[PeteyJ]

For the life of me I can't find an answer to this anywhere on the internet or in the manual, and a search of these forums turns up no results that are relevant to this either.

When I have the thing mounted to my camera, the LCD says that it has a range of about 12 feet at f/4 and ISO 100. This changes a little bit depending on the focal length I'm using on my lens, but it's always indicated to be somewhere around 12 feet.

Now the guide number of the Metz 48 is 48 meters, which is about 158 feet as ISO 100. I recently learned how to do Manual flash because of all the complaints I heard about P-TTL and exposure, so I know that to calculate range in full manual, you do the following equations.

Guide number/distance = f/stop

So lets say my subject is 12 feet away. Using that equation (158/12 = 13.17) means I should use an f/stop between f/11 and f/16. As mentioned above, the LCD indicates that this distance of 12 feet is the maximum effective distance when I have f/4 set. This is a huge discrepancy between the two.

So what's going on with my flash? I upgraded to the latest firmware for the flash the other day, and never noticed this problem until then, but at the same time, I never knew anything about manual flash until right before I upgraded, so I don't know if the firmware screwed it up or not.

Any help would be much appreciated

[adwb]

hm thought it was just me, I have the same thing and have to up the iso to 400 to get the distance that the table in the hand book predicts for iso 100 or maybe I just dont understand any of it.
alistair

[PeteyJ]

Well good, I'm not the only one. Hopefully someone here can help us.

[LinXitoW]

look at what it says in the manual: guide number at ISO 100, Zoom 105mm: 48

[PeteyJ]

look at what it says in the manual: guide number at ISO 100, Zoom 105mm: 48

I did look at the manual. For one, the 48 is meters not feet so the guide number is actually about 158 and, as I mentioned, when changing focal lengths/zoom of the flash, the range indicated on the LCD changes only marginally.

So once again, with a guide number of 158 feet at ISO 100, and an aperture of f/4 and a focal length of 105mm, I should have an affective range of 39.5 feet, not around 12 feet, give or take a foot or two as indicated on the flash's LCD.

[LinXitoW]

I was talking about zooming the reflector.

[StarDust]

Flash guide numbers always tend to be exaggerated, not that they're wrong, just that they always give the best possible numbers.
This means that when zooming the flash to the longest focal length and at maximum power you will get a guide number of 48, meaning good exposure at 48 meters.
This is normal with flash makers and after learning that I learned the capabilities of different flashes.
So, when you zoom out, the light will spread more meaning that less light is focused at longer distances and will then be more poorly lit.
Different makers and flashes have different focal lengths so if you plan to buy a secondary flash it might be good to look up those specs like focal length for the flash when buying it.

I just recently got my Metz 48 and am very happy with the strength. I would say it's a normal strength flash with good TTL and tilt+swivel capability. If you want much stronger, I would recommend Vivitar flashes or Sunpaks. Have in mind though that they are fully manual.

[PeteyJ]

I was talking about zooming the reflector.

Yes I know. The zooming reflector on the 48 changes automatically to match the focal length of the lens (usually).

Flash guide numbers always tend to be exaggerated, not that they're wrong, just that they always give the best possible numbers.
This means that when zooming the flash to the longest focal length and at maximum power you will get a guide number of 48, meaning good exposure at 48 meters.
This is normal with flash makers and after learning that I learned the capabilities of different flashes.
So, when you zoom out, the light will spread more meaning that less light is focused at longer distances and will then be more poorly lit.
Different makers and flashes have different focal lengths so if you plan to buy a secondary flash it might be good to look up those specs like focal length for the flash when buying it.

I just recently got my Metz 48 and am very happy with the strength. I would say it's a normal strength flash with good TTL and tilt+swivel capability. If you want much stronger, I would recommend Vivitar flashes or Sunpaks. Have in mind though that they are fully manual.

Oh I'm quite happy with the 48 too, except just for this LCD thing. When I do everything in full manual mode, the Guide Number/distance = f/stop calculation is usually pretty accurate, so the strength isn't much of a problem for me.

I even just tested it in P-TTL mode. I stood about 30 feet away from a subject. 158/30 = about 5.6 so i set to f/5.6 and shot at ISO 100 (reflector zoom was 105mm as well). Exposure was spot on, but the LCD indicated the range of the flash would have been only 17 feet

[Ratmagiclady]

I'm pretty bad with numbers, (I don't even try to calculate mathematically, I just picture things and think in 'stops,') but needless to say, that doesn't sound right at all. Basically, I don't know why the readout tells you that and I'm going to wag a cane and wonder whatever happened to the good old calculator dial.

Thought: is the flash properly seated on the shoe? Clean contacts? Maybe it's not quite talking to the camera.

[PeteyJ]

Thought: is the flash properly seated on the shoe? Clean contacts? Maybe it's not quite talking to the camera.

Yep, the socks and shoes are clean and everything fits perfectly.

The only thing I could think of is maybe it's giving me a distance somewhere in between the minimum and maximum effective ranges for that f/stop in P-TTL mode, which would make a little bit of sense I guess.

[Ratmagiclady]

Yep, the socks and shoes are clean and everything fits perfectly.

The only thing I could think of is maybe it's giving me a distance somewhere in between the minimum and maximum effective ranges for that f/stop in P-TTL mode, which would make a little bit of sense I guess.

I intend to get hold of a P-TTL flash soon enough, myself (This was *not* a point in favor of going Pentax to begin with, but, all things considered, here we are.)

I do wonder if perhaps, since P-ttl is pre-flash based, if the display you are seeing is actually somehow related to *ambient* light, then back-calculating that to a corresponding range? ... and doesn't even 'count' until said preflash fires? Metz units aren't expressly-designed for Pentax, after all, as nice as they are. Just adapted. But I speculate wildly. Don't think I have a clue.

[Russell-Evans]

This is what I get, setting manual zoom on the flash, at ISO 100 and f4 on my Metz 48 AF-1, P-TTL or M:

39ft / 12m @ 105mm -> GN 48
35ft / 10m @ 85mm -> GN 40
31ft / 9.6m @ 70mm -> GN 38.4
28ft / 8.7m @ 50mm -> GN 34.8
23ft / 7.2m @ 35mm -> GN 28.8
21ft / 6.5m @ 28mm -> GN 26
19ft / 6.2m @ 24mm -> GN 24.8
17ft / 5.3m @ 18mm -> GN 21.2

Even with +3 FEC at 105mm in P-TTL mode, I get 13ft / 1.8m.

Thank you
Russell

[PeteyJ]

I'm an idiot. I loaned someone my camera for a few days, and never realized they left the exposure compensation set to +2 stops. Today I was doing some actual shooting and realized this when all my stuff was washed out. As soon as everything was set to normal, I put the flash on and bingo, the display on the flash was accurate.

[Ratmagiclady]

I'm an idiot. I loaned someone my camera for a few days, and never realized they left the exposure compensation set to +2 stops. Today I was doing some actual shooting and realized this when all my stuff was washed out. As soon as everything was set to normal, I put the flash on and bingo, the display on the flash was accurate.

This is why I like dials I can touch.

[Russell-Evans]

This is why I like dials I can touch.

Well it does show the FEV on the display if you care to look. I probably am like most people and still push on the door when there is a sign that says pull.



Thank you
Russell