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Umbrellas and f-stop

  
 
Luis Cunha
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p.1 #1 · p.1 #1 · Umbrellas and f-stop


Hi, I'm thinking of buying 45" umbrellas and using it with the Westcott FJ200 (200 watts/s) flash. Please someone help me to understand the following.

On the Westcott website it says translucent umbrellas subtract 1 f-stop of light. I'd like to know what it's like in terms of f-stops with respect to:

1. White umbrella to reflect the light. How much will you lose?

2. Silver umbrella to reflect light. Lose or win? How much?
Does Standard or Deep models make a difference in light intensity? Or just in the way of focusing the light?

3. Regarding the diffuser fabrics, for the white and silver umbrellas, it says on the website that they are 1 f-stop fabrics (the same used in the translucent ones?). Should this value be added to what is lost (if lost?) when the light is reflected on a white or silver umbrella?

4. Does the silver umbrella actually increase the available light or is it a myth and only reflects the same light as the white one, but with slightly different characteristics?

Thanks so much for your help.



Apr 10, 2022 at 09:06 AM
CharleyL
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p.1 #2 · p.1 #2 · Umbrellas and f-stop


I think you are getting a bit "hung up" on precise measurements and F-Stops. You are over thinking this. It's best to test these modifiers in your own location, be it studio or other, to see the results. With experimenting you will learn what soft and hard lighting means, and how to work with it. Softer light means less sharp transition between bright and shadow. The softer the light source the more gradual the transition and more even the light on the model.

Some times you want this and sometimes you don't, Shiny jewelry looks flat in soft light, but sparkles in hard direct light. Skin looks best when evenly lit without shadow lines. The larger the size of the light source, the softer the light is, but it also will not be as bright as the smaller light source. The light is getting spread out over a larger surface. White umbrellas do reflect light some, but their translucent material makes them work better as diffusers where the light is passed through them to toward the model rather than reflected off of the inside surface.

I have one 45" translucent white umbrella, and true, the light passing through it will be about 1 F-stop less than not using it with the same light source, but the light quality for photography will be much softer and better, due to the size increase from the light source to the umbrella size, if your light source is spreading wide enough to light the entire umbrella. Using a Godox SK300 light (the smallest that I have), and using this size white translucent umbrella and light source in my white wall/ceiling studio I get very satisfactory soft light results when lighting a model about 5' from the umbrella.

When you add a diffuser to a light source, if your light source can illuminate the entire diffuser (umbrella) the diffuser then becomes your light source for measuring spacing between light source and model (inverse square law). A white translucent umbrella spreads light in all directions. If your studio is all white, some of the light will be reflecting off of all of the white surfaces and back on the model too. The light is spread well before it reaches the model, giving very soft, even light. But the light hitting the white walls and ceiling of my studio is also reflecting in all directions and making this umbrella light source effectively even larger, so very, very soft light reaches the model.

A silver umbrella is a reflector, not a diffuser. The distance from your light source into and then back out of the silver umbrella adds to the distance between your light source and model and allows spreading of the light based on this increased distance. With increased distance between light and model the Inverse Square Law causes less light to reach the model. Without a diffuser, it will be harder and more focused light too. There will be very little light reflecting off the ceiling and walls, even if they are white.

If you add a diffuser to the silver umbrella you will then get a better diffused and more even light from it on your model at slightly less brightness (1 F-Stop) because of the diffusion of this material. The result will be somewhere between the translucent and silver umbrella in use. Again, if the light source spreads sufficient to light the entire diffuser, your light source will be the diffuser surface, so 45" diameter, but it will be more directed toward the model with much less reflected off the white walls and ceiling, so a bit harder light than you get when using the white translucent umbrella in this white studio at the same light level settings. Putting math numbers on all of this gives me a headache. I just learned from testing what works well for me. Knowing what the inverse square law means is far better than trying to apply it mathematically to every situation. Again, a little experimenting with the light and subject spacing will give you what you need to know without the need to mathematically solve each situation.

I have a pair of 32" white translucent umbrellas, a pair of 32" silver reflector umbrellas, and a pair of
32" gold reflector umbrellas. I've had them for probably 25 years, because I bought them when I first became interested in portrait and studio photography, but had no studio. I tried them and they worked, but I never cared for the gold umbrellas because I didn't like the color change result that they gave me. I prefer 56-6200 K, so bright white. Silver works, but I like using the white translucent as diffusers.

Then one day a photographer friend said that 32" was too small and that I needed much larger. Well, about that time I was building my studio in my home with an 8' ceiling, which limited me to something less in diameter. I wanted 72", but wasn't successful at finding 72" easily at a reasonable price, so I went with the 54". On experimenting with it, I found that there is an improvement over the 32", but not as much as I had expected. For portrait work, the 32" are just fine in my white studio. I have pairs of many sizes of soft boxes that usually get used for my portraits in the studio now, but there isn't anything at all wrong with using umbrellas.

You need to learn by practice and testing what result each soft box, umbrella, diffuser, light source, etc. will do for you, so you can decide which will do the best job for you and your way of shooting. Don't get hung up on the math.

I learn by doing. I understand the math, but don't see the need for exact math measurements and math calculations. Learn how each works for you through some experimenting and test shots. Never mind trying to solve photography via math. Understand the basics through experimenting and enjoy the process. What is available, like umbrellas, soft boxes, speedlites, studio strobes, etc. all work, but learning what each does better, so you can choose the right one for the situation, is what makes great pictures and you a great photographer.

