Cobra 450af what will happen


webba

Link Posted 19/08/2010 - 19:50
I have k10d I have been told that the cobra 450af will not work on this camera as its ttl not p-ttl ,what I was wondering is what would happen if I tried to use it has anybody actualy tried?

Pentaxophile

Link Posted 19/08/2010 - 20:20
Yes I have this flash unit. Just put it in manual mode and adjust your aperture till you're getting correct exposures.

These settings work for me - indoor, bounced flash off ceiling: ISO 200, shutter speed 1/125, aperture f5.6.

"M" selected on flash.
[link=https://500px.com/will_brealey/[/link]
Last Edited by Pentaxophile on 19/08/2010 - 20:22

webba

Link Posted 26/08/2010 - 19:31
thanks m8 I tried it and it works .It also seems to be working ok in P and green whats that all about then?

Pentaxophile

Link Posted 26/08/2010 - 22:33
Dunno but if it works it works! I used manual mode as I assumed it wouldn't communicate with the camera.
[link=https://500px.com/will_brealey/[/link]

Dangermouse

Link Posted 26/08/2010 - 23:08
Try putting it in P mode and setting your camera to P - if I do that with a Pentax AF240Z and a K-m I get program flash with the camera detecting the flash and setting its aperture/shutter speed to suit. Varying the ISO changes the aperture.
Matt

Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.

webba

Link Posted 31/08/2010 - 14:35
After futher testing it seems fine in P mode it even AF asists in pitch darkness.

I have even gone on to try an old miranda pentax ttl flash with simular results except no AF light so its rubbish in low light situations which is sort of when I need a flash but its great in manual mode.

So my question is why does it say everyware that you canot use ttl flash's with the K10 or later.

am I missing somthing here or do I have a magic k10

Pentaxophile

Link Posted 31/08/2010 - 14:49
Are you really putting it through its paces? Does it compensate when you change the iso or aperture?

The af assist light is very futuristic, eh?
[link=https://500px.com/will_brealey/[/link]

webba

Link Posted 31/08/2010 - 15:39
Pentaxophile wrote:
Are you really putting it through its paces? Does it compensate when you change the iso or aperture?

The af assist light is very futuristic, eh?

I am using it in p and auto iso (range set between 100-400) so the camera decides all that.

I dont really do much flash photography but I have been taking test shots in varying conditions and the results seem faily consistant at least as consistant as the built in flash.

I am really impressed with the af assist I hate the onboard one and the nasty noise it makes also the time it takes to lock focus and take the shot

Dangermouse

Link Posted 04/09/2010 - 15:08
Be a bit careful before you go clipping any old flash on - check the trigger voltage first. You can do this with a multimeter set to measure DC volts, just turn the flash on, let it charge, then touch the positive probe to the centre stud and the negative to the side contact on the hotshoe foot.

I mention this as I've just found a couple of harmless-looking tiny flashes running from 2 AAs which have trigger voltages of over 200V! Needless to say neither will be going anywhere near my K-m. It appears that Pentax units are safe, although you should check. You can pick up a multimeter for 5 and it'll be handy for diagnosing faults in all sorts of things.

I suspect you're using the same mode as my K-m and AF240Z do - it seems as though Pentax included support for the old Program flash mode (from the pre-TTL era on things like the P30T) in their DSLRs. The camera takes account of the flash, sets the right aperture according to the ISO you set, and then sets a shutter speed according to its metering.

The modern digital bodies will even work with the early AF160 - I tried mine last night while bored and found that with camera in M mode with the shutter set to 1/180 and aperture set according to the table on the back of the unit I got both a "flash ready" indicator light and perfect exposures while using the Auto modes on the flash. I doubt I'll use this combination much (bought it as a pocket flash for my ME Super) but it was still nice to see technology from about thirty years apart working happily together!
Matt

Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.

Pentaxophile

Link Posted 04/09/2010 - 15:13
There is a list somewhere of the safe flashes and their voltages... needless to say I checked this first before trying the Cobra.

Quote:
I suspect you're using the same mode as my K-m and AF240Z do - it seems as though Pentax included support for the old Program flash mode (from the pre-TTL era on things like the P30T) in their DSLRs. The camera takes account of the flash, sets the right aperture according to the ISO you set, and then sets a shutter speed according to its metering.

This is very interesting to know!
[link=https://500px.com/will_brealey/[/link]

Dangermouse

Link Posted 04/09/2010 - 15:40
I'm basing that assumption on the fact that if I set both camera and flash to P, then change the ISO on the camera, the aperture changes to match (when compared to the ISO table on the flash). Shutter speed seems to stay far lower than the sync speed of 1/180 but I've never had any problems with blurring.

What I don't know is whether the flash's light sensor plays any role. I know with the original Auto flashes (AF160, AF200S) it did, as you were effectively handing over metering to the flashgun which would give the correct light output for a good exposure providing that you had set the camera as it expected.

I may have to put a finger over the sensor and see what effect it has!

Edit, tried that, it does seem to make a difference. The shot taken with a finger over the sensor was overexposed, which would suggest that it does vary the output.
Matt

Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.
Last Edited by Dangermouse on 04/09/2010 - 15:50

Anvh

Link Posted 04/09/2010 - 16:36
Pentaxophile wrote:
There is a list somewhere of the safe flashes and their voltages... needless to say I checked this first before trying the Cobra.

Here's the list http://www.botzilla.com/photo/strobeVolts.html
Stefan


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