, so there is more room for dialing down a flash that overexposes.

Ok, I understand.

Originally posted by Entropy

I haven't experimented with the K-5, but my experience with the K10 and K20 was that spot/CW/matrix setting on the camera is ignored when taking flash pictures.

Isn't it a bit wrong when the camera ignore the preflash measurement in p-ttl?

Entropy · 01-06-2011, 08:41 AM - **1 Like**

Originally posted by hoanpham

Ok, I understand.

Isn't it a bit wrong when the camera ignore the preflash measurement in p-ttl?

They don't ignore the preflash measurement - they just seem to ignore the current exposure metering mode when performing the preflash measurement.

May be different on the K-5, but with the 10/20, spot metering on a matte black bag (should result in massive overexposure) produced results no different than matrix metering on a scene with said bag but lots of white.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Very interesting thread from a Nikon->Pentax jumper	jsherman999	Canon, Nikon, Sony, and Other Camera Brands	49	01-13-2010 06:21 AM
Interesting thread reg. K-7's dynamic range	gaddigad	Pentax DSLR Discussion	12	09-16-2009 05:01 AM
What other camera co's flashes can use the same addons as my Pentax flashes?	Grimlock	Flashes, Lighting, and Studio	3	08-22-2008 05:39 PM
Hmmmm...Interesting Canon Thread	benjikan	Photographic Technique	9	06-30-2008 01:53 PM
Adjusting saturation in Pentax K100d	fevbusch	Pentax DSLR Discussion	12	01-27-2007 09:31 PM

01-03-2011, 02:59 PM	#16
Entropy Veteran Member Join Date: Jun 2007 Location: Owego, NY Posts: 976	I'm curious - has anyone tried this with a K-7 or (even better) a K-5? I still need to experiment more, but it seems that on the K-5, my options seem to be "massive overexposure" with no change regardless of trimpot setting for nearly all of the trimpot's travel, except ONE region where major underexposure occurs (maybe where the trimpot is "resetting" since it doesn't have end-stops?) On the K20 I had consistent change in exposure as I dialed the trimpot CW or CCW until I crossed the "reset point" of the trimpot and started again.

01-03-2011, 10:48 PM	#17
NeverSatisfied Veteran Member Join Date: Dec 2007 Location: S.E. Michigan Photos: Albums Posts: 688	Originally posted by Entropy I'm curious - has anyone tried this with a K-7 or (even better) a K-5? I still need to experiment more, but it seems that on the K-5, my options seem to be "massive overexposure" with no change regardless of trimpot setting for nearly all of the trimpot's travel, except ONE region where major underexposure occurs (maybe where the trimpot is "resetting" since it doesn't have end-stops?) On the K20 I had consistent change in exposure as I dialed the trimpot CW or CCW until I crossed the "reset point" of the trimpot and started again. Well that is not encouraging news. I'm hoping to upgrade from my K20D, to a K5 this year... (Though definitely not a deal-breaker!)

01-04-2011, 10:34 AM	#18
Entropy Veteran Member Join Date: Jun 2007 Location: Owego, NY Posts: 976	Originally posted by NeverSatisfied Well that is not encouraging news. I'm hoping to upgrade from my K20D, to a K5 this year... (Though definitely not a deal-breaker!) Don't worry - problem existed between viewfinder and couch. (improper bounce configuration for that room, the camera was able to see direct flash contribution on the ceiling and that FUBARed everything) The adjustment DOES work on the K-5.

01-04-2011, 11:23 PM	#19
NeverSatisfied Veteran Member Join Date: Dec 2007 Location: S.E. Michigan Photos: Albums Posts: 688	Cool! Thanks Entropy!

01-05-2011, 06:56 AM	#20
hoanpham Veteran Member Join Date: Nov 2009 Location: Strand Photos: Gallery \| Albums Posts: 1,366	Very interesting thread. I have a few questions: When you adjust the trimpot, did you have camera body measurement in spot or center weight or average? I guess that you have a histogram of manual power as reference. As for reference, is it 1/2 power? I am consider +1 as full power.

01-05-2011, 11:29 AM	#21
Entropy Veteran Member Join Date: Jun 2007 Location: Owego, NY Posts: 976	Originally posted by hoanpham Very interesting thread. I have a few questions: When you adjust the trimpot, did you have camera body measurement in spot or center weight or average? I guess that you have a histogram of manual power as reference. As for reference, is it 1/2 power? I am consider +1 as full power. I haven't experimented with the K-5, but my experience with the K10 and K20 was that spot/CW/matrix setting on the camera is ignored when taking flash pictures. +1 FEC is NOT full power - it's just one stop overexposed if the flash is adjusted correctly. Full power is when the flash is set to Manual and 1/1 power - this trimpot does not adjust that behavior in any way, shape, or form. Really in my case after I started adjusting, I took a screwdriver around with me and frequently adjusted it until I was happy with where things were landing. Mine may, if anything, be dialed a bit "hot", partly because we have an FEC range of -2 to +1, so there is more room for dialing down a flash that overexposes. (Previously, my 540 would routinely underexpose even with +1 FEC dialed in.)

01-06-2011, 12:05 AM	#22
hoanpham Veteran Member Join Date: Nov 2009 Location: Strand Photos: Gallery \| Albums Posts: 1,366	Originally posted by Entropy partly because we have an FEC range of -2 to +1, so there is more room for dialing down a flash that overexposes. Ok, I understand. Originally posted by Entropy I haven't experimented with the K-5, but my experience with the K10 and K20 was that spot/CW/matrix setting on the camera is ignored when taking flash pictures. Isn't it a bit wrong when the camera ignore the preflash measurement in p-ttl?

01-06-2011, 08:41 AM - 1 Like	#23
Entropy Veteran Member Join Date: Jun 2007 Location: Owego, NY Posts: 976	Originally posted by hoanpham Ok, I understand. Isn't it a bit wrong when the camera ignore the preflash measurement in p-ttl? They don't ignore the preflash measurement - they just seem to ignore the current exposure metering mode when performing the preflash measurement. May be different on the K-5, but with the 10/20, spot metering on a matte black bag (should result in massive overexposure) produced results no different than matrix metering on a scene with said bag but lots of white.