Manual mode on a SB-80DX

Hi all, just seeing if anyone can explain to me what the fractions

mean when shooting in 'M' mode on my SB-80DX.

It starts at 1/1 and moves up to 1/2, 1/4, 1/8, 1/16, 1/32, 1/64,

1/128.

Can anyone tell me what these fractions mean and how I can pick one

to use at a given situation.

I am using the SB-80DX on my Fujifilm S3 Pro which is also in 'M'

mode.

 

Cheers

 

Benjamin

Benjamin,

 

The M mode means manual unlike automatic. The 1/1 means full power, 1/2 means half

power, 1/4 quarter power and so on. You should have stayed awake in math class.

Anyways with a hand held meter you will be able get your f stop with any of these settings.

Since you have a digital camera you can also just pick on setting and take a picture and

see how much light it is putting out. These settings help you fine tune and have complete

control over your flash.

 

Michael Mowery

"Anyways with a hand held meter you will be able get your f stop with any of these settings."

 

How does one determine the f-stop with a hand held meter?

Hold it near your subject, point the meter's dome to your camera, and trigger your flash. The meter will register the amount of light that reaches the subject and calculate the f-stop you have to use in conjunction with your camera's flash sync shutter speed.

 

The different power ratings on your flash correspond to stops on your lens. Suppose you set your flash to 1/4 and your meter says to use f8. If you want more depth of field, you can increase flash power to 1/2 or 1/1, and use f11 or f16, respectively. If you want less depth of field, you can decrease flash power to 1/8 or 1/16, and use f5.6 or f4.

"how I can pick one to use at a given situation."

 

F-stop and distance are the keys here. F-stop and distance determines how much flash power you will need.

 

The closer you are to your subject the less power you will need on your flash, 1/16, 1/32, 1/64 etc...If you are shooting with wide open f-stops, 1.8, 2.8, etc...you will need less flash power.

 

The farther away you are from your subject requires more flash power, and if you are shooting with your f-stops closed down, f16, f22, etc...

 

I would experiment, that is really the way to learn manual flash.

 

I very rarely ever use 1/1 power, especially because I like to shoot wide open and up close and I find that with direct flash I usually am using 1/8 to 1/32 on my manual flash. Everything factors in on this, ambient light, the effects I am looking for, ISO. I really do not like flash and always like the ambient light in balance with the flash, so in situations with ambient light I slow the shutter, open the lense wide and cut the power on the flash as much as I can.

If I may, here's how flashes work in Manual:

 

The fractions indicated on any flash have nothing to do with increasing or decreasing

POWER. The flash output is always the same: Full.

 

When you decrease the settings on the flash in Manual, you are shortening the duration of

the full power flash. The smaller the fraction, the shorter the flash duration and the less

light falls on the subject in terms of time, not amount.

 

Roughly speaking, each fraction corresponds to a decreasing f stop of light: 1/2= 1 stop

difference. 1/4 = 2 stops, 1/8 = 4 stops 1/16 = 8 stops.

 

The 4 things that control proper exposure are all interlinked using this math. ISO indicates

the amount of light needed to strike the film or sensor. Lens aperture controls the amount

allowed to strike it (think of it like a faucet: open=more, closed down= less). Shutter

speed controls how long the light hits it, (think of it like a window curtain: open it for a

long time and light hits it longer, i.e., slow shutter speed like 1/10th of a second. Open

the curtain and close it quickly, and light hits the film or sensor very briefly ... (as in

1/1000th of a second) ... the 4th controller is optional: flash. It adds light to what's

already there. The controller of flash is duration. Longer duration places more light on the

subject, shorter duration places less. Because of this, flash can be better understood if you

think of it like the way shutter speeds work.

 

If you arrive at a proper exposure with a meter, then aperture, shutter speed and flash

duration are now all interlinked to one another. Change one, and you have to change one

of the others to keep the proper exposure. F stop measurement is how you keep track of

that.

