Todays SLR’s have several modes of operation besides just auto. If your SLR does than this article might help you to shoot in the other modes.
Using auto mode is ok for simple snaps but if you want to move your photography experience to a higher level, you’ll need to change from auto to aperture or manual modes. For example, to capture birds, or fast moving objects you will need a fast shutter speed. If your subjects are birds for example not only is a High shutter speed required but an f-stop of f/8-f/16 may be required to control depth of field. A large f-number allows for a greater depth of focus from a small f-number. You don’t want to get the shot of the year and find it’s out of focus!
Most of the time I shoot in aperture mode to control my depth of field. On my Nikon D610 I can fix my shutter speed to be a minimum of 1/800 sec. and let the camera decide the ISO if I set ISO sensitivity control off, otherwise I can switch it on and fix it at a desirable setting depending on the lighting conditions. The trouble with shooting animals in or near the woods where lighting conditions can change dramatically you will need to setup your camera to handle settings quickly and to do that is to use the front and back wheels to change your settings quickly.
When I run in manual mode sometimes I am frustrated because the hysteresis graph shows over or under exposed images. I would like to do something different other than making changes to the camera settings continuously until the hysteresis graph becomes acceptable. To fix this problem I decided to find out what the relationship of aperture, shutter speed, and ISO are to each other. At first I did an empirical study where I shot in auto mode with a fixed ISO setting to see what was chosen for f-stop and shutter speed. I then went to aperture mode and set the f-stop from f/5.6 to f/64 and recorded the shutter speed. Then I updated the ISO and repeated the process. I pointed the camera at the same spot in the shade for one set of values and then on a subject out of the shade on a cloudy day and recorded the results. I transferred the results to Excel and built a graph to see visually what was going on.
The first thing I noticed is the smaller the f-stop, the shutter speed doesn’t change much and there is a significant difference between f/8 and f/16. What was really important is how it changed over a range of values. Notice how the shutter speed decreases as we increase the aperture value. The shutter speed decreases by half of the speed for each full aperture stop! Also as we double the ISO value, the shutter speed doubles. With this information we can calculate what the manual settings should be.
Adjusted Shutter Speed = Current Shutter Speed / 2n where n = number of full stops
New ISO = (Desired Shutter Speed/Adjusted Shutter Speed) * Current ISO
I snapped a picture of my grill on a heavy overcast day and the auto settings were 1/100 @f/4.5 with ISO of 400. If I wanted to shoot something at f/11 and a shutter speed of 1/1000 then,
Adjusted Shutter Speed = 100/ 23 or 100 / 2*2*2 = 12.5 New ISO = (1000/12.5) * 400 = 32000
On my Nikon I set the aperture to Hi 1. At the time I wasn’t sure what Hi 1 was so I snapped the picture.
Between the two shots I took photos of my Nikon hysteresis graph with my point and shoot Olympus Tough to compare hysteresis graphs and verify the data.
With a little more research I found information on what the Hi values represent in actual ISO for the Nikon D610 which is different for other models and manufacturers.
- HI 0.3 8300
- HI 0.7 10880
- HI 1 12800
- HI 2 25600
So here is the dilemma. I needed an ISO of 32,000 but Hi 1 is only 12,800? Well, the ISO setting of 25600 (Hi 1) according to the hysteresis caused the right side to shift to the left a little bit. Although the whites are not as white the hysteresis can be adjusted in post processing.
The other problem with High ISO’s is the introduction of color noise which may be reduced in post processing also.
The caveat here is you must know your limitations, max and min values of shutter speed, f/stop, and ISO settings. Pay attention to the hysteresis graph on your camera. When your hysteresis graph shows too much underexposed, black (left) or overexposed, white (right) changing the settings of your camera may help if your camera allows it.