Softboxes...quick question...

Hey Folks,
Quicky question about softboxes... Basically I need to know if/how much light is "lost" using a softbox in regards to exposure. What's the rule of thumb here? Let's say I'm using a small 16"x16" softbox...how much do I need to adjust my f/stop compared with "direct" flash assuming the ws and power level are the same? How much does that change (if any) with a larger softbox such as a 24"x36"?

Not looking for specific mathematics here, just the quick rule of thumb.

Thanks!
Jim

The best rule of thumb is get a flash meter. A serious photographer should have a decent light meter anyway. This is not going to be the only sticky situation you will come across dealing with light.

jr_senator wrote in post #5520042
The best rule of thumb is get a flash meter. A serious photographer should have a decent light meter anyway. This is not going to be the only sticky situation you will come across dealing with light.

Yea, I actually have a flash meter and while I do use it, I actually find the histogram more helpful. This was just a question out of curiosity more than anything...I was wondering if it was like a polarizer where you can guestimate how much you need to compensate based on the size of the softbox.

For my double diffusion SBs, average light lost is about 1.5 stop, but every softbox is different.

The histogram does not give one an accurate exposure reading. There is no substitute for a decent light meter.

I'm sure that's probably true but for for most of what I do, I can tell more about the over-all lighting of any given scene from the histogram than I can from a light meter...a light meter only tells you the intensity of the light at the specific point where the light was measured.

In this day and age of digital and RAW, I don't usually shoot for "perfect exposure" anyways...I do sooooooo much work in Photoshop to begin with that if I have to push or pull the exposure a tad, it's no problem for me. As long as I'm not blowing highlights, the rest is a bit subjective. My primary concern is always more about composition and the look and feel of the lighting. My methods are often a bit unorthodox for others but they do work for me...and to me, that's what counts.

Peace,
Jim

Lotto wrote in post #5521054
For my double diffusion SBs, average light lost is about 1.5 stop, but every softbox is different.

Thank you...that was actually helpful! I do realize that the degree of loss is dependant on a number of other factors beyond size (such as internal grids, baffles, shape, etc) however if I may ask...what size softboxes do you use?


Thank you!
Peace,
Jim

I think the point about using a light meter is that it would take a few seconds to measure your strobe, with and without the softbox and find out how much light is lost. Guessing based on other people's equipment really won't get you very far, I have softboxes that cut 1 stop of light and others that cut 2.5/3 stops.

Walczak Photo wrote in post #5516480
Hey Folks,
Quicky question about softboxes... Basically I need to know if/how much light is "lost" using a softbox in regards to exposure. What's the rule of thumb here? Let's say I'm using a small 16"x16" softbox...how much do I need to adjust my f/stop compared with "direct" flash assuming the ws and power level are the same? How much does that change (if any) with a larger softbox such as a 24"x36"?

Not looking for specific mathematics here, just the quick rule of thumb.

Thanks!
Jim

Theres allot of variables in that. How much diffusion in the soft box distance from subject and how you are using it (which will help determine quality of light). Ya need a meter...Get the quality of light you desire FIRST them adjust the light level to the aperture you want/need.

Every soft box is different. You could meter without the box, and then meter with the box on. Simple as that.

Walczak Photo wrote in post #5522408
...I can tell more about the over-all lighting of any given scene from the histogram than I can from a light meter...

I think you may have a misunderstanding of how a histogram works, and just what it does. It is not a substute for a meter. As one of our members (bbbig) wrote earlier, "Histogram assumes that your scene is "normal", and since you'll never get such scene in real life, relying on histograms for your exposures will not give you desired photos." And, "For example, if you're shooting a subject in a big snow field, unless you calibrate your camera to a proper white balance first, then your image will come out underexposed. The histogram in that case, may show a pretty high singular peak in the middle region. However in "reality" the exposure should've been taken so that the histogram shows the high peak towards extreme right.

If you were "correcting" your exposures just based on what the histogram tells you, in above example instance, you will get severe under-exposure. Opposite is true when shooting against a dark background, etc.

This is why histogram really isn't very useful, other than to show the distribution of bright pixels once the photo is taken, properly exposed or not."

Please use the following link about histograms and you may well be surprised. http://www.sekonic.com …ghtmetersWorkTo​gether.pdf

Walczak Photo wrote in post #5522425
Thank you...that was actually helpful! I do realize that the degree of loss is dependant on a number of other factors beyond size (such as internal grids, baffles, shape, etc) however if I may ask...what size softboxes do you use?

Thank you!
Peace,
Jim

I use small one (22x16") with speedlights, and 48x36" with my ABs.

jr_senator...

I appreciate your attempt to "educate me" in regards to this subject and thus I will try not to take it too personally. However I must add that your argument also assumes that I'm a complete imbecile and don't know crap about photography or how to use my camera to begin with. I know to compensate for dark backgrounds, light backgrounds, snow, yadda, yadda, yadda, regardless of the histogram reading. Further, while you have been going on about how great and essential light meters are, you seem to forget that light meters can be fooled too. In either case, neither a light meter or a histogram replaces the photographer's eyes, brain and experience when it comes to evaluating any given lighting situation.

Please understand that while I'm sure my methods wouldn't work for you, they -do- work very well for me and again for me, that's the important thing. I have a flash meter and I do use it (occasionally). -I- get more out of reading the histogram. I could explain further, but I doubt you'd get it and you certainly wouldn't agree with it as from the tone of your post, you seem convinced that your way is the only way.

Regardless, I wasn't looking for a "rocket science" answer here and I thought I had made that fairly clear...all anyone had to say was essentially what Hermes said; "I have softboxes that cut 1 stop of light and others that cut 2.5/3 stops"...that's all I was looking for . I'm not sure why folks felt the need to make a bigger fuss out of it than that... (that was a rhetorical comment...no need to answer it).

Lotto and Hermes...thank you for your help.

Peace,
Jim

"I will try not to take it too personally. However I must add that your argument also assumes that I'm a complete imbecile and don't know crap about photography..."

Sorry if I offended you, it certainly was not my intent. I didn't mean to imply that you didn't know "crap" about photography, I'm sure you do. However, your question about a "rule of thumb" as to the amount of light loss using a softbox along with your preference of using a histogram for metering tells me you are lacking about the understanding of light and how to meter it.