Which Flash?


AlexJamesNicol

Link Posted 07/09/2011 - 11:37
Hi
Im using a K5 with a 18 to 250 lens and need a flash unit, ive been looking at both the AF-360FGZ and AF-540 FGZ. I take a lot of watersport photos at the full 250 and the speed is also very important. So which one do people recommend? Im a student so cost is important.

MattMatic

Link Posted 07/09/2011 - 11:40
Watersport photos at 250mm with a hand held flashgun?

What distance and ambient light conditions are we talking about? (ie ISO + shutter speed + aperture)

(Because I'm not sure if even the AF-540-FGZ can generate that much light!)
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 07/09/2011 - 11:41

moonstomp

Link Posted 07/09/2011 - 13:26
Hi Alex,

How far are you from your subjects? This will determine how effective any flash unit will be.

The AF540FGZ is a more powerful unit than the 360 version, but with a higher price tag to match though.

I'm no expert but here's my understanding of flash range. The maximum GN (Guide Number) of the AF540 is 54, while for the AF360 it's 36. Divide this number by the aperture value that you are using to get the effective range of the flash in metres.

So if you're using the AF540 and an aperture of F6, then your range is 9 metres (or 54/6). If you're any further from the subject than that then the flash will be of no benefit.

Hope that helps?

Further info here: link

Regards,

George.

K-5, Sigma 17-70 DC, FA 50 1.7, DA 50-200 & Metz 58AF-1.

MattMatic

Link Posted 07/09/2011 - 14:38
@George:
The effective GN also depends on the ISO setting I presume your quoted values are for ISO100.

The higher the ISO, the further the effective flash distance.

So, if you have a GN of 54, with an aperture of f/5.6 at ISO 100 that's 9.6m
But, at ISO200 you can calculate the same as ISO100 at f/4 = 13.5m
Going to ISO400, calculate as ISO100 at f/2.8 = 19.3m


Probably best for the OP to specify the conditions and then we can give more of an idea...

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

moonstomp

Link Posted 07/09/2011 - 16:07
MattMatic wrote:
@George:
The effective GN also depends on the ISO setting I presume your quoted values are for ISO100.

The higher the ISO, the further the effective flash distance.

So, if you have a GN of 54, with an aperture of f/5.6 at ISO 100 that's 9.6m
But, at ISO200 you can calculate the same as ISO100 at f/4 = 13.5m
Going to ISO400, calculate as ISO100 at f/2.8 = 19.3m


Probably best for the OP to specify the conditions and then we can give more of an idea...

Matt

Thanks for the clarification Matt,

Yes I should have noted that the GN's related to an ISO of 100. I've no experience of using flash at distances greater than 5 or 6 metres myself. It's hard to comment on the OP's chances of success without further detail on the distances he has to contend with.

Cheers,

George.
K-5, Sigma 17-70 DC, FA 50 1.7, DA 50-200 & Metz 58AF-1.
Last Edited by moonstomp on 07/09/2011 - 16:07

thoughton

Link Posted 07/09/2011 - 17:51
As said above, distance is everything. If they are a long way away you are probably out of luck, although if you have a lot of spare cash lying around you might be interested in this surfing photoshoot: link. 200-400mm lens and 8 (!) flashes. He gets some great pics though!
Tim
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
Flickr Fluidr PPG Street Portfolio site
Feel free to edit any of my posted photos! If I post a photo for critique, I want brutal honesty. If you don't like it, please say so and tell me why!

MattMatic

Link Posted 07/09/2011 - 18:01
Wow! And that was still 8 strobes at ISO2000 (yes two-thousand).
Cool
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

rparmar

Link Posted 07/09/2011 - 22:16
I would get the Metz 58 AF-2 depending on cost. I bought the previous model used for a decent price.
Listen to my albums free on BandCamp. Or visit my main website for links to photography, etc.

MattMatic

Link Posted 07/09/2011 - 22:25
...I wouldn't bother getting anything unless it'll do the job required

More info definitely required
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

xbow

Link Posted 08/09/2011 - 21:42
I don't use a flash that much so I got the Metz 44 AF-1 which I'm very pleased with.

Vic.
K5, LightRoom 5
Sigma 8-16 Pentax DA 16-45 Pentax DA 55-300 Pentax 18-55WR Tamron 90 Di Macro Metz 44 AF-1
Last Edited by xbow on 08/09/2011 - 21:44
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