New Rebel Xti - Studio Settings?

rodneyk · Nov 20, 2007

I'm shooting people on paper backdrop, lighted with bounced 1000w quartz as main and two bounced 600w quartz as backfill with Canon Rebel Xti with f2.8 28-75

I'm having under exposure issues. I want that background WHITE.

What camera settings would suggest? Or what would fix this?

Sideburns · Nov 20, 2007

do you know how to use the thing?
If it's underexposed...expose more...lol.

longer shutter or higher ISO...
but if you want the background brighter but the subject is perfect...throw more ilght at the background perhaps. I'm not sure of your exact setup....but if it's a problem of it being too dark....then make it brigher.

Digital Matt · Nov 20, 2007

This kind of look is tough to get with continuous lighting. The background needs to have 2 to 4 stops more exposure than the subject, 2 being minimum. To maximize the efficiency of the lights, don't bounce the background lights, rather use them with no diffusion, direct on the background.

Big Mike · Nov 20, 2007

Welcome to the forum

Matt is right, you need more light on the background than on the subject, for it to appear white.

Also, it seems you are having trouble metering. The camera's meter will always try to turn the scene into a 'middle grey' or 18% grey tone. So if you have a lot of white, it will think it's too bright and give you settings that will underexpose from what you actually want.

The photographer needs to know this and compensate for it. There are several different methods of finding the 'correct' exposure. And you can use EC (exposure compensation) to adjust away from the camera's meter reading...or you can shoot in manual mode (which I would recommend). Your lighting is constant...so put the camera in manual and use test shots to find the exposure that you want...then just leave it there. Don't use the image on the LCD, but use the histogram to check your exposure.

Digital Matt · Nov 20, 2007

While I agree that using manual mode is the key, I disagree about checking the histogram. In this situation, the histogram (if you have exposed it correctly and the background is white) will show overexposure, and you'll have no way to judge the exposure on the model, which is really mission critical for skin tones and overall final look. In this case I think it's wise to learn how to meter, using a spot or center-weighted average metering system, and check the background and subject individually, in a kind of "zone sytem" fashion. This is what you would do were you shooting strobes, to make sure your ratio is correct.

nossie · Nov 20, 2007

Sounds like a job for Mr Peterson's Understanding Exposure. Rodney this a good investment of $16 in yourself.

Sideburns · Nov 20, 2007

Shoot manual. trial and error would be fine...

Big Mike · Nov 21, 2007

While I agree that using manual mode is the key, I disagree about checking the histogram. In this situation, the histogram (if you have exposed it correctly and the background is white) will show overexposure, and you'll have no way to judge the exposure on the model, which is really mission critical for skin tones and overall final look. In this case I think it's wise to learn how to meter, using a spot or center-weighted average metering system, and check the background and subject individually, in a kind of "zone sytem" fashion. This is what you would do were you shooting strobes, to make sure your ratio is correct.

Matt is correct. When shooting 'high key', the histogram will be skewed heavily to the right when the exposure is accurate...but if you understand that, it can still be useful.

mwvt9 · Dec 5, 2007

Big Mike said:
Matt is correct. When shooting 'high key', the histogram will be skewed heavily to the right when the exposure is accurate...but if you understand that, it can still be useful.

It is my understanding that there is no correct histogram. In other words, there is no ideal histogram for all exposures.

In this case as long you aren't losing any details to the right side of the histogram (in this case) you would be OK right? No matter how the picture is ultimately exposed the histogram is going to be skewed to the right (relative to the true midtones in the picture). So as long as the skewed details aren't getting cut off on the right side of the histogram you wouldn't be losing any detail. Is this correct?

I am new to all this so please bear with me.

Big Mike · Dec 5, 2007

Welcome to the forum.

The histogram is just a pictorial representation of the pixels in the image. The 'brightness' of is the horizontal axis and the number of pixels is the vertical axis. That's easy enough.

So if your high key image has a small subject in the middle of a large white background...then the vast majority of the pixels will be bright and will be piled up near the right side. However, you should still be able to see the 'blip' in the graph where the subject's pixels appear...and you should be able to get an idea of their exposure based on how close or they are to the larger part of the histogram.

That being said...there is no 'correct' exposure. Exposure is a choice that should be made by the photographer...and if you are not sure...then bracket.

JmPhotos · Dec 5, 2007

I'm sure it's not perfect, but it was my first try at high key. There has been no pp editing to this img. The settings are below. I had 2 35 watt white daylight balanced bulbs into white shoot through umbrellas in front of the subject and one 35 watt bulb, no difussion, behind the subject directed on the backdrop (white muslin). I would suggest two lights behind subject so the light is balance on both sides.

Shooting Mode Manual Exposure
Tv( Shutter Speed ) 1/8
Av( Aperture Value ) 5.6
Metering Mode Partial Metering
ISO Speed 200

Digital Matt · Dec 5, 2007

JmPhotos said:
Shooting Mode Manual Exposure
Tv( Shutter Speed ) 1/8
Av( Aperture Value ) 5.6
Metering Mode Partial Metering
ISO Speed 200

That is why I don't use continuous lighting.

JmPhotos · Dec 5, 2007

Why do you say this Digital Matt? I'm still learning. Any pointers would be helpful.

Digital Matt · Dec 6, 2007

JmPhotos said:
Why do you say this Digital Matt? I'm still learning. Any pointers would be helpful.

I can get the same look with a strobe light, and shoot at 1/250, and any aperture I choose. Continuous lighting is very limited because of the strength of the light source, which is usually very low in comparison to a strobe.

Btw, I can't hand hold a shot at 1/8, and I can also very rarely get a model to sit still enough to get a sharp shot either.

Big Mike · Dec 6, 2007

I completely agree with Matt.

I read something where a guy calculated the comparative strength of an average studio strobe to continuous lighting. It worked out that the strobe was equivalent to 100,000 watts...or something like that.

Of course, that's not really a fair comparison...but the point is that strobes are much more powerful, so they only need to put out light for a very short fraction of a second...which solves a lot of the problems that we have when shooting with continuous lighting.