Pentax K-7 Flash Problems


pentaxanne

Link Posted 20/03/2010 - 18:47
hi all i am having problems with my k7 using the flash in tav and user mode, if i select 180/sec f8 using the flash with auto iso its trying to bump the iso up to iso 1600 which is way over expsing it.

if i have it in p mode i can adjust the shutter speed or apature only one at a time, so if i select an apature of f8(ap priority) it selecst the shuter speed of 180/sec and selects say iso 640(in auto 100-1600 iso) cames out ok.

in both modes the shutter speed and apature are the same yet why is it over exposing it so much in user and tav mode.

i even think in the other modes it bumps the iso up to fast using the flash.

any help most greatfully recieved.
Last Edited by pentaxanne on 20/03/2010 - 19:18

johnriley

Link Posted 20/03/2010 - 18:57
Far better to use flash in a more appropriate mode I think.
Best regards, John

pentaxanne

Link Posted 20/03/2010 - 19:00
johnriley wrote:
Far better to use flash in a more appropriate mode I think.

as in what john.

johnriley

Link Posted 20/03/2010 - 19:01
I usually use manual and aperture prioirty modes, both of which are fine. Do make sure though that your ISO setting is not set on auto. I would start with 200 ISO as this seems to be the optimum setting.
Best regards, John

pentaxanne

Link Posted 20/03/2010 - 19:08
johnriley wrote:
I usually use manual and aperture prioirty modes, both of which are fine. Do make sure though that your ISO setting is not set on auto. I would start with 200 ISO as this seems to be the optimum setting.

in manual the iso is only selectable, and taking pics of my kids indoors i need fast shutters speeds hench flash with 180/sec speeds and if i drop the apature more in those modes it will over expose more, just seems abit flawed, my k20d i never had this problem,

Anvh

Link Posted 20/03/2010 - 20:30
pentaxanne wrote:
in manual the iso is only selectable, and taking pics of my kids indoors i need fast shutters speeds hench flash with 180/sec speeds and if i drop the apature more in those modes it will over expose more, just seems abit flawed, my k20d i never had this problem,

In what mode, flash and camera???
If you use it in manual and you open up the aperture then of course more light comes in ambient and flash if the flashpower doesn't change that is.

As for the shutter-speed if your flash is powerful enough you can use shutter speed of 1/10 and get perfectly sharp photos as long as the flash overpowers the ambient light a lot. the flash only takes 1/10.000 of a sec the rest of the shutterspeed is only controlling the amount of ambient light hitting the sensor, makes sense?

But we really need to know more to help you.
What flash are you using and in what kind of conductions, indoor in a room in a big hall, outdoors?
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Last Edited by Anvh on 20/03/2010 - 20:31

pentaxanne

Link Posted 20/03/2010 - 20:53
Anvh wrote:
pentaxanne wrote:
in manual the iso is only selectable, and taking pics of my kids indoors i need fast shutters speeds hench flash with 180/sec speeds and if i drop the apature more in those modes it will over expose more, just seems abit flawed, my k20d i never had this problem,

In what mode, flash and camera???
If you use it in manual and you open up the aperture then of course more light comes in ambient and flash if the flashpower doesn't change that is.

As for the shutter-speed if your flash is powerful enough you can use shutter speed of 1/10 and get perfectly sharp photos as long as the flash overpowers the ambient light a lot. the flash only takes 1/10.000 of a sec the rest of the shutterspeed is only controlling the amount of ambient light hitting the sensor, makes sense?

But we really need to know more to help you.
What flash are you using and in what kind of conductions, indoor in a room in a big hall, outdoors?

built in flash, in my house, havent even played with other flash yet.
which is a samsung same as the pentax 360.
Last Edited by pentaxanne on 20/03/2010 - 20:57

Anvh

Link Posted 20/03/2010 - 21:29
Build-in flash isn't very powerful, it might be it was hitting the limit of would it could do and came to the correct exposure when you use a larger aperture. Only speculating here.

With the build- in flash and with the Samsung flash simply use Manual mode for your camera and P-TTL mode for your flash.
The P-TTL will make sure the exposure will be correct, if the flash is powerful enough to do that.

In Manual mode you've 3 ways to control the photo with a flash.
Shutter-speed = controls the amount of ambient light in your photo flash light stays the same. So if the flash is very hard in the photo you can soften that up for example by using a longer shutterspeed or you control the background with that. The flash does not reach all that far and gets weaker the father away it gets so a background needs to have it from the ambient light, with the shutterspeed you control that.
ISO + Aperture = controls the flash light and ambient light, if the flash takes long to recharge or your photo is under expose you need to use a bigger aperture or higher ISO.

In very shot.
Shutter-speed = balance between ambient & flash light.
ISO/Aperture = Exposure ambient & flash

Now I'm forgetting flash power but P-TTL mode will take care of that if it works correctly.

This applies for everything indoor, outdoors it does not matter.

This might not help you much so I'll just tell you how I shoot indoors with a flashgun.