Charley




Apr 10, 2022 at 11:23 AM
story_teller
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p.1 #3 · p.1 #3 · Umbrellas and f-stop


Some things you might want to consider. First, is buying the book Light, Science and Magic. The second thing is to buy or borrow a light meter and finally buy or borrow a combination of umbrellas - shoot thru, silver reflector and white reflectors. Then start measuring the light at a consistent power and distance (from the light source). What you'll find is that the amount of light falling on the subject varies based on the shape of the umbrella, the reflective material used, where the light is placed on the umbrella shaft, etc. There are no industry standards for the materials used in or the shape of the umbrellas. Some "white" umbrellas are more cream colored, some have a bit of reflective material, etc. White in not always white and silver is not always silver.

In general, silver reflects more, white diffuses (scatters) the light more. The more scattered, the less concentration of light on the subject. I'm sure others will join in with additional information.



Apr 10, 2022 at 11:30 AM
Luis Cunha
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p.1 #4 · p.1 #4 · Umbrellas and f-stop



Thank you very much, CharleyL and story-teller for your answers.
I'm sorry but I forgot to mention that I have different types of work to do with the umbrellas:

Real Estate - for when I can't reflect the light on ceilings (or walls) or even when I can reflect the light but I want the light a little less harsh, macro and still lifes in the studio, very occasionally some portraits and also reproduction of drawings and small paintings on paper.

I'll choose the umbrellas for now, which are the most accessible, and possibly later on other types of modifiers suitable for each case. Knowing what I lose and what I gain, in terms of light intensity, in the case of umbrellas is a great help.

I am aware of the Inverse-square law.
I will not use the golden umbrella.
Definitely translucent for interiors.
White and silver for other uses.
And yes, practice will fine-tune usage and modifier choice for each case. I also intend to buy a light meter later.

To simplify the initial question, without complex math .-) I think it goes something like this (at least approximately):

1. Translucent umbrella, cuts 1 stop.
2. White inner umbrella, cut nothing.
2A. White inner umbrella, + diffuser fabric (softbox type), cuts 1 stop.
3. Silver inner umbrella, 1 stop gain?
3A. Silver inner umbrella, + diffuser fabric (softbox type), cuts 1 stop.
4. Standard or Deep models, only focuses more or less the same amount of light. No gain or loss.

Correct me if I'm very wrong, but roughly speaking, it should be something like this.

Cheers .-)



Apr 10, 2022 at 12:05 PM
story_teller
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p.1 #5 · p.1 #5 · Umbrellas and f-stop


I would agree on bypassing the gold umbrellas. If you need a bit more warmth, use CTO (Color Temperature Orange) gels. They come in 1/4, 1/2 and full strength (and yes they will cut the light a bit as well).

Your rough assumptions about the different umbrella configurations are in the right direction, but I still hesitate to quantify the amounts due to all the variability.

Best of luck with your new venture.



Apr 12, 2022 at 07:49 AM
 


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CharleyL
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p.1 #6 · p.1 #6 · Umbrellas and f-stop


I agree with @story_teller, but feel that you should be buying and using a light meter as soon as possible.

You will learn far more, and faster when you can see the different results with the light meter.
Only by measuring the results will you know what each modifier is doing or not doing for you, and it will simplify your desire to take photos in different environments at the same light levels. It doesn't need to be one of the high priced ones with all the bells and whistles. Just a good reliable basic one that can measure ambient light as well as flash. My Sekonic L308 works well for me at about $220. Only if you use filters frequently or do video will a light meter with more features be of significant help to you.

Charley



Apr 12, 2022 at 11:08 AM
Luis Cunha
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p.1 #7 · p.1 #7 · Umbrellas and f-stop


Some minor corrections, as I found out from Westcott:
Translucent umbrella; 1 f-stop loss.
White umbrella; 1.5 f-stop loss.
Silver umbrella; 1 stop loss.
The other values I had written are correct.
The surrounding environment always has some influence.
They added that fabrics do not increase light output.

Hope this is for the benefit of the community here .-)
Thanks for your tips and help.



Apr 14, 2022 at 01:42 PM
Peter Figen
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p.1 #8 · p.1 #8 · Umbrellas and f-stop


Instead of fixating on the numbers like you have, concentrate on using equipment and modifiers that give the result you're looking for, then if you need more light you can add higher power or multiple flash units to do the job. Light meters for digital are most often a waste of time as so many of the cameras themselves are not calibrated to neutral gray. If you can shoot your real estate images (or any) tethered to a laptop, that will be more accurate and precise than any meter, sorta like seeing an 8x10 really instant Polaroid. You'll also learn rapidly how to correlate the LCD screen to what you see on your computer. I mean, I carry one with me but never use it anymore.


Apr 14, 2022 at 05:15 PM
story_teller
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p.1 #9 · p.1 #9 · Umbrellas and f-stop


Luis Cunha wrote:
Some minor corrections, as I found out from Westcott:
Translucent umbrella; 1 f-stop loss.
White umbrella; 1.5 f-stop loss.
Silver umbrella; 1 stop loss.
The other values I had written are correct.
The surrounding environment always has some influence.
They added that fabrics do not increase light output.

Hope this is for the benefit of the community here .-)
Thanks for your tips and help.


If it's true that fabrics do not increase light output, why does the silver reflector only have 1 stop of loss and the white umbrella have 1.5 stops of loss? Think about it.

If I line one umbrella's interior with black fabric and another with white, they will have the same amount of light loss?? Please look up the term "negative fill".



Apr 15, 2022 at 10:49 AM
Luis Cunha
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p.1 #10 · p.1 #10 · Umbrellas and f-stop


I also think they were wrong, but that's what they told me.


Apr 15, 2022 at 12:38 PM







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