Pentax K-7 Flash Problems


pentaxanne

Link Posted 25/03/2010 - 21:04
still getting very mixed and weird results, these were taken in av mode
1st 55mm, iso 250,f10 1/100th sec. auto slow iso


2, av mode no adjustments,18mm f3.5 iso 500 1/50th sec slow auto iso adjustment.


3, av mode no adjustments 18mm f3.5 iso 800 1/50th sec slow atuo adjustment.


even in green mode im getting lots like this, flash power set to o.
Last Edited by pentaxanne on 25/03/2010 - 21:06

Anvh

Link Posted 25/03/2010 - 21:27
You're making it the camera difficult with the dark couch that's also reflective.

What happens when you use spot metering so that just her pretty face is metered?
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 - 21:27

MattMatic

Link Posted 25/03/2010 - 22:03
Anne - can you explain what you'd like to see changed in these images. I think it'll help to understand your expectations

edit: @dlacouture: there's definitely something not right when using f/1.4 The issue seems to almost disappear by f/2.8, but with very wide apertures there's over exposing. I'm testing with the SMC-FA 50/1.4. It would be good to try with the DA*55/1.4... test as follows: point at blank, evenly lit wall (so we can discount metering modes). Set to auto ISO fast, Av mode, normal flash with 0.0Ev compensation. Set f/1.4. Take meter reading. Open popup and read again. I was getting 1/160 & 500iso with no flash and 1/180 & 800iso with flash I'll double check and write a proper report tomorrow.

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 25/03/2010 - 22:36

pentaxanne

Link Posted 25/03/2010 - 23:45
hi stefan and matt sorry the shots are not the best examples,
i have just done some random shots around the house and all shots come out ok(still think the camera bumps the iso up for no reason)
but i think one of my problems in all honesty is i have been usin my d300 for a while and im comparing and prehaps i shouldnt be, the nikon i can set at f10 with a shutter of 320/sec and auto iso 100-1600, and around the house it very rarely goes over iso 800,
example both cameras set on 160/sec f10 nikon selected iso 600, pentax selected 1250.
i found the k7 seems to struggle on faces and almost remove any skin tones when usin flash..
i think my best bet in future is to use full manual iso 100 f8 180/sec


one other thing learnt is either my pentax 50-200mm is longer than 200mm or my nikon at 200mm is more like 150mm.
Last Edited by pentaxanne on 25/03/2010 - 23:52

Anvh

Link Posted 25/03/2010 - 23:51
Seems you have discover a firmware fault in the K-7, what wonderful
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 - 23:55
Anvh wrote:
Seems you have discover a firmware fault in the K-7, what wonderful

i would love to see some sample from people of using the onboard flash stefan, spot metering doesnt seem any different to multi metering,
Last Edited by pentaxanne on 25/03/2010 - 23:55

pentaxanne

Link Posted 26/03/2010 - 00:02
matt is there any specific test you can recomend, i only have to the kit wr lenses at the moment,

MattMatic

Link Posted 26/03/2010 - 10:45
@Stefan - I've haven't told you of the other bug (only little, and carried over from the K20D and K10D)

@Anne - first, some quick comments on the images:
#1: This is as expected. The lower ISO has rendered the ambient area black. There's enough face filling the frame for the camera to take that as the main subject.

#2: Don't forget that ALL cameras meter for mid-grey. So, your dark brown sofa will try to be rendered grey... which means overexposing it.

#3: Partly like #2 - the large dark area is throwing the metering.

Now, as regards your other question... No, you can't experience the bug I related (dlacouture's one) because you'll need a much faster lens. The issue shows up at apertures wider than f/1.8 (as far as I can tell).

Regarding your comment about comparing against the D300 - you're right, you shouldn't The cameras have different algorithms and goals about handling ambient lighting


Here's a setup you can try at home (and hopefully you'll see just how easy it is to gain 100% creative control over the flash lighting - rather than letting the camera make up its mind!).

Position an object in a doorway - a person is good, but they'll get bored. Probably a good idea to sit a doll on a stool (not a chair). You want to be able to see clearly into the room or hall beyond.

Make sure the lighting on both sides of the doorway is about the same.

Ambient: Camera on Av, Auto ISO, set the aperture to f/5.6. Take a meter reading and shot with NO FLASH. For the sake of illustration, let's say the reading was 1/30s, f/5.6, ISO1600

Auto: Now just use the popup - still in Av, Auto ISO. Let's say the reading was 1/60s, f/5.6, ISO200 (let's assume the Nikon auto way of using very low ISO for dark environments). Now - you should see that the room beyond has gone very, very black. Look at the difference in the metering - we have 1Ev in the shutter speed, and 3Ev in the ISO difference making a total of 4Ev underexposure for the ambient. Your subject should look like picture #1

Equal: Now let's use manual mode and set the same exposure as for the Ambient one - e.g. 1/30s, f/5.6, ISO1600. Use the flash. This time you'll hardly notice the flash - except where it has filled in some shadow detail.

Balanced: Again, using manual mode, dial down the ISO by a stop at a time. So, try 1/30s, f/5.6, ISO800 and then ISO400. You should see the room beyond going progressively darker, while the subject in the doorway is getting more prominent and "flashed".