-Camera-
Manual mode
1/100 shutterspeed (don't ask me why see what works for you)
Aperture f/4 is good for portraits if you can't make it use the lens wide open.
ISO 200 and if the flash does not recycle fast enough ISO400

-Flash-
P-TTL mode
Aimed at the ceiling if you can do that for softer light.
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Last Edited by Anvh on 20/03/2010 - 21:29

pentaxanne

Link Posted 21/03/2010 - 00:12
just tried on full manual with built in flash, set shutter speed 160/sec f5.6 iso 400,lens set at 200mm subject about 6.5ft away
come out good adjusted to f8 come out slightly darker as expected.

same test again but with samsung sef36 pzf flash(same as pentax 360)
set on green pttl, at f5.6 its under exposed but if i use f8 or f10 the exposure is alot better(how does that work)
also its the first time i have noticed that the flash does not want to zoom past 58mm (not noticed it with the k200d and k20d)

oh and why oh why did pentax use a black hot shoe(only put the flash on 3 times and it marked already)
Last Edited by pentaxanne on 21/03/2010 - 00:14

Anvh

Link Posted 21/03/2010 - 20:22
yeah don't know about the hotshoe, with the lower end models they are clear metal I believe, or at least with the K-X that is.


P-TTL is not known for his consistency and is sensitive for reflections, you might want to try spot-metering on the camera and see if it behaves a bit better.

But what you're saying is quite strange though because I've read quite some posts that users found that P-TTL was improved with the K-7.
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ

golfdiesel

Link Posted 21/03/2010 - 21:44
I prefer to use full manual mode when doing flash photography or I use the flash in 'A' mode so the flash decides when there is enough light en not the camera which does not seem very good at that task (at least the K20D isn't)
Camera:K20D|Ist*DS|Spotmatic II|MZ-10
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T

dlacouture

Link Posted 22/03/2010 - 22:25
Well, I've made some tests, and I agree, the behavior is not that logical on the k7...

For instance, in a tungsten-lit room, Av mode set to f/1.4, Auto-iso on Slow :
* Flash off, it reads 1/40, iso 400...
* Flash set to normal, it reads 1/100, 800 iso...
* Flash Set to Slow, it reads 1/80, 800 iso

So, it bumps the iso up for no real reason...

Worse, with Auto-iso set to fast, you have the following:
* flash off, 1/160, 1600 iso (in line with the previous 1/40, 400iso)
* Flash on, 1/90, 3200 iso.

So, you end up with nearly a +2Ev overexposure without even having fired the flash!!!

Behavior with auto-iso disabled seems a little more logical, so I think Auto-iso does not really support P-TTL flash...
Last Edited by dlacouture on 22/03/2010 - 22:28

pentaxanne

Link Posted 22/03/2010 - 23:32
dlacouture wrote:
Well, I've made some tests, and I agree, the behavior is not that logical on the k7...

For instance, in a tungsten-lit room, Av mode set to f/1.4, Auto-iso on Slow :
* Flash off, it reads 1/40, iso 400...
* Flash set to normal, it reads 1/100, 800 iso...
* Flash Set to Slow, it reads 1/80, 800 iso

So, it bumps the iso up for no real reason...

Worse, with Auto-iso set to fast, you have the following:
* flash off, 1/160, 1600 iso (in line with the previous 1/40, 400iso)
* Flash on, 1/90, 3200 iso.

So, you end up with nearly a +2Ev overexposure without even having fired the flash!!!

Behavior with auto-iso disabled seems a little more logical, so I think Auto-iso does not really support P-TTL flash...

thanks i thought it was me, i have tried so many different things and keep coming up with the same results.

i had a play again tonight and shots taken at f8 shutter speed 100th sec, and it puttin the iso up at 1000, the same shot using full manual iso 100 is spot on, also if at f8 50mm s/s 100th sec the iso will be say 1000 but if i zoom to say 200mm the iso drops down to 500 which will be underexposed but if i setn it manual it needs iso 1000.
i even get dodgy results in av mode as soon as i up the f stop it just wants to bang the iso up to 1600,
so i think its gonna have to be full manual from now on, abit of a pain.
Last Edited by pentaxanne on 22/03/2010 - 23:36

Anvh

Link Posted 23/03/2010 - 00:48
Anne like dlacouture say don't use auto-iso and it will go better.
And like I said just use Manual mode of your camera and use the flash in P-TTL, the flash will then provide for the auto-exposure.
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ

pentaxanne

Link Posted 23/03/2010 - 17:50
hi stefan i understand that it will work in full manual, but if i let anyone else usees it they will not be able to use the flash which i think is very poor, also the fact i paid 900 for a camera that needs to be used in full manual to get the flash to work properly.
even with the samsung sef 36pzf flash (pttl compaitable) result are dodgy.
i never had this problem with the k20d and k200d
and im not the only one with this problems it seems.

if a mod reads this can he/she change the title to pentax k7 flash problems. thanks
anne
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