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05-22-2012, 12:49 AM   #1
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Adjusting Flash output.

How do I do it on the built-in flash?

05-22-2012, 01:38 AM   #2
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Which camera body? On my k-7 you push the flash button on the 4 way controller to show the flash settings screen and then turn the rear e-dial to adjust.
I normally only use this if I'm very close to the subject.

Look for 'compensating flash output' in the basic operations section of your manual.
05-22-2012, 12:34 PM   #3
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QuoteOriginally posted by calsan Quote
Which camera body? On my k-7 you push the flash button on the 4 way controller to show the flash settings screen and then turn the rear e-dial to adjust.
I normally only use this if I'm very close to the subject.

Look for 'compensating flash output' in the basic operations section of your manual.
It's the same on K-5.
05-22-2012, 01:36 PM   #4
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Thanks. Will the same procedure work a mounted flash?

06-02-2012, 07:27 PM   #5
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i just tried to do this and ive gotten the same exposure on both -2 and +1... manual mode 125 shutter f8 iso 100. both exposures look exactly the same. am i doing something wrong?
06-02-2012, 09:00 PM   #6
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QuoteOriginally posted by ckswong Quote
i just tried to do this and ive gotten the same exposure on both -2 and +1
If you are using a Pentax A series or above lens, put the camera in P mode and try again.

Also are you using the in-built flash or an external? If it is an external flash, not all of them may support flash exposure compensation.
06-02-2012, 09:06 PM   #7
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wow thats qwirky, so it only works in p mode?
06-03-2012, 06:00 AM   #8
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QuoteOriginally posted by ckswong Quote
so it only works in p mode
Of course not. Flash output adjustment with the built-in flash works in TAv, M etc. The only mode it DOESN'T work in is the green mode. (see p-82 of the K-5 manual).

P mode is just an easy way to ensure that it works for you by minimising your input and letting the camera do the work. So if it works in P mode the problem is not the camera but your equipment (eg a non PTTL external flash) or how you have made your settings.

06-03-2012, 06:13 AM   #9
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QuoteOriginally posted by ckswong Quote
wow thats qwirky, so it only works in p mode?
Can you also answer the questions that rawr asked in post #6 You might get some sensible answers
06-03-2012, 08:23 AM   #10
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using a sigma 18-50 dc lens with bulit in flash. i thought i wrote it down!
06-04-2012, 09:10 PM   #11
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Like Wong, the light output looked the same no matter the +/- setting.
06-05-2012, 12:14 AM   #12
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Huh, I've used before on a K-7 and Pentax lenses with contacts, it works within limits.

If you are too far away no amount of +ve FEC is going to ork

If you are too close and or ISO too high then dialing in -ve FEC wont correct it either.

The built in flash is P-TTL so it tries to expose the subject correctly. If you dial in +1 it tries to expose over by 1 stop. If you dial in -2 it tries to expose under by 2 stops. You are just setting its target exposure not boosting the power.


If the scene is really dark and your manual settings already have the flash P-TTL at its maximum output anyway if you had 0 FEC dialled in then if you turn it up to +1 you don't get more flash the exposure will look the same.

If its really really really dark and to have - 2 FEC dailled in and the flash is still firing at full power to try to give you the result then it will look the same not matter if it is -2, -1, 0 or +1


Put it this way your flash "only goes up to 10". You can't "turn it up to 11"

06-05-2012, 04:27 AM   #13
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How do you override the TTL?
06-05-2012, 04:55 AM   #14
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QuoteOriginally posted by tabl10s Quote
How do I do it on the built-in flash?
Not strictly related to the topic but I found this useful to control the flash output to have some control over depth of field - using P Mode always seems to use the lens wide open with a narrow depth of field.

Use the Guide Number against the ISO to calculate the f stop against distance

i.e.Aperture = ISO Guide Number / Distance in metres

or use the table below which I prepared for my use to enable better control over depth of field.

Use Av or M Mode; the latter allows the ISO, Aperture & Shutter Speed to be set.
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06-05-2012, 06:44 AM   #15
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QuoteOriginally posted by ckswong Quote
i just tried to do this and ive gotten the same exposure on both -2 and +1... manual mode 125 shutter f8 iso 100. both exposures look exactly the same. am i doing something wrong?
I just tried the same thing M mode f8 , 1/125, iso100 in a fairly dark indoor room with a subject at about 4m away. I used a fairly dimly lit room so the ambirnt lighting wasnt too significant in the test.
In my room test at iso100 f8 correct exp is 4seconds so 1/125 is 9 stops underexposed!!

At 4metres all shots with FEC of -2, 0 and +1 look pretty much the same. I went up to 1m from the subject then the flash has more of an effect so the 3 tests shots -2, 0,+1 do differ.



QuoteOriginally posted by WightWalker Quote
Not strictly related to the topic but I found this useful to control the flash output to have some control over depth of field - using P Mode always seems to use the lens wide open with a narrow depth of field.

Use the Guide Number against the ISO to calculate the f stop against distance

i.e.Aperture = ISO Guide Number / Distance in metres

or use the table below which I prepared for my use to enable better control over depth of field.

Use Av or M Mode; the latter allows the ISO, Aperture & Shutter Speed to be set.

I tested at the scene again distance 4m f8 but with iso cranked up to 800 as per this table and the exposure looked much better.


QuoteOriginally posted by tabl10s Quote
How do you override the TTL?
The built in? Well i don't think you can switch off the P-TTL but if you use a lens without contacts (like and "M" or "K" series) it will just fire at full power. You can always short out the contacts on an "A" series or newer with a piece of foil to fool the camera into thinking its an M lens. but that seems to be too much effort. GN of 13 is pretty puny anayway.

Best solution is just to buy an external flash, if it does not have P-TTL (or TTL) capabilities then great just set your power to 1/1, 1/2, 1/4, ......1/128 or whatever. These are cheaper generally

If the flash like most of the current Pentax, Metz, Sigma has all the fancy P-TTL functions or built in lightmeters you can use those in the same way by switching to M mode.
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