450D Flash sync and general hot shoe mount problem

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Crazy Dino

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I have a 450D as the name suggest however im fed up of always having to stick the camera in manual when using the flash due to the cameras wonderful ability of not being able to calculate a shutter speed when in aperture priority to compensate for the flash. Anyway, I was flicking through the custom functions[, and discovered I can activate a function that set the shutter speed to 1/200 when using a flash. Should I do this, or are there drawbacks?

Lastly the silver hot shoe mount on the top of my cam has come loose, which is a problem when shooting portrait as it isnt making connection to the pins. Advice, or should I just superglue the mount to its original position?
 
Two-second job to tighten it, just pop the wee plate off the hotshoe and you'll see the screws holding it in place. Tighten them up - job done :thumbs:
 
Crazy Dino said:
I have a 450D as the name suggest however im fed up of always having to stick the camera in manual when using the flash due to the cameras wonderful ability of not being able to calculate a shutter speed when in aperture priority to compensate for the flash. Anyway, I was flicking through the custom functions[, and discovered I can activate a function that set the shutter speed to 1/200 when using a flash. Should I do this, or are there drawbacks?

Lastly the silver hot shoe mount on the top of my cam has come loose, which is a problem when shooting portrait as it isnt making connection to the pins. Advice, or should I just superglue the mount to its original position?
Click to expand...

That statement doesn't actually make sense Dino. Shutter speed has no effect on the flash exposure.

In Av, the camera will try to set an exposure that is both correct for the ambient light (by adjusting the shutter speed) balanced with correct exposure for the flash (by adjusting the power output). It might not get it right, but there could be various reasons for that - pretty much anything except the shutter speed!

By enabling that custom function you are locking the shutter speed, so the camera has no scope to adjust for the ambient light. It cannot have any effect on the flash exposure.
 
HoppyUK said:
That statement doesn't actually make sense Dino. Shutter speed has no effect on the flash exposure.

In Av, the camera will try to set an exposure that is both correct for the ambient light (by adjusting the shutter speed) balanced with correct exposure for the flash (by adjusting the power output). It might not get it right, but there could be various reasons for that - pretty much anything except the shutter speed!

By enabling that custom function you are locking the shutter speed, so the camera has no scope to adjust for the ambient light. It cannot have any effect on the flash exposure.
Click to expand...

Basically in apertrue priority with the flash on, the camera calculates the shutter speed for if the flash was not there, even with a flash on it will give you 2 second shutter speeds in dim light for example.
 
Crazy Dino said:
Basically in apertrue priority with the flash on, the camera calculates the shutter speed for if the flash was not there, even with a flash on it will give you 2 second shutter speeds in dim light for example.
Click to expand...

Ah right, I misread you, apologies.

Actually, the camera does attempt to moderate both the ambient exposure and the flash, by comparing the dynamic range of the ambient exposure with that of the pre-flash.

How well it works is a matter of opinion but the functionality is there in the algorithms. See this link - it's very detailed, but good http://photonotes.org/articles/eos-flash/

However, it's easy to control things yourself, by moderating the flash power output on the gun with +/- compensation, and by moderating the shutter speed with +/- compensation on the camera. Most people like to work in Av for this.
 
Remember also that if your camera chooses a shutter speed over 1/200 then your flash will be firing in focal plane mode (not sure if Canon call it that, but thats what Nikon call it), which will reduce the amount of power from the flash - seriously reduce it...
 
I may be teaching grandmothers to suck eggs here, but for normal flashguns and focal plane shutters, there's a maximum shutter speed that can be used. It used to be 1/60th, but in modern cameras it's usually 1/250th. This is because at faster than 1/250th, the shutter travels across the film/sensor as a slit, so the flash exposure - which is measured in micro-seconds will only hit part of the film/sensor. Below 1/250th, the second shutter curtain travels across after the first curtain has travelled fully, so the whole of the film/sensor is exposed. If you preset the shutter speed to 1/200th, then the ambient light will not necessarily be exposed correctly. Remember - aperture controls the flash and shutter controls the ambient when mixing ambient with flash. On the 450D, I think you can set either forced 1/60th or 1/200th for flash sync.
 
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