You see, the Pentax will aim more towards the balanced algorithm (which will necessitate a higher ISO), whereas the Nikon is going more towards a full-on flash approach (or so it seems from your comments).


You also need to be aware of this fact:
* Flash exposure does not depend on the shutter speed.

The flash exposure is dependent ONLY on the ISO sensitivity and the aperture. It is the ambient light that is affected by the shutter speed (plus aperture and ISO).

So, when doing manual flash work (as in the "Balanced" experiment) you can work like this:
* Set shutter speed to 1/180s (as a temporary measure)
* Set ISO where you'd like it to be (e.g. ISO200)
* Set the aperture as you'd like (e.g. f/5.6)
* Take your shot and check for flash exposure on your subject only
* With that done, NOW lower the shutter speed to "bring in the ambient" into the composition.
* If you find you need stupidly slow shutter speeds to achieve that, then repeat the cycle but using a higher ISO and/or wider aperture (lower f-number) until you get a balance.

This is actually quite liberating However, it doesn't work too well with toddlers running around.... see how you get on with the above, and if you can cope with more I'll give you at least two ways of dealing with those "ad-hoc" situations.

Hope that helps!!
Matt

P.S. Phew! All that typing... I've almost short-changed myself. Honestly, if you find those insights useful, then do seriously consider purchasing my e-book HERE (there's even more in it!!)
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 26/03/2010 - 10:47

dlacouture

Link Posted 26/03/2010 - 20:58
Anne, something I don't understand is why are you shooting your kid at f/10?

Is that on purpose to stress the flash?

Because it goes against everything I would want as a parent (I usually try to hide my usual junk, huh, decoration, behind some heavy bokeh)...

Also, I'd heavily recommend avoiding to fire a flash head-on into those beautiful eyes... I shot myself once at arm's length for a stupid, engineer-mind-driven reason, and oh my God it hurts (and you see nothing for a full minute afterwards).
(Note : Same thing goes for yourself when blocking the on-board flash with your hand in wireless mode... Watch out for the retina burn!)

Matt, I have the FA50/1.4, and I get the same results (in fact my previous tests were already done on a blank wall).
Last Edited by dlacouture on 26/03/2010 - 21:00

pentaxanne

Link Posted 26/03/2010 - 22:36
thanks matt i will give it a try over the weekend and report back, thanks once again.


dlacouture im just trying different setting and i find f8 f10 seem to give the best exposure, as for hiding my junk i got 4 kids under 5 and they make a mess,
i love to take photos of them and, kids dont stay still so you can't tell them not to look at the flash they just turn at the wrong time.
Last Edited by pentaxanne on 26/03/2010 - 22:38

dlacouture

Link Posted 26/03/2010 - 23:37
4!!! I've got only two (4 and 5) and they are pretty efficient in the chaos dept., so I cannot even start to understand where you still find the time to grab your camera! My photo allocated time slot is usually between midnight and 2 (pretty hard to find interesting subjects!).
[EDIT : I just read my previous post again, and I was of course talking about MY junk only, in case you took it personally... It's only while reading your answer that I got back to your pics and noticed the various baby-related things lying around, got me smiling!]

Kudos to you, Mom!

Can't remember if you talked about hardware, but I quickly invested into a) a fast lens, and b) a P-TTL wireless flash, in order to shoot those pesky little things. This gave me waaaaaay better results than using the on-board flash (which should be restricted by law to wireless controller only, IMO).

Well, anyway, this doesn't solve the auto-iso issue...
They decidedly had problems with this feature, as it's bugged too in P mode (it won't let you select slower shutter speeds once the base iso is reached, whereas it could do so by closing the aperture).
Last Edited by dlacouture on 26/03/2010 - 23:42

pentaxanne

Link Posted 26/03/2010 - 23:52
dlacouture wrote:
4!!! I've got only two (4 and 5) and they are pretty efficient in the chaos dept., so I cannot even start to understand where you still find the time to grab your camera! My photo allocated time slot is usually between midnight and 2 (pretty hard to find interesting subjects!).
[EDIT : I just read my previous post again, and I was of course talking about MY junk only, in case you took it personally... It's only while reading your answer that I got back to your pics and noticed the various baby-related things lying around, got me smiling!]

Kudos to you, Mom!

Can't remember if you talked about hardware, but I quickly invested into a) a fast lens, and b) a P-TTL wireless flash, in order to shoot those pesky little things. This gave me waaaaaay better results than using the on-board flash (which should be restricted by law to wireless controller only, IMO).

Well, anyway, this doesn't solve the auto-iso issue...
They decidedly had problems with this feature, as it's bugged too in P mode (it won't let you select slower shutter speeds once the base iso is reached, whereas it could do so by closing the aperture).

not taken personally my kids do keep me busy i have twins that are a year old. and the others are 3 and 5, and thanks. i have a samsung sef36 pzf flash which can be used wireless which i will have to start using it i think. also invest in some more glass,

pentaxanne

Link Posted 27/03/2010 - 00:01
any tips on usin flash wirless would be great, just set in to channel 1 and the camera set to channel 1 and master, and it does not fire.
Last Edited by pentaxanne on 27/03/2010 - 00:01
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