studio lighting - depth of field

You should never move a light to change its effective power because doing so changes the quality of the light.
If you want to reduce the effective power just fit a neutral density gel over the light. Personally I find that 0.9 (3 stops) is the most useful. If that isn't enough, double it.
A workaround of course is to fit a neutral density filter to the camera lens, although that can make focussing difficult as well as possibly reducing image quality.

has more to do with the camera's aperture and the distance of your subject from the background and to the camera. wide aperture, with subject far from the background and camera near subject will throw the background out of focus and give a narrow depth of field. ppl commonly run into this problem because they don't have a large enough studio and or big enough background to move it back far enough from the subject. if you using a cheap zoom lense they usually don't open that wide, so i'd recommend a fast prime lens. naturally once you open the lens you'll need to dial down the strobe power.

you get soft light by having a large source relative to subject size.

One way to keep your lights close and soft is to use less light. With a softbox and a monolight combo if you still have too much light even if workign at a very low ISO number you can put scrims or extra diffusion between the softbox face and the subject to knock down the light. Adding diffusion can ahowever change the color characteristics of the light (usually warming it up). For awhile Chimera or another company sold a product caleld Screems which were wire scrims that attached to the Softbox speedring and those are useful for knocking light intensity down as well (they do get hot however.). These show up on eBay from time to time.

If you need to knock the strobe power down below the minimum setting, try clipping some neutral-density gel to the inner diffuser in the softbox. I find it to work well in situations where my strobes are just too bright, even at minimum setting.

Or, it has been suggested using just the modeling lights, but those aren't bright enough for me.

<Chas>

I second Charles' suggestion as that what I currently do. I use the small binder clips from an office supply store to clip multiple neutral density filters to the inside of my soft boxes. Works wonders without affecting the color of the light. You can buy them in sheets at your local camera supply store. Very affordable way to solve your problem. I found that it made sense to take an Avery label and mark the exposure factor in one of the corners of the filter since the printing on the labels is usually so dang small. Good luck.

thank you for all your replies & help

gary, you say that one should never move the light to change its effective power... just to make sure i understand. if im in a situation where i want a HARD LIGHT, do i then move the light back? or do i fit in a smaller light source? (small softbox, barndoor, honeycomb etc.) im confused when to move the light back and forward and when not to...

It's all about *relative* size of the light to subject as has already been said, so a big light far away is small relative to the subject, just like a small light up close. For hard light a small softbox is better than a big softbox assuming they're both at the same distance....but for hard light you probably don't want a softbox at all. Honeycombs help control the direction of light better as do barndoors.

Depth of field is primarily to do with your camera aperture, the problem you are having is a large aperture to give you shallow depth of field lets more light in - so if your strobe power stayed constant the scene would get brighter as you opened up the aperture to make the depth of field shallower...take a few shots and observe. Your methodology seems to be you adjust your aperture until you get the brightness you want - then seem surprised you now have a larger depth of field than you wanted (but this is to be expected, because you are reducing your aperture - even tho the f number gets bigger - which lets less light in but also increases depth of field).

The key here really is establishing a depth of field you'd like in your portrait first by setting your camera aperture, then if this is overexposing reducing the power output from your strobes using the methods listed above, but leave your camera alone! Yes moving the lights further away reduces their power which will stop your overexposure but makes them now seem smaller compared to where they were, thus changing the *quality* of light from soft to harder and more directional.

I hope that makes sense, but you should certainly be able to light what you want with the lights,...is the room you shoot in white? If you can't turn their power down and you don't have room to move the lights back you could fire them away from the subject at the wall(s)/ceiling....you then turn the wall into a big light source to bounce light onto the subject and you'll lose some of the power in the process if you are struggling to reduce the power in your strobes (which should be first priority). I'm sure someone else will help out if I've made any mistakes in trying to summarise things. Good luck - John

Studio flashes are sometimes simply too strong for small apertures...
That is why I also have some relatively weak flashes in my arsenal.
You can read a review about one very cheap and useful flash I found on B&H.

What sort of lights are you working with? While the neutral density filter will reduce your light intensity, I've never run in to trouble with dialing down the power on my Speedotron lights, or my White Lightnings. The 2403cx pack I have can send from 2400 w/s all the way down to 50 w/s through a single light. If I attach a second light pointing away from the set to 'bleed' off some power, it's down to 25 w/s, which is a very small kiss of light. Most monolights offer a good range of adjustment as well. The modifiers you are using also affect the amount of light-softboxes tend to be pretty efficient, while a gridded beauty dish is less so.
You can also use black cloth to control bounced light, which will help reduce the amount of light you have bouncing around.