Question about setting lights

[lviperz]

I'm a hobbist and I just got my first strobe kit off ebay. It was in my price range for playing.

Anyway, in my quest to find the right balance of lights and camera settings, I have a few questions. I don't have a light meter and know it would help, but what is meant by 160 watts per second? I assume it means the strobe is 160 watts at full power.

So if the strobe has a dial on it to lower the power down to 1/32 of full, does that mean the wattage is actuall being turned down? So at 1/2 power would make the strobe 80 w/s?

Also, the strobe have a model lamp. I see it can be used for posing and to help see what you are getting on the live view of the camera, but should I leave them on while I take the shot? Or what are the model lamps for?

And if you would like to see some of my first attempts at studio lighting, I have a post for C&C in the Portraits forum. Thanks.

[lviperz]

I forgot, I have another question. My camera manual says when using studio lighting to use full manual and set the shutter to the same or slower then the lights. So being that I have a 160 w/s light, I assume I set my shutter to 1/160 or slower. Or do I add all the lights together? 2 x 160 w/s plus 1 x 45 w/s = 365 w/s.

When using a 1/160 shutter speed, I have to set f11 for the apeture in order to get good exposure. So my question is, what do I do if I want to use a bigger apeture? Is it safe to shorten the shutter speed?

[ee50ok]

Removed as it appeared twice. Ooops!

[ee50ok]

Great questions:

I have to admit I've always just assumed that at half power you will get half the light output. But assumptions are a dangerous thing! Perhaps someone else can answer more fully.

You can adjust your camera shutter and apeture as you would normally (i.e balance one off against the other) until you reach the flash sync speed of the camera. Faster shutter speeds than this result in unevenly exposed images usually characterised by a darker area on one edge of the image.
I find I can control the depth of field by using both the light power output and the apeture and still stay within the flash sync speed quite satisfactorarily.

Good Luck.

[lviperz]

Thank you for the reply. I guess what I need to do is keep my shutter at the same speed as (or just slower then) the lights. In my case, since the lights are 160 w/s, then my shutter should be 1/125 to 1/160. My camera will do both. Then as I set my apeture for the dof I'm looking for, I lower the output of my lights to get the correct exposure.

Sounds simple enough. But I think I really need to get a light meter. Unless someone knows of a way to calculate the light output without a meter. I mean to calculate a good estimate. For example, say I have my main light set to 1/2 power and I want my fill light 2 stops down from the main. Can I calculate somehow that maybe 1/4 power would be close? Or do I simply have to take the shot and look?

[ee50ok]

I tend to take a test shot and look at the histogram on my camera. From that I can tell if the exposure is about right. I then make adustments (light output, shutter speed, apeture) and try again, and again, and again.....

[JohnC]

Watt Seconds is a measure of energy stored in the flash capacitors. It doesn't have anything to do with shutter speed. The duration of the flash itself is probably 1/500 second or faster.

Your camera shutter speed has to be set to the sync speed for your shutter (or slower). Nothing to do with the particular flash you are using. Look in the camera manual for the sync speed. You are generally safe to use 1/125 of a second. Use slower shutter speeds if you want to mix ambient light with the strobe. Changing the shutter speed on the camera will not have an effect on the flash exposure. If you set the shutter speed higher than the sync speed you will get a black band across one edge of your image. Lower shutter speeds, as noted above, will allow more of the existing light in the scene to affect the exposure. You might get some subject motion blurs, etc. But still no change to the flash exposure.

The power setting of the flash will determine your aperture. If you want to open up your lens you have to lower the power setting on your flash. Sometimes even at the lowest setting it is too bright. Then you need to use neutral density filters (on the lights or on the lens). You can move the light back, but that will change the quality of the light, making it harder (more shadows) and flattening out the overall scene (yes, it sounds contradictory).

[lviperz]

John, thank you. I think I understand. I looked at my manual and it says to set my shutter speed equal to or slower than the flash duration. As you said to do. So I looked up my lights and here is what I found.

Flashing Duration : 1/600 sec. @t=0.1; 1/1000 sec. @t=0.5

Now, what does the @t= part mean?

[JohnC]

Is this the camera manual or the flash manual that is telling you to set the shutter speed in relationship to the flash duration? Whichever, it is incorrect. You have to set your shutter speed equal to or slower than the flash sync speed for your camera's shutter. And that information should be in the camera manual.

The "t" reference is in regards to the curve of the flash power/duration and goes way beyond the discussion here. But you can see a post about it in the Paul Buff Forums at Paul C. Buff FORUM HOME :: View topic - Flash Duration Explained

[brice]

Originally Posted by lviperz

John, thank you. I think I understand. I looked at my manual and it says to set my shutter speed equal to or slower than the flash duration. As you said to do. So I looked up my lights and here is what I found.

Flashing Duration : 1/600 sec. @t=0.1; 1/1000 sec. @t=0.5

Now, what does the @t= part mean?

The fastest shutter speed you will need is 1/125 to 1/200 depending on personal preference.

The most important thing you need to know is the trigger voltage of the flash units. Make sure IT is not higher than your camera allows. Most consumer digital cameras are 6V.

[lviperz]

Originally Posted by JohnC

Is this the camera manual or the flash manual that is telling you to set the shutter speed in relationship to the flash duration? Whichever, it is incorrect. You have to set your shutter speed equal to or slower than the flash sync speed for your camera's shutter. And that information should be in the camera manual.

Ok, I'm confused. My manual, under the section for using the sync terminal says, set the shutter speed equal to or slower than the flash duration; refer to the flash unit's manual.

So that's why I posted the flash duration from the specs of my flash.

[lviperz]

Originally Posted by brice

The fastest shutter speed you will need is 1/125 to 1/200 depending on personal preference.

The most important thing you need to know is the trigger voltage of the flash units. Make sure IT is not higher than your camera allows. Most consumer digital cameras are 6V.

Yes, my camera manual says 400V or lower. The lights are 5V and I have already tested and they work.

[lviperz]

I just found the specs for the "flash-sync speed" for my camera. It actually says all shutter speeds. Can that be true? I did take some shots this weekend and I had my shutter on 1/2000 and I didn't get any black bands.

[highbarger]

The OP's sig states that he has a Minolta A2. According to the specs on DP Review, the flash syncs at all shutter speeds. I suppose this camera doesn't have a moving curtain shutter since it's a P&S. Is that correct?

Edit: You posted while I was searching...

[JohnC]

Ah! I thought the A2 might have been an SLR. Yes, a point and shoot might have an electronic shutter instead of mechanical. Then it could very well sync at all speeds.

That might even explain why they mention flash duration. I've never seen that before. But I typically work with cameras with mechanical shutters.

Thanks!

[lviperz]

Originally Posted by JohnC

Ah! I thought the A2 might have been an SLR. Yes, a point and shoot might have an electronic shutter instead of mechanical. Then it could very well sync at all speeds.

That might even explain why they mention flash duration. I've never seen that before. But I typically work with cameras with mechanical shutters.

Thanks!

Ah, so yet another reason to tell my wife why I need that new DSLR. Thanks everyone. I think I understand now. I have an orange and you all have apples. I need an apple.

[JohnC]

Being able to sync at all speeds is a "plus" for the camera you have now, especially if you try to use the flash outdoors and balance it with the sun.

[lviperz]

Originally Posted by JohnC

Being able to sync at all speeds is a "plus" for the camera you have now, especially if you try to use the flash outdoors and balance it with the sun.

Well this discussion really cleared things up for me. Thanks. And if anyone is interested, here is a link to another thread I started with some samples of what I shot this past weekend.

Need C&C on the studio lighting