[Tfug] Way OT: optics mumbo jumbo

[Bexley Hall]

Hi, Joe,

--- jblais <joe.blais at pti-instruments.com> wrote:

> There used to "guide numbers" for flash units
> (before they were integrated
> in the body of the camera).  You'd take the guide
> number and divide by feet,
> and for a given ASA (ISO) number, that would give
> you the f: number.  The
> flash usually is much faster than a shutter, so 35mm
> film camers had a
> "sync" speed for the vaarious types of flash
> (electronic / bulb).  Newer
> flash devices had a sensor that would turn off the
> flash when it sensed
> enough light.  Through-the lens sensor and CCD
> imaging - I don't know where
> the ontrol is.

OK.
 
> The distance from the source to the subject is the
> critical thing for
> lighting.  The camera can be anywhere.

OK.  And, in my case, the "source" is *on* the
camera!  :-/
 
> If you can separate the flash from the camera, put
> it off to a side, perhaps
> put a handkerchief over it, or even aim it at the
> ceiling, or backwards onto
> a white card, and let that reflection illuminate the
> subject.  You may want
> to play with exposure until you get it good, but  a
> new CCD camera may
> figure it out.  No flash, and good exposure, with a
> fairly bright, steady,
> even, light will be better than any flash.  If you
> can, take the thing you
> want to photograph and put it by a windoe facing
> north, or go on the north
> side of a building (plenty of light, no harsh
> shadows)-- reflected light is
> a good thing.

If I *remember* to take  my photos during the *day*,
I usually have no problem.  We have *lots* of light
here (one wall of the house is essentially glass,
floor to ceiling).

The problem is that I do a lot of work late at night.
So, I have to rely on artificial light.

For small items, I like to set them on a "flat file"
in the "family room" as it is a nice, large, solid
surface at ~waist height  (i.e., 3.5' x 4.5' x 3ft
tall).  So, I can squat a little to get shots
"dead on".  Or, stand right by the cabinet to shoot
*down* onto the target, etc.

The problem is the lighting in that room is from
fixtures recessed in the ceiling, angled off the
walls (indirect).  Since the flat file is so
damn *big* (i.e., I am standing 3.5 ft from the
wall when I stand beside it), this results in
most of the light falling behind the target.
Which leaves me no choice but to use a flash
(or, wait until the next day and HOPE that I
remember to shoot during daylight hours!)
  
> Some cameras have a built in flash that can be aimed
> at the ceiling.  Or
> just tape a piece of paper over the flash when you
> do closeups.
> 
> There are copy stands and such that hold light at 45
> deg. to the line of
> sight.  Nikon also used to make a ring flash and a
> macro lens with a built
> in ring flash for very good close ups.

If I used my 35mm I would probably end up with
better pictures with less effort -- but, then I
lose the immediacy of being able to email them,
etc.

Clearly, the solution is to come up with better
lighting in that room.  Or, find some other
room that *has* better lighting (living room is
bright as day at night but harder to "pose" the
objects as there isn't really anything to set them
on)



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