help using flash indoors

[Greg Beetham]

Yep ADI can be very good with direct flash, especially with an OEM (D) lens and a OEM (D) flash, but not infallible, I have seen odd occasions using my A100 / KM5D and KM (D) lenses with either the KM 3600HS (D) or the Sony F56 [read KM 5600HS (D) ], in conjunction with honeycombe metering the exposure system become involved and overrule the ADI system preventing overexposure...I can draw no other conclusion...it doesn't happen often, but nevertheless it appears it can happen.
That aside, there is also a distinct possibility that the flash used may not distinguish between APS-C format and FF format, as far as I know there is only one or two Sony flashes that can do that, the F42 and the F58. If the flash can only read lens focal length and relate that to FF, then at 18mm wide angle the flash GN may be as low as 14 or 16, not enough power for ISO 200 at f8 for any more than a couple of meters.
That's why I recomended to try manual zooming the flash head.....in a similar situation/composition that is.
Greg

[Dusty]

Exposures are metered for an averaged 18% gray. That large white tablecloth in so much of the frame is causing your problems. Try the same scene with a dark blue tablecloth and see what yo get.

Dusty

the EXIF shows that the OP use ADI -no 18% gray principals here...

Not quite. The ADI is only setting the flash to meter that 18% gray at the focus distance. The correct exposure will nearly always be computed for an 18% reflectivity of the subjects. The problem becomes one of when your scene doesn't average 18% reflectivity. Shoot a black object, the camera will they to make it gray. Same goes for a white scene. I always used manual flash for weddings because the Bride's dress will always look dingy if you let the flash or camera set the exposure.

Dusty

[pakodominguez]

the EXIF shows that the OP use ADI -no 18% gray principals here...

Not quite. The ADI is only setting the flash to meter that 18% gray at the focus distance. The correct exposure will nearly always be computed for an 18% reflectivity of the subjects. The problem becomes one of when your scene doesn't average 18% reflectivity. Shoot a black object, the camera will they to make it gray. Same goes for a white scene. I always used manual flash for weddings because the Bride's dress will always look dingy if you let the flash or camera set the exposure.

Dusty

ADI is based on distance, not in reflectivity. Using ADI will give you a black black, not a gray black -well, if the camera/flash work as the manual said...

[stevecim]

In other hand, there is no reason for the flash to underexpose that bad. The Exif doesn't show any exposure compensation (the exposure compensation on my A700 change "by itself", regarding on the day, and i have to keep checking all the time)

Is this the first time you have this kind of issue with this flash? is this the first time you use this flash?

Regards

First time I've used the flash, I don't remember ever having problems like this with a sunpak 4000F (power zoom flash) on a Minolta 600si body.

tried gain this weekend , mixed bag sort of results, tried bouncing of the ceiling , the house had a low white ceiling, tried manual zoom, dialing up some flash comp.
One thing , I could not get the flash into manual mode when it was attached to the body. I don't know if this is normal.

[stevecim]

Y
That aside, there is also a distinct possibility that the flash used may not distinguish between APS-C format and FF format, as far as I know there is only one or two Sony flashes that can do that, the F42 and the F58. If the flash can only read lens focal length and relate that to FF, then at 18mm wide angle the flash GN may be as low as 14 or 16, not enough power for ISO 200 at f8 for any more than a couple of meters.
That's why I recomended to try manual zooming the flash head.....in a similar situation/composition that is.
Greg

Yes, I just checked the flash and lens and when I set the lens to 28mm the flash zooms to 28mm , when the lens is at 50mm the flash is zoomed to 50mm, I guess this means the flash is always going to under expose? does the 1.5 crop also affect distance readings?

[pakodominguez]

First time I've used the flash, I don't remember ever having problems like this with a sunpak 4000F (power zoom flash) on a Minolta 600si body.

tried gain this weekend , mixed bag sort of results, tried bouncing of the ceiling , the house had a low white ceiling, tried manual zoom, dialing up some flash comp.
One thing , I could not get the flash into manual mode when it was attached to the body. I don't know if this is normal.

I guess if you was working on A or P modes the flash won't go to manual mode.
I think I'll send that flash back to the place you bought it and buy the Metz Mecablitz 36 AF-4 (http://www.adorama.com/MZ36AF4S.html) for less money, or the Metz 48 AF-1 (https://www.adorama.com/MZ48AF1S.html) if you need wireless, more power and firmware updates.

[pakodominguez]

Y
That aside, there is also a distinct possibility that the flash used may not distinguish between APS-C format and FF format, as far as I know there is only one or two Sony flashes that can do that, the F42 and the F58. If the flash can only read lens focal length and relate that to FF, then at 18mm wide angle the flash GN may be as low as 14 or 16, not enough power for ISO 200 at f8 for any more than a couple of meters.
That's why I recomended to try manual zooming the flash head.....in a similar situation/composition that is.
Greg

Yes, I just checked the flash and lens and when I set the lens to 28mm the flash zooms to 28mm , when the lens is at 50mm the flash is zoomed to 50mm, I guess this means the flash is always going to under expose? does the 1.5 crop also affect distance readings?

The 1.5 crop factor doesn't affect exposure, only how wide the area lighted will be. I think the new 42AM and 58AM are the only flashes that convert the flash zoom on APS cameras, to the 35mm equivalent. DK run a flash test a couple of years ago and the Sigma (I don't recall if he used your model or not) underexposed by default.

[Greg Beetham]

Yes, I just checked the flash and lens and when I set the lens to 28mm the flash zooms to 28mm , when the lens is at 50mm the flash is zoomed to 50mm, I guess this means the flash is always going to under expose? does the 1.5 crop also affect distance readings?

All it means is that if the flash only adjusts the zoom setting for FF (regardless of whether it's on an APS-C or FF) it's wasting power by a factor of about 1.4 when it's on a APS-C camera, (according to a site on flash I was reading the other day), but if the subject is in range and the other settings are OK there is no reason why it can't take excellent photos.
Direct flash is great for candids, and magic for backlit light balencing, but it has one large drawback, and that is the subjects at different distances problem. Light falls away by the square of the distance, so if a subject in the shot is twice as far away as a foreground subject (that is exposed correctly) the background subject receives four times less light...it's just one of those base laws, nothing we can do about it except try and work with it.
What I try and do in poor ambient lighting is, limit my candid composures to one or two people in the shot so the background doesn't matter all that much.
But if a group shot is necessary then try and have the subjects at a similar distance from the camera, within a few feet of each other (furthermost-nearest), that is usually quite ok, there is also more latitude in the furthermost-nearest distance the more you increase the distance between you and the subjects.
With that reasonably wide angle shot along the table, attempting that one with direct flash (no subject re-arranging) would only possibly succeed with manually zooming the flash, carefully aimed down the middle of the table at the head of the end subject with just the right amount of flash zoom...like I said before you would have to experiment with a couple of zoom settings to see which one worked the best...or least worse...
btw it does actually work, because I've done it myself.
Greg