Understanding your Digital Camera (Part1)

Hi, today I tackle another Photo Technical subject. Do you really understand the controls on your digital camera? I will try to explain them to you in this series of Photo blogs.

Most cameras have a circular wheel type Mode switch with symbols and/or letters on it.

Today I will deal with M (Manual) vs P (Programmed or Auto) and ISO settings.

M, or manual mode, provides the most versatility to the photographer. In this mode the photographer can decide how to take the picture, whether depth of field is important, or freeze motion. Different subjects demand different settings.

Sometimes it is important to be able to control the amount of light coming into the sensor. For example in P or auto mode the camera will decide on the best exposure for the given scene, however, the photographer may want to under- or over expose the subject and/or surroundings depending on what needs to be highlighted in the picture. Auto (P) will usually not allow a picture to be taken if the exposure is not correct within it’s parameters.

There are other Automatic modes you could use. They are:

Shutter priority: setting the shutter speed to, say, 1/1000 second. The camera chooses the appropriate Aperture for the selected shutter speed.

Aperture Priority: setting the Aperture (lens or iris opening) to, say, f/4.5. the camera chooses the most appropriate shutter speed for the given scene.

What is ISO? It is short for International Organization for Standardization. In photography there is an ISO standard for Film Speed, or in digital photography terms the sensor’s sensitivity to light. In earlier years there was the ASA, or, American Standards Association, which defined film speed. ASA is no longer the accepted standard and ISO is in it’s place.

Film manufactures would make films of varying ASA. This would mean the sensitivity of the actual film to light. Normal outdoor shooting on a sunny day would require an ASA film of 80 or 100. This is a “slow” film. Sunny conditions provide enough light for the image to be captured smoothly and efficiently with low grain quaility.  The label on the film box would indicate the film’s  ASA value as 80, and one would have to set your camera accordingly. A lower number (80 or 100) would indicate that the film is a low speed film and could be used in sunny conditions. in other words higher apertures (smaller iris or lens openings) are possible because of the abundance of light. In dusky conditions or at night with street light, a “faster” film (more sensitive to light) would be required such as ASA 400 or greater depending on the availability of light. Each time the camera would have to be set to the type of film being used. The higher the ASA number though, the grainier the resulting picture would be.

These days with digital technology, things are easier. The ISO setting determines the Sensor’s sensitivity to light. Simply dialling in the ISO number appropriate to the surrounding light for the scene set the camera up to take pictures in low light conditions. BUT as in film cameras there is also a downside to high ISO numbers. The higher the number, the “noisier” the resulting image. Digital noise is the appearance of random dots of colour in an image that should be smooth. Some photographers use this deliberately to achieve a grainy quality to their photographs, but mostly it is undesirable and is avoided by using as low an ISO as possible. Different sensor manufacturer’s manage to produce sensors of varying noise production. The more expensive the camera, the less noise is produced at the higher end of the ISO range.

Using the P or Auto mode will allow the camera to decide on the appropriate ISO setting to be used in any given scene. If the ISO mode is set to AUTO It will automatically select an ISO value that gives the best use of available light. To avoid high noise, set the ISO to as low as possible for the given light situation.

Why would you want to change the ISO setting? Well in low light situations where you do not have a tripod to steady the camera, you can increase the light sensitivity of the sensor by increasing the ISO thus increasing the light to the sensor enabling a higher shutter speed. This results in less blur due to camera motion. See the last example photo of the cats. Notice it is blurred? That is because the ISO was too low, for the available light. To expose it correctly I had to drop the shutter speed to 0.80 second. This photo should actually have been taken using a tripod to steady the camera, or by increasing the ISO level.

In wild life photography, many times the animal being photographed is standing in the shade between trees. A long lens, like my Sigma 500mm zoom, can reach the animal quite adequately but is not a good performer under low light conditions. Increasing the ISO helps the lens achieve a reasonable amount of light for the sensor.

To answer the question: “Is Manual mode better than Auto mode?”. See the 3 pictures of the milk urns  – all are correctly exposed, but taken with different settings. The 1st one was taken using auto mode, the other 2 were taken manually but by fiddling with the ISO level.

The answer is quite simple really, no, it is not better and neither is it worse. It really depends on the situation. See the 3 pictures of the milk urns  – all are correctly exposed, but taken with different settings. The 1st one was taken using auto mode, the other 2 were taken manually but by fiddling with the ISO level.

If you are in the situation where you need to change settings rapidly to capture variable light scenarios, then Auto mode is probably the better approach. If you have time to experiment and evaluate the situation then I would suggest manual mode as this gives you more versatility and that is better for creativity.

There are many books covering this complex topic, but I hope I have managed to clear up some of the mystery surrounding the use of Manual mode vs Auto mode.

Finally, don’t be afraid of using the manual mode. The more you use it the better your images will become. Guaranteed.


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