Re: speedlights

[shane1980]

I'm new to flash and have two questions,

1. Is there a reason why flash sync is 250th rather then 60 th? Whats the difference ??

2. When people refer to flash power is it flash compensation or flash sync speed ??

I'm a newbie go easy lol

 

[Finste]

I'm new to flash and have two questions,

1. Is there a reason why flash sync is 250th rather then 60 th? Whats the difference ??

2. When people refer to flash power is it flash compensation or flash sync speed ??

I'm a newbie go easy lol

1. 1/250 is usually a maximum sync speed. You can sync at any speed at or slower than this. Your 1/60 would also be fine for sync. The maximum sync speed is the fastest time where the sensor is fully exposed.

2. Neither. Flash power for studio lights is usually rated in Watts. e.g. 600w or 300w. Flashguns, e.g. Canon 580Ex, however are usually rated in guide numbers. Its usually available on the flashgun somewhere. Just how guide numbers are related to watts is something I'll leave for more experienced folk.

Steve

 

[specialman]

I'm new to flash and have two questions,

1. Is there a reason why flash sync is 250th rather then 60 th? Whats the difference ??

It has to do with the amount of time the shutter requires to open and close, the shutter being a focal plane shutter (i.e. a pair of moving curtains). Any faster than 1/250th and there is the risk that the the whole sensor wouldn't be fully exposed by the flash burst, hence why shooting at high shutter speeds you get a black band across the frame - this is the part of the sensor that was covered by the shutter curtain when he flash popped. Modern flashgun have a built-in hack to get round this, usually referred to as High-Speed Sync, where the flash pulses so as the gap in the shutter curtains moves across the sensor, the whole of the sensor receives an equal amount of light. This pulsing reduces effective range of the light, so you'll hear many people talking about HSS reducing overall power. It's more about the flash being spread out over the series of pulses and not in one blast - each pulse is a fraction of the overall power so won't light as much of the scene.

1/60th is well below the point where the whole sensor can't be exposed by the single pop of a flash burst. The upper curtain hasn't started travelling down before the lower curtain has reached the bottom of the sensor.

When people refer to flash power is it flash compensation or flash sync speed ??

On speedlights, the GN rating is usually based on a set ISO (like 100) and then metered at full power to see how far the light goes.... or something like that

In terms of speed light power, 1/1 is obviously full power, 1/2 is half of full power, 1/4 is a quarter, 1/8 and eights and so on. 1/64th or 1/128th are usually present on the high-end flashes. These low flash powers have very short flash durations so come in useful for freezing action, such as when doing water droplet shots.

Of course, those figures above only show when using the flash in manual.

In TTL mode you'll see values like +1 and -2 displayed on the flash. It's a case of understanding what '0' on the flash means to that particular exposure and then knowing that if you dial it down by -1 it'll give you a result that you require. The '-' and '+' relate to flash compensation.

You can tell I use manual a lot more than TTL

 

[shane1980]

Specialman,


So when it's in ttl mode and if I adjust the flash exposure either on flash or in canera this is basically adjusting the power is that correct obviously in manual it be as u said...

 

[specialman]

I can't quite remember how flash exposure comp works on Nikon.

Just had a play and in AV, dial in compensation on the camera and you're controlling the ambient. If you adjust the flash then you increase the flash power.

 

[shane1980]

So if I leave the flash in ttl bl mode and turn the camera to manual is this the only way I can achieve shutter speeds up to 250th obviously bar fp mode.

 

[specialman]

So if I leave the flash in ttl bl mode and turn the camera to manual is this the only way I can achieve shutter speeds up to 250th obviously bar fp mode.

Any flash mode with work up to 1/250th. It's above this that FP mode kicks in, although it's a seamless transition - the camera won't alert you to the fact because if you go to, say, 1/500th, the flash will still just work, but with a reduced contribution to the exposure in terms of distance.

Keeping it in manual and at 1/250th guarantees that you don't exceed flash sync speed - I tend to shoot in manual (on the camera) and then either use manual flash settings when I have time to work on flash ratios and what not, or I just stick it in TTL mode and the flash just does the heavy lifting; if I need a bit more flash I just increase it on the flash, keeping the exposure on the camera as-is, only altering that via the aperture. I usually start at somewhere like 1/250th against an ISO that will give me a reasonable background exposure (with the aperture at something like f/5.6) so the background is slightly underexposed. Then the flash just fills in the blanks.

By the way, TTL BL is a balanced mode where the camera always tries to create a more balanced look between flash and ambient.

Taken from photo.net:

TTL: Through-the-Lens flash metering
TTL-BL: Balanced fill flash between flash and ambient light
TTL-FP: Focal Plane flash: permits flash photography with a shutter speed faster than the camera sync speed, which is typically 1/250 sec or 1/200 sec on Nikon DSLRs. In the * TTL-FP mode: the flash uses a sequence of pulse flashes to get round the sync speed limitation so that it can sync with as fast as 1/8000 sec but at reduced flash power. The higher the shutter speed, the greater the flash power reduction.
A: Auto, instead of using TTL flash with a flash meter inside the camera to measure the amount of flash, use a flash metering sensor built inside the flash to control the flash level. Among iTTL flashes, this feature is only available on the SB-800 and SB-900
M: manual, control the flash level manually at full, 1/2, 1/4, 1/8…typically at 1/3-stop increments.

 

[shane1980]

Thanks for the info your a legend