[unkabin]

Thanks for the comparison shots. I'm surprised. I wonder how much ambient light was in the room--sunlight from windows, even diffused. I ask because since posting those pictures I took last night, I've been shooting some tests indoors with the flash today. With a bit more ambient light, the results aren't nearly as dark and, importantly, are much more consistent. But they only close in on proper exposure with a boost of +1 on the flash. Doesn't that turn my 540 flash into a GN of 27m?

I'm heading out this afternoon with my wife to a museum--not sure of their flash photog policies--but I'll go to a hotel lobby or somewhere if I have to for some out-and-about results.

[felix68]

I just did a meter reading of the same dining area, same conditions and I get 1sec at f5.6 and ISO 400 so I don't think that ambient affected my shots at all.
Just fired off a shot without flash at f5.6, 1/60th, ISO 400 and it came out completely black. This confirms that no ambient light contributed.

[unkabin]

Just a last addition to this thread. Back from the museum. High warehouse ceilings, so I used a rather large bounce card, and +.5 to +1 compensation. Here are a few representative shots, untouched by post processing. Some fill, some mainly flash. Not bad at all. A bit under in general, even with the bump in power, but all easily correctable in PP. As long as they remain reasonably consistent, I'm happy already, and I'll only get better with it. I probably shouldn't have jumped to a post after only testing in "test" circumstances. So often the real world is different. (even though this has made me think that the GN on this flash is optimistic)

[felix68]

Guide numbers are a tricky thing because there are a lot of variables involved. Most of the old workhorse flashes like my Vivitar 285HV have guide numbers based on ISO 100 with a 50mm lens at f1.0 and quoted as 120ft or about 40m. All of the new flashes, including the Metz with a guide number of 58, are using a longer lens and zoom head to claim higher quide numbers. Their specs, including the AF540 are almost the same 40m or 120ft at 50mm.
I am pretty sure that there is a limit to the amount of light that can be generated by any of these flashes due to the size of capacitors and the batteries being used. The real power of all of the top of the line units are pretty much on par.

[mattdm]

Guide numbers are a tricky thing because there are a lot of variables involved. Most of the old workhorse flashes like my Vivitar 285HV have guide numbers based on ISO 100 with a 50mm lens at f1.0 and quoted as 120ft or about 40m. All of the new flashes, including the Metz with a guide number of 58, are using a longer lens and zoom head to claim higher quide numbers. Their specs, including the AF540 are almost the same 40m or 120ft at 50mm.

From what I've seen, guide numbers are always quoted at f/1, and usually at ISO 100 (except for flashes built into a camera which uses a sensor with a higher base ISO — the specs for the K100D quote a guide number based on ISO 200, which works out to exactly the same as the K10D at ISO 100).

I am pretty sure that there is a limit to the amount of light that can be generated by any of these flashes due to the size of capacitors and the batteries being used. The real power of all of the top of the line units are pretty much on par.

From a practical sense, this is basically true, since they're all good enough for most purposes. But the actual value does vary. I've tried to provide a visualization of it here: Pentax P-TTL Flash Comparison: Flash Burst Profiles

[Wheatfield]

Just a last addition to this thread. Back from the museum. High warehouse ceilings, so I used a rather large bounce card, and +.5 to +1 compensation. Here are a few representative shots, untouched by post processing. Some fill, some mainly flash. Not bad at all. A bit under in general, even with the bump in power, but all easily correctable in PP. As long as they remain reasonably consistent, I'm happy already, and I'll only get better with it. I probably shouldn't have jumped to a post after only testing in "test" circumstances. So often the real world is different. (even though this has made me think that the GN on this flash is optimistic)

Personally, I think that is terrible performance. Your exposures are pretty much all over the place with nothing really exposed correctly.
When I sold cameras in the 80s, you could mount a flash to the camera (in programmed AE), and the flash and camera would talk to each other in such a way that the user didn't have to worry about settings, and they would conspire to give very accurate exposures.

