Beginner with flash

I just received my flash lights and already encountered a few issues. It is my

first time using flash that I own and operate myself and I don't understand how

to obtain the desired exposure and depth of field. I would like to keep my work

at a large aperture (4.5 or 5.6) and keep shadows on my subject. However, the

profoto 7b seems to have very powerful light even set at minimum power, and

changing the shutter speed settings keeps the image too bright or the image is

half there and the other half is all black. I know I must sound like a complete

novice, but can anyone offer me a link to an online tutorial or any advice?

Thank you very much.<div></div>

Firstly, you need to understand that your exposure is controlled by the AMOUNT of light (from your flashes) and the size of your aperture - the shutter speed is almost irrelevant when using flash in a studio setting.

 

If you set too fast a shutter speed the shutter will not be fully open when you take the shot, as you've discovered - and if you set too slow a speed the flash exposure will be unaffected but your shot will be affected by whatever continuous lighting is also present.

 

Assuming that you're using your minium ISO setting, you can reduce the effective power of the flash by using neutral dentity gels in front of your lights or a neutral density filter in front of your lens.

 

For online tutorials, see the Lighting Themes archived in this forum

I had my ISO set at 400. Could that have been a contributing factor?

-- "and changing the shutter speed settings keeps the image too bright or the image is half there and the other half is all black."

 

If you're below sync-speed, changing the shutter-speed changes NOTHING (regarding the exposure with flashlight), since the flash itself is much faster. Above sync-speed, you get the half-bright half-black effect.

 

If you cannot reduce the poweroutput of the flash any more, you'll have to stop down (f/8 f/11) or lower ISO settings (if you use digital).

* had my ISO set at 400. Could that have been a contributing factor?*

 

No, it's not a contributing factor, it's the determining factor. 400 ISO increases sensitivity to light by a factor of 4 (2 stops) when compared to 100 ISO. In other words, if the correct exposure at 100 ISO is f/4, the correct exposure for 400 ISO would be f/8

Ditto the above responses - another way to reduce the light is to move the flash(s) further away from your subject.

thank you for your answers. one last question: what is usually the shutter speed for flash?

*what is usually the shutter speed for flash?*

 

Whatever it says in your camera manual. However, there's no need to set the highest possible speed, 1/60th will be fine.

thank you, I will give it a try soon and keep you posted.

IMHO, in this case it's better using bounce flash:

http://www.wikihow.com/Use-Bounce-Flash-to-Improve-Your-Photography

 

It should help avoiding washed out highlights and not so great looking shadows behind the subject.

Actually there are 2 things at play here (correctly pointed out above), if your shutter speed is too fast you will have dark bands in you photos as the shutter curtain is not fully open at time of exposure

 

the other thing is that shutter speed has got nothing to do with flash exposure! The flash emitted from the strobe is so short anyway that no shutter speed will make a diffrence. Remember this: shutter speed controls ambient light, aperture controls flash exposure

 

This means that if the images are too bright using your flash (assuming you don't want to balance with the ambient light, and it's amount is negligible, as it probably is in your case), you have to close your aperture, if it is too dark, open up the aperture (leave the flash output untouched)

 

Does that make sense to you? I can try to explain it better if you wish

Just wanted to thank you for your help! I tried again and this time it is working as I expected.

 

Hi Claude, I think it makes sense. But if you don't mind explaining in more detail... Thank you.

 

I'm also wondering what the experience people have with using light density filters to cut down the light. I wanted to create some photos with a wide aperture to have a nice blur in the background yet have the subject naturally lit.

Michelle,

 

Yes you could use Neutral Density (ND) filters (or a polarising filter), on your lens, to allow you to use a wider aperture. Using filters on the lights is usually not practical except on spot lights.

 

The ND filters are usually supplied as ND2, ND4, and ND8, they will reduce the light by one, two, and three stops respectively. A polariser (which you may already have) will reduce the light by about 1.5 stops.

 

If you are already using the lights at minimum power (maybe you bought too much power) and they are still too bright you can -

 

1) increase the distance of your light from your subject - double the distance = one quarter the light (check out 'inverse square law').

 

2) diffuse the light eg by using a softbox (some boxes additionally are supplied with an extra light reducing baffle).

 

or a combination of the above; also use slowest ISO available.

 

I think you have already understood about setting your shutter speed to or below your camera's sync speed.

 

Nick.

I agree with most of the points made by Nick, but feel that clarification may help.

 

Using neutral density gels on studio lights is entirely practicable. It's slightly more fiddly than using a ND filter over the lens, but has the advantage of not reducing image quality and allowing individual control of light output.

 

The relative size/distance of light from subject should be whatever produces the result you want. Never use distance as a means of controlling exposure, because moving the light closer or further will affect the quality of the light.

 

Very basic physics - the inverse square law does NOT apply (or at least in the linear terms expressed) to any source of light other than a point source. Studio lights are not point sources. I'm not going to get into yet another discussion about it, anyone who feels that I'm wrong should test it for themselves.

 

Diffusing the light doesn't reduce its quantity, it does however spread it around, which produces a similar effect - but, again, use a softbox because you want soft lighting, not to reduce the effective output. Lighting is all about quality, not quantity.

 

Hope this helps

Thank you for your responses. I also found a video tutorial that I found very helpful online regarding some of my questions:

 

http://www.studiolighting.net/digital-photography-one-on-one-e001-key-shifting-and-shutter-speed/