Pentax K-7 Flash Problems


pentaxanne

Link Posted 24/03/2010 - 23:26
after having a play im still convinced that the camera is upping the iso up for no real need even with slow adjustment selected., a shot that can use iso 100 with no problem and its using iso 1600,
Last Edited by pentaxanne on 24/03/2010 - 23:44

pentaxanne

Link Posted 25/03/2010 - 00:05
also when using av mode with the lens at 200mm about 8ft away from the subject with a shutterspeed of 180/sec and iso 400 and f4.5 it comes out slightly darker than the same test with an apature of f8 surely the larger apature should be brighter.

Anvh

Link Posted 25/03/2010 - 00:16
I can't comment on the iso.
What do you mean with slow adjustment selected, if you mean trailing curtain than that's your problem. When you've you flash set on trail curtain, the camera will keep on metering normally.

It's the symbol with two arrows and a flash on the right side.

pentaxanne wrote:
also when using av mode with the lens at 200mm about 8ft away from the subject with a shutterspeed of 180/sec and iso 400 and f4.5 it comes out slightly darker than the same test with an apature of f8 surely the larger apature should be brighter.

Because of the P-TTL metering the camera automatically adjust the flash power and therefore the exposure.
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 25/03/2010 - 00:19

pentaxanne

Link Posted 25/03/2010 - 08:46
hi stefan what i mean by slow adjustment is that the k7 has a setting for the iso to bump it up faster or slower it has 3 setting slow normal and fast.
Last Edited by pentaxanne on 25/03/2010 - 08:47

MattMatic

Link Posted 25/03/2010 - 10:05
@Stefan: The K-7 introduced a new option for the Auto ISO. There is now "Slow" (which will veer towards lower ISOs but obviously slower shutter speeds), "Normal" (which is what the K20D and K10D do), and "Fast" (where it'll use higher ISOs to gain a faster shutter speed). A bit like a program-line for ISO. Useful

@Anne: Ok, from using my K-7 I can say there isn't a problem with the flash - it works exactly as I'd expect. The way the ISO is bumped up is what I would expect... at least on my K-7

Quote:
also when using av mode with the lens at 200mm about 8ft away from the subject with a shutterspeed of 180/sec and iso 400 and f4.5 it comes out slightly darker than the same test with an apature of f8 surely the larger apature should be brighter.

No, if anything I'd expecit it to be the same. I presume you are forcing the aperture and shutter speed and expecting a difference in exposure when using the flash? Actually, with low ambient light I would expect the flash to compensate and make them pretty much the same. If you are experiencing a slightly darker image at f/4.5 when using 200mm, I would probably put it down to lens vignetting

I would suggest that there is some basic photographic technical knowledge that would help - shutter speeds, apertures, ISO sensitivities etc.


For indoor "point-and-shoot" flash photography I would suggest the following:
* Manual camera mode
* Fixed ISO, e.g. ISO 400 or 800
* Fixed aperture, e.g. f/8
* Auto flash (though personally I'd use a flash Ev compensation of between -0.5 and -1.0)
(The flash will do all the donkey work of getting the exposure right)

You could set this up on the "USER" setting.

If you want to reduce the "blam" effect of the flash then I'd suggest the following for indoor, low light photography:
* Av camera mode
* Higher ISO, e.g. ISO800 or ISO1600
* Fixed aperture, e.g. f/5.6 (but be more careful with focussing)
* Flash set to "Slow, trailing curtain sync"
Here, the shutter speeds will be much lower - and you'll get some blurring - but the flash will "freeze" the motion. In this setup the ambient light and the flash light will be equally balanced, so you will have less of a harsh image.


If you want to balance the ambient light and flash:
* Manual camera mode
* Higher ISO, e.g. ISO800 (unless you're using a tripod)
* Choose an aperture and shutter speed that register about -1 to -1.5 Ev on the meter
* Flash (P-TTL or popup)
Here, the ambient light will just shine through, but the flash will be dominant. With careful choice of aperture, shutter speed, and ISO you can usually get something that will be ok for kids. The resulting image will be better than either of the above - you'll preserve the "feel" of the room, but make use of the flash.

