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Flash Zoom

iroseirose Member
edited January 2011 in flash & lighting
Just finished reading On-camera Flash Techniques for Wedding & Portrait Photography. Great book!

Had one question - when using flash bounced of a wall etc what do you do with the flash's zoom? Leave it on auto or is it better to pick a particular zoom length?

Thanks

Ian

Comments

  • AllenAllen Member
    edited January 2011
    Hi Ian. This is one of those "it depends" questions. If you find that "auto" delivers the results you require and your battery life/recycle time is OK, then leave it alone. If, however, using your choice of aperture and ISO settings, you reach the limits of your flash, then you should consider using manual zoom. There is no particular zoom setting to use... it just needs to be long enough to give the range you need and wide enough to give the coverage you need.

    My Canon 430EX II has a guide no. of 43m @ 100 ISO @ 105mm which is OK (for me) for normal use, but when I move the flash head away from the straight ahead position, it automatically zooms to 35mm, which reduces the guide no. to 31m @ 100 ISO. If my flash-to-subject (via the wall) distance is large, I have no choice but to zoom. I don't procrastinate - I usually go straight for the max. 105mm.
  • Neil vNNeil vN Administrator
    irose ... I usually zoom to the tightest setting my flash allows. Doing so gives more reach to the flash. The range actually improves.

    I would have to do some testing though to see if this really does affect the image brightness in a really large venue vs working in a smaller room.
  • Thanks Neil and Allen. Advice appreciated.

    Ian
  • Thanks to the op for asking the question, this was something i also was wondering (bugging me) but couldn't find an answer to. Now that I have that answer, I’ve got more questions!! (It never ends :))

    Allen - great explanation, Thanks.

    Neil (& others)- I know you say "usually zoom to the tightest setting" so would this be your 'default setting' for bounce regardless of venue/environment?

    I'm guessing that in a smaller environment or when the bounce surface is closer to the flash at full zoom then there could be a noticeable difference in light fall off and softness? or is this a non issue in most cases?

    I'm asking questions that are (currently) beyond my ability however I’m intrigued...

    Thanks
    Chris
  • Ed Verosky aptly describes the the physical behavior of the flash light at various zooms:
    http://www.about-photography.com/2010/06/light-dispersal-pattern-of-a-flash-unit/

    So, setting the zoom on the flash creates a narrower beam of light. This makes it easier to target a bounce surface and ensure a large of amount of this light will bounce off.

    I normally set my flash to the maximum zoom settings when I am bouncing indoors.
  • Thanks Stephen for the link and your feedback, very much appreciated.
    This is just another reason why i love photography.. you open one door only to find two more.

    and guess what.. iv'e got another question :)

    Its all in the details. Another tip/technique added to the bag.
    Cheers.
    Chris

  • Neil vNNeil vN Administrator
    Ed Verosky's comparison is obviously for direct flash. With bounce flash, this pretty much disappears. You have a much larger light source. A massive softbox behind you, whether you have your flash zoomed tight or wide.
  • Neil,
    You have mentioned in past blog posts that you have shot with the flash zoom at maximum. Based on your response here, I am now confused as to what occasions you need to use a zoomed tight flash. Is it simply to save power on the flash?

    My understanding is that zoomed tight flash beam means a concentrated beam of light hitting the bounce surface. This means more light rays reach the bounce surface to be reflected, especially if the bounce surface is noticeably far away. I'm only referring to the incident light striking the bounce surface, not the reflected light.
  • Neil vNNeil vN Administrator
    Stephen ... that's arm-chair theorizing. What does it actually look like when you do it?
  • Neil, you got me on this one. The longest distance between my flash head and a bounce surface that I ever tried was 8 feet. At that distance, the bounced flash didn't really change the image, whether the incident flash was zoomed wide or tight. I was thinking the flash head zoom would matter for distances greater than 8 feet, but that probably isn't a very practical range. Since you've shot a lot more than me, I defer to your experience.

    Sorry! Despite improvement in some areas, I still get hung up with numbers and theories. I appreciate you reminding me that it's not all numbers and theories.
  • I'm finding that Allens "it depends" comment to be about right once all other factors are considered. While i knew that there was never going to be a single setting to use, i was looking for (and found) the "usually" setting for best results.

    From my personal experience, I'm finding that the lens focal length is also plays a contributing factor. If i shoot with a wide'ish lens with the flash (bounced) zoomed then this can cause uneven lighting on the subject if the bounce source is relativly close to the flash. If i swap to a 50mm or greater, due to the narrower field of view, it works.

    So in respect to flash zoom, when i'm bouncing flash i'm now thinking about: focal length, flash to subject distance (bounced surface), and the flash zoom setting which i am now "usually" zooming to max but it "depends".
    Thanks all for the tips.
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