Now, some 20 years later, we have to set our cameras manually and use auto flash to get accurate and consistent exposures, just like how we did it in the 70s.
Somehow we've devolved, and people are accepting of this.

[unkabin]

Wheatfield, I agree that it isn't great, but what is the alternative?

As an aside, I missed the 80s technology. I went straight from the 70s to this, and I was very surprised (negatively) by the performance of the flash.

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Last edited by unkabin; 01-25-2009 at 10:29 AM.

[felix68]

Personally, I think that is terrible performance. Your exposures are pretty much all over the place with nothing really exposed correctly.
When I sold cameras in the 80s, you could mount a flash to the camera (in programmed AE), and the flash and camera would talk to each other in such a way that the user didn't have to worry about settings, and they would conspire to give very accurate exposures.

Now, some 20 years later, we have to set our cameras manually and use auto flash to get accurate and consistent exposures, just like how we did it in the 70s.
Somehow we've devolved, and people are accepting of this.

My take is that the system overall has devolved. I still shoot a lot of film still and most have much more dynamic range than digital sensors. I think that the lack of DR is especially difficult for the manufacturers to design for in terms of flash. Most seem to just let the highlights blow out to get a more consistent exposure. Pentax seems to take a more conservative approach and not let the highlights get blown. I think that this also shows up as inconsistent results.
What I am wondering lately is if the 6MP sensor in the K100D is less subject to this issue because of the bigger photo sites. It really seems like my K100D is much more consistent than the K10D bodies.

[NeverSatisfied]

Man this thread (and the link to the other forum) really has me bummed out now, since I just bought a second 540 a couple months ago. I was going to try the Metz 58 but I didn't think it was worth the $100 more. Now I'm not so sure!
But besides the extra $$, my reasoning was that I didn't want to try to learn TWO different methods of operation for 2 different flash units (especially for wireless mode, etc.).
Now I -have- noticed the tendency to underexpose, but what baffles me is why in bounce flash, if you swivel and bounce for a vertical composition, it underexposes by at least ANOTHER whole stop, on top of its tendency to underexpose as it is. Using it in Auto mode does indeed seem to solve any underexposure problems.
However, I've tried a lot of variables, including the "Link AF Point and AE", changing from spot metering to matrix metering, using Program, or aperture-priority, or whatever- none of that seemed to make much difference, at least with the K20D. (Generally I shoot in manual mode.)
But I have found that, when using PTTL, adding +1 of flash compensation to the camera body does the trick, even pretty well with bounce flash, and THEN if I want to use the swivel-bounce for a vertical composition, I dial in +1 flash compensation on the flash itself (for a total of +2 in that particular instance).
If it wasn't for my wanting the wireless capability of the 540 (or similar), and maybe even more importantly the high-speed sync, I would've saved a helluva lot of money and just kept using my good old Sunpak 383's. In comparing those to the Pentax 540 in Auto mode, there is NO difference!

[Deni]

How difficult is to built an auto flash (similar to 285hv in power) that get's the apperture/iso/focal range from the camera and has af assist light?

Then market it for about $100 - 150. That's going to be a great flash imo.

[fearview]

This flash is about the biggest rip-off I've seen since the contractor who renovated my house left.

sorry for that too

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this post help me decide wheter i should pick up 540fgz or 58 AF1

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thanks

[unkabin]

But will a Metz behave differently? In p-ttl, isn't the flash doing what the camera is telling it to do?

[felix68]

But will a Metz behave differently? In p-ttl, isn't the flash doing what the camera is telling it to do?

I have not used the Metz but I wonder the same thing. Since the body is telling the flash when to cut light output, won't the Metz give the same results in P-TTL?
After another weekend of shooting, I am still loving my AF540 on the K100D. Getting some great shots of my 2 month old.



Please ignore if you don't like baby photos!