[net.rec.photo] How to use a flash

kathleen (01/14/83)

Whoever wrote the article about using a flash didn't state whether or not
they had an adjustable flash head.  If so, the flash burn in the eyes is
easily corrected.  Simply tilt up the head of the flash and use it in a
bounce position.  You may have to open up a half a stop on your camera to
compensate for the bounce.  If your flash head is not adjustable, there are
still ways to diffuse the flash.  You could purchase a diffuser from a camera
store to fit over the flash or you could rubberband a piece of white cloth
over the head and use the flash in this manner.  You would have to experiment
with the flash to determine the amount of stops to compensate for the diffusion,but it would be to your advantage to do this.  Perhaps by using a smaller
size roll of film for this experiment, you could keeps costs down.

Happy shooting!!

Katie

prgclb (01/14/83)

I think the red spots in the eyes when taking flash pix
are due to illumination of the persons' retinas.
Can anyone confirm/deny?

Of course, this will only happen when the flash is very
close to the lens, like on instamatics.  That's why
people with outboard flashes on their 35mm SLRs don't
have the problem -- not because they're pros, but because
the flash will be several inches from the lens.

				Carl Blesch
				Bell Labs - Naperville, Ill.
				IH 2A-159, (312) 979-3360
				ihuxm!prgclb

gjm (01/14/83)

The strange appearence of people's eyes in many flash photos is typically
referred to as "red eye".  This condidtion is caused by direct reflection of
the flash off of the retina.  "Red eye" is most apparent when the flash
to subject's eye path is nearly parallel to the path of the reflected light
from the subject's eye to the camera lens.

So tilting the flash head for bounce as Katie suggests will eliminate the
condition, but also cuts down on the effective range of the flash unit (less
of the light output from the flash reaches the subject).  If you are indoor
with good reflecting ceilings and walls, bounce should be an effective
measure with even pleasing effects.  However, it is ineffective outdoors
because of the lack of reflecting surfaces.

The standard way to reduce "red eye" is to move the flash source "off center"
away from the lense as far as necessary (or possible).  This is why some
of the pocket 110 cameras supply you with a stalk to mount the flash cube
away from the lense.  Bracket mounts or flash extensions can also be used,
but you must be aware that many flash sensors are attached to the flash head,
so moving the unit also means moving the sensor away from the lense (where it
is the most accurate).  Many flash systems offer "remote sensors" to mount
on the camera for off-camera flash.

Note that it is the angle that is critical, so close subject usually have
less problem with "red eye", while subjects at longer flash ranges require
the flash to be farther off-camera to eliminate the condition.

Gary Murakami
ihnp4!gjm

halle1 (01/15/83)

The problem still exists if the flash is mounted on the SLR, although it is
not as bad.  It must be removed several more inches to stop the redeye.

nrf (01/15/83)

another way to reduce 'red-eye' is to provide additional light in the room
if possible so the subjects pupils contract further.

dmmartindale (01/16/83)

You get the red-eye effect whenever the flash and camera lens are within
a small enough angle of each other from the point of view of the subject.
The darker the room and thus the wider their pupils are, the greater this
angle can be and still get the effect.  But it simply angle that matters,
not absolute distance of flash from the camera lens - I've gotten redeye
in pictures taken with a telephoto lens where the flashtube was 6-8 inches
away from the lens, but when the subject is 30 feet away that isn't much of
an angle.

jhillis (01/17/83)

RE: redeye

Rinse the prints in murine

rs55611 (01/20/83)

Several people have recommended using bounce flash (tilted flash head)
as a means to eliminate "redeye", mentioning in their responses that
there is a loss of flash intensity that must be compensated for.
Some clarification is needed.  First, with automatic flashes, no
compensation is needed, as the light coming back to the flash sensor
has already bounced off the ceiling, and is therefore already less intense.
Thus, the flash (or the camera, in the case of TTL flash metering, as
on Minolta x-700) will automatically adjust for the bounce flash.
The thing which you have to be aware of is that the maximum flash
to subject distance over which the auto-flash will work properly has been
reduced.  Most auto-flashes with bounce heads have an indication on the
table on the back of the flash which shows maximum distance as a function
of film speed (this also shows the appropriate aperture for each film speed).
This table will often also show a reduced maximum distance when using bounce
flash (automatic mode only)  Aperture compensation at the camera is only needed
for manual flash mode.  Another warning:  Pictures taken with bounce flash
can be discolored if the surface that the flash bounces off of (prior to
getting to the subject) is colored.  Thus, bounce flash off of a white
ceiling works, while bouncing off of a painted wall (holding the camera
vertically, for instance) will cause coloration.  (Off-white ceilings
give a nice warming effect.)  Diffusers placed over the flash head
avoid this, and will also be automatically compensated for by
auto-flash operation.

Bob Schleicher
ihuxk!rs55611