"When you decrease the settings on the flash in Manual, you are shortening the duration of the full power flash."

 

Ahhh!

It needs clarifications since Marc confused the issue saying:

 

"The fractions indicated on any flash have nothing to do with increasing or decreasing POWER. ... When you decrease the settings on the flash in Manual, you are shortening the duration of the full power flash. The smaller the fraction, the shorter the flash duration and the less light falls on the subject in terms of time, not amount."

 

Actually Marc means BRIGHTNESS, and not power.

In Marc statement replace the word "power", with the word "brightness" and all will be OK.

 

The max power (or rather more accurate is energy expressed in Watt Seconds - or in Joules) of a flash is determined by flash internal capacitor size (in Farads), and by internal working voltage (Volts DC).

 

When you set flash in Manual at 1/2 on flash POWER ratio scale (really should be Energy Ratio scale), then the flash will only release half of the POWER (or energy - to be precise). And similarly, when you set at 1/16, the flash will only release 1/16 of POWER.

 

In all cases the brightness of the flash blast is at its full capacity, to provide approprite light color temterature. Since the brigtness is always FULL, then to release less POWER (or energy) the flash reduces duration of the light.

 

Good luck!

This is basic physics. Flash duration does change the "power" output of the flash. Power is the area under the curve when you plot intensity vs. time. To a first order approximation the intensity does not change at different power settings. (The rise time of the flash intensity output is not instantaneous, and for very low power, short duration flashes, the intensity does not reach its peak before being quenched.)

 

In any case, when using shoe mount flashes, which have very short durations compared to studio flashes, the duration of even a full powered flash is much shorter than the camera's fastest sync shutter speed.

You guys are confusing the issue with facts ; -)

 

Yes "light intensity" rather than "light power" is correct, and needs to be a constant or the

temp of the light would alter.

 

Still, the way to think about it in simplistic terms most humans can understand, is that the

strobe light hitting the subject ... is hitting for shorter or longer amounts of time. That's

the key part to understand.

 

Why that part? Because, flash duration is what allows you to drag the shutter on the

camera in low light. As Ben said, most on-camera flashes have a maximum duration way

faster than the sync shutter speed of the camera. So, in dark conditions full duration flash

will usually freeze subjects even if they're moving and you are using a slower shutter

speed.

Looks like everybody is right, we just use different nomenclature.

 

However, Bruce is wrong saying:

 

"for very low power, short duration flashes, the intensity does not reach its peak before being quenched."

 

Such a flash would have not guarantee of constant light color temperature, and would be useless for color photography.

 

Flash out put of modern units that are on the market, always provides (within acceptable tolerances) the same color temperature, if set at Full, 1/2/m, 1.16, of the Power, or whatever design allows. In each of these instances the flash light brightness reaches the peak value to achieve rated color temperature.

Geez, everything has to be a freakin debate! Wow you guys are so smart! Marc Williams, thank you for your simple explanation, I have been shooting for 6 years and I learned something from your statement. Yes, I am no rocket Scientist so simplcity wins every time for me. Thank you.

But it's a nice debate that leads to clarity rather than personal insults ; -)

 

Automatic TTL flashes tend to keep you in the dark, pardon the pun. If you work with studio

strobes, which requite all manual calculations to balance multiple lights, you pick up on how

this stuff works a little quicker.

Correction of above: ... "require" all manual calculations ....

"However, Bruce is wrong saying:

 

"for very low power, short duration flashes, the intensity does not reach its peak before being quenched."

 

Such a flash would have not guarantee of constant light color temperature, and would be useless for color photography."

 

I've read technical papers, with plots of intensity vs. time, and at very short durations the flash does not reach full output and there are color shifts. I'll bet that there are color shifts between different power levels (even in the middle of their power ranges) and even shot to shot variations at the same power level for most shoe mount flashes. They may not be very visible, but they are measureable. It's one of the reason why some commercial studio photographers are very fussy about what brand of lights they use (and why lots of them use Profoto).