Using a Flash Diffuser

Discussion in 'Beyond the Basics' started by iskoos, Feb 15, 2012.

  1. iskoos

    iskoos TPF Noob!

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    Hi, I have a standard flash diffuser in my camera bag and I use it time to time to soften the light. I recently read an article about "How to Use Dome Diffuser..."

    The article was saying that using a diffuser would cause harsh shadows in certain settings and that not using it would prevent shadows (if I understood it right).
    I am not saying that the article was saying using a diffuser means shadow, and not using means not shadow. It is definitely not simple but I didn't seem to understand the main point of the article despite reading it a few times.


    The link to the article is below. I am hoping someone would help me see what I was missing. Basically I couldn't understand how not using a diffuser would be a way to prevent shadows on the wall when the light could easily bounce off the ceiling...


    How to Use Dome Diffuser to Eliminate Shadows and Harsh Light


     
  2. Rephargotohp

    Rephargotohp TPF Noob!

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    What the author is saying (but didn't really say) Is that you can put a dome diffuser on your flash, but you still have a very small light source, The smaller the light source, the "Harder the light on your subject and that will produce more shadow both on your subject and behind the subject also. There is less wrap around subject with a small light source. By instead taking the diffuser off and bouncing the light off the ceiling ( another form of diffusion) you are also creating a larger light source and also one that hits your subject from a different angle so even if it there was a shadow it would be placed lower below the subject and not behind them.

    Diffusion good, comes in many forms, size of light source important
     
  3. MReid

    MReid TPF Noob!

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    You can also diffuse your light source using ambient. If you get the mix right there should be little shadow...you do want some shadow to provide depth to your subject....but you do need to control it.
     
  4. iskoos

    iskoos TPF Noob!

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    So are you guys saying that the author took the picture (the one on the left with a distinct shadow behind the person) with a dome diffuser but the flash is pointed to the subject's face and then he took the dome off the flash and pointed the flash toward the ceiling and bounced the light off the ceiling and took the second picture?
     
  5. MReid

    MReid TPF Noob!

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    First picture the photo was taken in portrait mode with the flash on the side of the camera pointed straight at the subject.
    Second photo the flash was pointed up and bounced off the ceiling.
    He says he used the diffuser in both those first photos....the "diffuser" he is using is worthless to begin with....as said above it does not make the light source any larger or closer to the subject.
    In the second photo he increased the exposure to make it look harsh, while having a dark exposure on the second set....I would look for another source for info on diffusers...that guy is playing optical tricks and doesn't seem to know much about the subject.

    For me I point the flash straight up, increase iso and shoot wide open, I use a demb diffuser across the front of the flash.

    Essentially this adds light to the room as well as adds a bid of shadow to my subject from the bounce off the ceiling, if the ceiling is too high to get much bounce it still adds light to the room,....unwanted shadows disappear. Works for me.
     
    Last edited: Feb 15, 2012
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  6. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    That is the big mis-conception with most flash accessories and (I think) what the article was getting at.

    There are two ways to make light softer; make it larger and or reduce the distance from light to subject....that's it. Of course, there are other properties to light than just softness...but it's best to understand this principle.

    So simply putting some opaque material over/in front of you flash, won't make it any softer, unless it significantly increases the size...which that one doesn't.

    So if we are talking about light going directly from the flash to the subject, adding just about any of the popular flash accessories (Fong Dong, Omnibounce etc.) won't really improve the quality of light. But it's important to understand that in this scenario, these things are hurting your cause. The material eats up some of the light, so the flash has to work harder. They usually spread the light out in many directions, much of which is wasted, causing the flash to work harder than it needed to. The result is longer recycle times and shorter battery life.

    So if you're in the scenario of shooting the light directly from the flash to the subject, bare flash is often the best option, unless you can greatly increase the size of the light (softbox, umbrella etc.)
    The easiest/best way to increase the softness of the light from you flash, is to bounce it off of something large, like a wall or ceiling.

    Now, the key thing to recognize about these flash accessories, is that they spread or split the light. The let some/most of the light go straight out from the head, but they also send some in other directions. So, if you are going to bounce the flash off of the ceiling, most of the light is allowed to go up for that purpose, but some of it also goes directly to the subject, acting as fill, for the shadows that would be caused from the bounced light. Or, the light goes out in many directions, and if there are surfaces for that light to bounce off of, it (hopefully) comes back to the subject nice and soft...and from multiple directions, wrapping the subject in light.

    So the key thing to know and understand, is that in the right scenario, where you have good surfaces to bounce the light, these flash accessories can be great. But if you're not in that scenario, know when to take it off the flash and just use it bare.
     
    Last edited: Feb 16, 2012
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  7. iskoos

    iskoos TPF Noob!

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    Thank you all. I have no objection to what's said here. I understand the diffuser is no gurantee solution to prevent shadows. It is just that when I read the above article, it sounded like the omni diffuser being used was responsible for the shadows and removing the diffuser helped. In fact (if I understood correctly) he shot the first picture with the diffuser pointed to the subject then he removed the diffuser and pointed the flash to the ceiling for the second picture. This is to me not a fair comparison. That was the part that got me confused. Obviously this article won't be my guide when using diffuser...
     
  8. KmH

    KmH In memoriam Supporting Member

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    Bouncing flash off a ceiling often makes shadows where you don't want them, like in people's eye sockets.

    Bouncing flash can introduce other problems too:
    • the light has to travel farther. The Inverse Square law shows that if distance is doubled, light is reduced 4 times (a square function). Double the distance again and light is reduced 16 times.
    • additional light is lost because few bounce surfaces are 100% reflective
    • the light can pick up a color cast from the surface the light is bounced off of.
    Shadows are not necessarily a bad thing in a photo. Shadows are used to add depth and definition, but the photographer definately wants a great deal of control over where and how sharp edged any shadows are.
     
  9. Christie Photo

    Christie Photo No longer a newbie, moving up!

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    ALL very well put, Keith. It's as if you read my mind. Thanks.

    -Pete
     
  10. DiskoJoe

    DiskoJoe Been spending a lot of time on here!

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    Thanks for this explanation. I (also) just got a my first external flash and some diffusers and gels to go with it and this is really helpful.
     

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