(I cover these steps and more in my 4.95 flash guide )


In reality, the camera can't automatically "know" which of these three you're aiming for. All cameras, on auto, will just do a quick judgment. The Nikons will add distance information into the flash auto calculations - and this certainly helps (because the effectiveness of the flash will quarter for every doubling of distance - the "inverse square law"). Although Pentax system doesn't have this distance information as you've already experienced with the K20D Pentax can do flash just fine.


Looks like we're folding in multiple "issues" into this one thread...

I'm still trying to work out what you had wrongly set

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 25/03/2010 - 10:05

pentaxanne

Link Posted 25/03/2010 - 10:38
hi matt will read properely when i get 2 mins. I was expecting the same exposure. And in the test with the pop up and the samsung why is the samsung not so bright. I find using manual f8 shutter speed 180/sec iso 100 is fine for most shots. It tends to be to bright on people faces otherwise

Anvh

Link Posted 25/03/2010 - 10:54
MattMatic wrote:
@Stefan: The K-7 introduced a new option for the Auto ISO. There is now "Slow" (which will veer towards lower ISOs but obviously slower shutter speeds), "Normal" (which is what the K20D and K10D do), and "Fast" (where it'll use higher ISOs to gain a faster shutter speed). A bit like a program-line for ISO. Useful

I cover these steps and more in my 4.95 flash guide

Indeed handy

Can we expect an update for your book now that you have a K7?
Stefan


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

pentaxanne

Link Posted 25/03/2010 - 10:58
also i noticed this morning that the samsung flash is not zooming past 58 in auto if i manual do it its goes to 85. Is this the pttl causing this

Anvh

Link Posted 25/03/2010 - 11:02
hmmm what happens when you use manual zoom, can you get it on 85mm then?
Also is your flash not set on 465 or 6x7?
Stefan


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

MattMatic

Link Posted 25/03/2010 - 11:05
@Stefan - probably (Depending on time, health and energy - all three lacking at the mo')

@Anne - the AF360 was built pre-digital and the angle display is slightly confusing (but not incorrect). 58 on the AF360 is 85mm on the camera (because 85mm on an APS digital is approx 58 * 1.5
http://www.mattmatic.co.uk
(For gallery, tips and links)

pentaxanne

Link Posted 25/03/2010 - 11:20
hi stefan it is set to 35mm and i will try set at 85mm tonight and see what it does. Matt i didnt realise that the samsung sef 36pzf was built before digital i suppose the 35mm should have give it away. Thanks

Anvh

Link Posted 25/03/2010 - 11:27
MattMatic wrote:
@Stefan - probably (Depending on time, health and energy - all three lacking at the mo')

@Anne - the AF360 was built pre-digital and the angle display is slightly confusing (but not incorrect). 58 on the AF360 is 85mm on the camera (because 85mm on an APS digital is approx 58 * 1.5

Take your time Matt, I don't think much has changed.

You could be right about the AF360, i thought it would show 85mm because it was set on 35mm format.

Anne, I've the AF540 which has the same zoom range as the AF360 but can go digital.
Digital goes from 16mm till 58mm
35mm goes from 24mm till 85mm
I hope that help for you to check things out.
Stefan


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

dlacouture

Link Posted 25/03/2010 - 15:47
Matt, did you try with a fast aperture? See my first post, I found that the k7 just upped the iso with no real reasons...

MattMatic

Link Posted 25/03/2010 - 15:53
@dlacouture: I'll check later and see if I can work out what the K-7's algorithm is
http://www.mattmatic.co.uk
(For gallery, tips and links)

MattMatic

Link Posted 25/03/2010 - 16:18
Only have an f/2.8 lens to hand where I am...
My K-7 behaves exactly as I'd expect.

e.g.
Auto ISO 100-1600, Slow, Av mode, Flash set to normal, 0.0Ev.
No Flash: f/2.8, 1/60, ISO640
Flash: f/2.8, 1/160, ISO160 (yes, 160, not 1600)

Auto ISO 100-1600, Fast, Av mode, Flash set to normal, 0.0Ev.
No Flash: f/2.8, 1/160, ISO1600
Flash: f/2.8, 1/160, ISO640

I can't make it do what yours is doing! Odd
Maybe there's a custom setting we have set differently??

Which lens do you have?

I'm sure there must be an explanation.
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Add a Comment
You must be registered or logged-in to comment.