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09-26-2012, 11:31 PM   #1
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K-5 and PTTL bounce flash--any success stories?

I just bought a K-5 and now find that the bounce flash exposure with my older AF-360FGZ flash is terrible. It's a bummer because the camera is just so much better in every other way than my old Canon T1i. I find P-TTL bounce to be very unpredictable, mostly seriously overexposed, and somewhat linked to zoom range (with the 18-55 kit lens). My tests shots are using manual mode, ISO 200, 1/60, f5.6, exp -3.0. Direct flash seems mostly ok.

There doesn't seem to be any resolution despite the many threads and theories about this problem. Are there any strobists that have had consistently good results with K-5 and 360FGZ (or other) bounce flash? Anyone have initial poor bounce results with their K-5 that was solved by purchasing a new or different model flash?

I will be doing some work at an indoor event and don't want to bring my Canon! Thanks!

09-27-2012, 01:13 AM   #2
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How far away is your subject?

If you're shooting manual, you're telling the camera that you know the correct exposure - by shooting manual, you don't give the camera the chance to rescue the shot for you!

In fact the AF360 manual says this:
"The amount of light during bounce flash photography is greatly affected by the condition of the reflective surface, therefore test pictures should be taken beforehand or changing the exposure and taking several pictures may be recommended"

I normally shoot in either Av or Tv mode when using the flash - it gives the camera the latitude to adjust either aperture or shutter speed to rescue the situation.

If you're over exposed, then try shooting in Tv mode at 1/180th - the camera can then close down the aperture if the shot is still going to be over exposed.

Plan B would be to switch to HSS.
09-27-2012, 01:43 AM   #3
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I use Metz 48 AF1 bounced with the K5 and have no problems with this combination, given there is good contact between the camera and the flash - make sure the flash`s autofocus assist light goes on instead of the camera`s

nearly all pics shot with the Metz 48 AF1 + diffuser, tilted upwards at 45, K5 + DA 15/4, DA 35/2,8 macro and DFA 100/2,8 macro WR
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09-27-2012, 03:18 AM   #4
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I was recently shooting in a warehouse, bouncing the 540 up off the roof, (10metre ceiling) and it worked a treat, with a sigma 12-24mm, Pentax 10-17, and Sigma 8-16.

I also use it mounted in an umbrella , reflecting, using the P=ttl lead, again, perfect exposures for product shots.

cmohr

09-27-2012, 05:27 AM   #5
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Dial down the exposure on the flash (Page 82 in your manual) - its a different setting than the EV comp and has a range of -2 - +1. EV comp wont work in flash situations because exposure is aperture controlled - changing shutter speed doesn't affect the result - it just makes the back ground darker (areas in the fall off).

Also, shooting at ISO 200 doubles the guide number of the flash right? - I almost always shoot at ISO 100 (though I am working on a Kr).

I'm no strobist by any means, but I've not had any over exposure issues, well, besides getting caught in environments where my chosen aperture and 1/180 permits over exposure of the scene (like fill flash in outdoors)

Good luck
09-27-2012, 06:32 AM   #6
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QuoteOriginally posted by pentrax Quote
I just bought a K-5 and now find that the bounce flash exposure with my older AF-360FGZ flash is terrible. It's a bummer because the camera is just so much better in every other way than my old Canon T1i. I find P-TTL bounce to be very unpredictable, mostly seriously overexposed, and somewhat linked to zoom range (with the 18-55 kit lens). My tests shots are using manual mode, ISO 200, 1/60, f5.6, exp -3.0. Direct flash seems mostly ok.

There doesn't seem to be any resolution despite the many threads and theories about this problem. Are there any strobists that have had consistently good results with K-5 and 360FGZ (or other) bounce flash? Anyone have initial poor bounce results with their K-5 that was solved by purchasing a new or different model flash?

I will be doing some work at an indoor event and don't want to bring my Canon! Thanks!
I use the AF540, but the problem is the same as you describe. Some say turning on the highlight correction helps. I am not convinced of that.

In my experience, the problem crops up mainly when shooting in bounce and a reasonably large area of the scene is white or light colored. I can absolutely make this happen by simply shooting a subject with little or no light colors and the shooting the exact scene with a subject wearing a white or light colored shirt.

I have been experimenting with Tav mode and flash recently, mainly as outdoor fill, but I hope to give this mode a try indoors with bounce to see if it helps.

Otherwise, I just try and dial the flash comp down when there is a significant light colored area in the scene. The good news is that the K5 DR is so good that in most cases you can get away with leaving some negative flash comp dialed in always and just boost the under exposure in normal scenes a bit in PP.

