Well, I mostly agree with Ken. We certainly agree with keeping a fixed
distance but not on the point of recommending a prime lens. Nothing
wrong with a prime lens but, since you're trying to maintain exposure by
keeping a constant distance, the use of a zoom allows you to frame the
subject without changing your distance by zooming with your feet. But
the only sort of zoom that's appropriate for this type of work is a
constant aperture zoom or else you must always use an aperture that is
at least as small as the minimum size when the lens is at full
telephoto. In other words, if I were using my Tamron 24-135/3.5-5.6 I
would never set an aperture of f/4 since the Tamron is only good for f/4
up to about 35mm. Zooming the lens to a longer focal length could
suddenly find the lens limited to its smallest aperture of f/5.6 and an
inadvertent under-exposure of 1 stop. If I'm shooting manual flash
indoors the lens I use is the Tokina 28-80/2.8.
Dr. Flash
On 5/20/2011 10:13 AM, Ken Norton wrote:
>> Dr Flash's comments are duly noted and appreciated. I can understand
>> that manual works extremely well in a studio or fairly static
>> environment (inside or outside). I suspect that it's more cumbersome for
>> ad hoc shooting - street shots (e.g., my Chinese night market shots) and
>> "parties/gatherings". I can also see how using manual is easier with
>> digital than with film.
>
>
> Not trying to beat Chuck to the punch, but let me comment on this.
>
> Probably the ONLY time I can think of where auto-flash is truly easier is
> when the flash-to-subject distance is constantly changing Otherwise, it can
> actually be a hindrance rather than a help. One of the best ways to make
> manual-flash work easier for you is to avoid usage of a zoom lens. When you
> have a prime lens on the camera, you do tend to shoot from a relatively
> fixed camera-to-subject distance. For me, that's around one body-length,
> sometimes two body-lengths. This is why a 35mm focal length works so well
> for me.
>
> The key to survival is the exposure guide that's somehow mounted or printed
> on the flash itself. It gives you a triangulated calculation of ISO,
> Aperture and Distance. If you are shooting ISO 100 and the subject is 4
> meters distance, it's an easy thing to glance at flash to know what aperture
> to choose.
>
> Really, flash calculations as well as fill-flash calculations are a matter
> of simple algebra. The idea is to define as many variables as you can so it
> leaves just one letter to calculate for. Sometimes this is a reiterative
> process. Assuming your Pen-F for a minute:
>
> For the given flash-to-subject distance (which is the same as
> camera-to-subject distance for on-camera flash), we always start with ISO.
> What is the film-speed of what is loaded in the camera? ISO 100? Great. We
> can work with that.
>
> Secondly, what is the distance to the subject? Since you are using a prime
> lens which may force you to a given camera-to-subject distance, let's say
> for this discussion it's 2 meters distance. OK, that gives us two out of the
> three things needed for flash exposure. Looking at the on-flash calculator,
> we see that the flash at ISO 100 and 3m distance requires F5.6. (or
> whatever, but this is my story).
>
> You adjust the camera lens to F5.6. That takes care of two of the three
> camera settings. We have ISO, we have aperture, but now we need
> shutter-speed. Since this is the Pen-F, we can choose any supported speed.
> So, we meter the scene and decide we want the background to be -2 stops. But
> the exposure meter says that a normal exposure of the background is ISO 100,
> F5.6 and 1/4 of a second. Subtracting two stops from that means we either
> adjust the ISO, the aperture or the shutter speed. Since we are shooting
> film, the ISO is fixed. Can't change that. The aperture is determined by the
> flash calculator, so we can't change that. So we get to adjust the shutter
> speed instead! In this example, a proper (non-flash) exposure of the
> background requires 1/4 of a second, so we subtract two from that going to
> 1/16 of a second....
>
> OK, you are right. Auto flash is easier...
>
> AG
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