Quick Setup Guide for MEC-5-FSL D3400-N85 Miles Eye Camera
6
Getting Correct Exposure
Using Auto-Exposure (Recommended)
1.
The camera is shipped with
Auto-Exposure
, via the Control for Built-in Flash set to the TTL
(Through-the Lens) setting in the Set-Up Menu. In this auto-exposure mode, the flash will
automatically be adjusted for a good exposure. The aperture should be in the range of f/16 to f/22.
2.
This camera-lens-illuminator is optimized for autoexposure photography of the iris; it is especially
easy to take consistently good iris images when using the Auto-Exposure Flash Mode. In this mode the
flash power is adjusted by the camera to give a suitable exposure regardless of the aperture setting.
3.
There is a tradeoff between the sharpness of a lower aperture such as 5.6 thru f/20 (sharpness improves
with a lower f/number) due to less diffraction blurring when the aperture is at the lower number, and
the depth of field, which becomes to small to get the entire iris in focus when the aperture is less than
f/16. Consequently the best overall sharpness for iris photography is between f/16 and f/25.
4.
With Auto-Exposure you can dial in whatever aperture you want, but best results will be found within
this range of f/16 and f/25. Miles Research recommends f/22 for iris photography.
5.
For sclera photography, having the larger depth of field is very important in order to get the entire
visible surface of the sclera (including the bulbar conjunctival vessels) in focus, so the recommended
aperture for scleral photography is the maximum aperture value – normally (with the 85mm lens) at
f/45.
Using Manual Exposure (for the Advanced User)
6.
It is also possible to use
Manual Exposure
where the aperture can be adjusted through a range of
values and the best exposure later selected from the series of photos. For this manual exposure, set the
Flash Mode
to
Manual (1/2 Power)
. To see how the camera settings can be changed, see Section L,
Reference for Nikon D3200 Camera Settings (page 35).
7.
Use the main command dial at the upper rear of the camera for
adjusting the aperture
.
The Main Command Dial is operated with the right thumb
and is used to adjust aperture. Normally, the best practice is
to take 3 or 4 pictures of each iris, each picture shot with a
different consecutive aperture.
The
aperture dial
(situated where the right thumb would
be when holding the camera with the right hand) is
changed by the thumb; clicking the wheel
inboard (to left)
decreases
aperture number and clicking the wheel
outboard (to the right) increases
it. Larger aperture
values mean smaller aperture diameter -- less light will be
allowed in. Images with higher f/numbers will be darker
than those taken with lower f/numbers
8.
Note:
When using Auto-Exposure (Flash mode on TTL), you can set the aperture to any value without
affecting the exposure. However to get sufficient depth of field, set the aperture to f/20 (any value in
the range of f/16 thru f/32 will give good results).
For photographing sclera
, always use f/45.