Ray
09-27-2012, 07:46 AM   #7
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QuoteOriginally posted by mattt Quote
Also, shooting at ISO 200 doubles the guide number of the flash right? - I almost always shoot at ISO 100 (though I am working on a Kr).
You need to quadruple the ISO to get double the distance. Because of the square law you need 4 times as much light to reach twice as far. So you either quadruple the amount of light from the flash or quadruple the ISO you are using.

Greg
09-27-2012, 08:04 AM - 1 Like   #8
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Mine seems to be working...I did have some problems with the flash not making contact correctly in the hotshoe (and the flash would show ttl instead of p-ttl and nuke the scene). A quick cleaning of the contacts and it worked in P-ttl the rest of the time.







09-27-2012, 08:09 AM   #9
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QuoteOriginally posted by Ray Pulley Quote
I use the AF540, but the problem is the same as you describe. Some say turning on the highlight correction helps. I am not convinced of that.

In my experience, the problem crops up mainly when shooting in bounce and a reasonably large area of the scene is white or light colored. I can absolutely make this happen by simply shooting a subject with little or no light colors and the shooting the exact scene with a subject wearing a white or light colored shirt.

I have been experimenting with Tav mode and flash recently, mainly as outdoor fill, but I hope to give this mode a try indoors with bounce to see if it helps.

Otherwise, I just try and dial the flash comp down when there is a significant light colored area in the scene. The good news is that the K5 DR is so good that in most cases you can get away with leaving some negative flash comp dialed in always and just boost the under exposure in normal scenes a bit in PP.

Ray
Ray's right here, I find best results in M to be honest (and would avoid TAv which seems a poor choice for flash in my experience).

I've found that the bounce flash with both my AF360 and 540 has a minimum power output that is too powerful for some combinations of aperture, iso and distance. This doesn't tend to happen easily with direct flash, which (it seems) can give a much smaller minimum flash power if needed.

This is, as pointed out, a bigger issue where there is a lot of reflection/white areas at close quarters. Ray's approach is sound in that -2EV FEC where you have white objects will usually give a good result (or at least one that can be PP'd).

So far I really did NOT master fill in flash but I am hoping to work a sound approach out for that too
09-27-2012, 08:10 AM   #10
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enoeske - great shots, you should probably write us a tutorial on Pentax flash
09-27-2012, 08:12 AM   #11
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I have not used my Metz 48 flash a lot with the K5 but the little I have used it, PTTL gave me overexposed shots and badly overexposed shots bouncing. I have pretty much given up on PTTL and have far better results in manual and doing + or - adjustments after a test shot or two. I don't use flash very much and most of my use is outdoors fill flash which I always use with manual settings.
09-27-2012, 08:18 AM   #12
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I've done a fair bit in PTTL with my k5 and flashes. I think the PTTL works great with the following limitations (based on a lot of use):

1 - Bounce flash has a minimum fire power that is too high for some combinations of aperture/iso and distance
2 - White areas can need negative FEC when bouncing (related to 1, but maybe also metering limitations?).
3 - Dirty contacts / bad seating can prevent PTTL working
4 - Very rarely the flash locks up and stops talking to the camera - best to take the batteries out and start again!

Last edited by johnc; 09-27-2012 at 09:11 AM.
09-27-2012, 08:42 AM   #13
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Try dropping the wide diffuser for bounce shots. Also, Auto ISO can be big trouble if the allowable range is too high. I would suggest limiting it to ISO 800.

I like X-mode for flash, with ISO 200, 400, or even 800 with a slow lens and/or dark scene.
09-27-2012, 09:06 AM   #14
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QuoteOriginally posted by audiobomber Quote
Try dropping the wide diffuser for bounce shots. Also, Auto ISO can be big trouble if the allowable range is too high. I would suggest limiting it to ISO 800.

I like X-mode for flash, with ISO 200, 400, or even 800 with a slow lens and/or dark scene.
Good suggestion re the diffuser (will help with the too high power problem). I sometimes grab the sto-fen but it is not always to hand!
09-27-2012, 03:02 PM   #15
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The key is the flash zoom setting

I can obtain predictable p-ttl exposure with my K-5 on firmware v1.12 and my AF-540FGZ flash
on camera in p-ttl bounce mode. But I must set the flash to manual zoom, otherwise exposure will vary with the zoom lens focal length, as the OP noticed.

I use the 18-55 kit lens, manual exposure mode 1/125, f/5.6, ISO 200, flash zoom set to 16mm, flash exposure compensation -1.3 set in camera.

QuoteOriginally posted by audiobomber Quote
Try dropping the wide diffuser for bounce shots.
This will work because it fixes the flash zoom setting at 13mm.

I suspect there's a bug in the p-ttl calculations that erroneously factor in the flash head zoom setting even in bounce mode.

Regards,
--Anders.
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