Have a, sometimes random, problem with OCF

[eric-holmes]

Sometimes my OCF is so hot it will completely destroy a picture. I will include a couple of examples. But I cannot figure out why is sometimes does this and sometimes doesn't. On these photos I was using TTL and my commander mode on the D90 set to "--". I don't understand how a shutter speed of 1/200 and 1/250 makes this much difference.

Camera Maker: NIKON CORPORATION
Camera Model: NIKON D90
Image Date: 2010:09:28 18:45:02
Focal Length: 42mm (35mm equivalent: 63mm)
Aperture: f/7.1
Exposure Time: 0.0040 s (1/250)
ISO equiv: 200
Exposure Bias: none
Metering Mode: Spot
Exposure: Manual
Exposure Mode: Manual
White Balance: Auto
Flash Fired: Yes (Manual, return light not detected)
Color Space: sRGB

Camera Maker: NIKON CORPORATION
Camera Model: NIKON D90
Image Date: 2010:09:28 18:45:31
Focal Length: 42mm (35mm equivalent: 63mm)
Aperture: f/7.1
Exposure Time: 0.0050 s (1/200)
ISO equiv: 200
Exposure Bias: none
Metering Mode: Spot
Exposure: Manual
Exposure Mode: Manual
White Balance: Auto
Flash Fired: Yes (Manual, return light not detected)
Color Space: sRGB

 

[edouble]

First off you were shooting in manual flash mode not ttl. Take another look at your camera's settings. Commander mode should be ttl not --

 

[Big Mike]

If you were using TTL, you have to realize that the flash exposure is dependent on an automatic reading of the the light from a pre-flash...and as such, it can sometimes be hard to predict or sometimes it's just wonky.

For example, maybe in one shot, the bright reflection from the helmet, is within the metering are, and so influences the exposure (probably causing underexposure). But if it's outside the metering area, it might not influence the exposure, and you might get over exposure.

I haven't used TTL with OCF, but I'd assume that the hit to miss ratio is higher than when using the flash on-camera.

This is one reason why people like using manual flash....because it's consistent. And by the way, changing the shutter speed will have no affect on the flash exposure (unless you exceed the max sync speed).

 

[kundalini]

Sorry, I can't see your photos but I wanted to comment on this.....

Commander mode should be ttl not --

It depends. If the intent is to fire OCF and have the buitl-in flash to contribute to the scene, the yes it should be set to "TTL" or "M". However, if the intent is just to trigger an OCF, then "--" is the correct setting.


I noticed there was only 29 seconds between shots. Had the flash fully recharged, were the batteries at low capacity? Again, I can't see the photos, so I don't know which one is over/under exposed.