Why It Is Bad To Underexpose In Low Light

rhino adult and child

I shot this on auto-ISO, which means that I let the camera determine the ISO while I shot at the shutter speed and aperture at which I wanted to shoot.

The ISO was 4,000 because the light was very low in the late afternoon into evening. Still, something went wrong because the RAW file is underexposed by almost two stops. Here is the default, uncorrected setting:


When the light is low, the camera is very unforgiving if the photo is underexposed. I am not sure what caused it to underexpose, maybe the settings hit the buffers and it couldn’t expose enough for the limits I had placed on shutter speed.

What I mean by unforgiving is that when I open up the exposure in Photoshop, there is a lot of grain in the photo. You can see it in the corrected version at the top, and more so in this crop.


So What Is A ‘Stop’?

A ‘stop’ is a halving or doubling (depending on which way you are going) of the light entering the camera compared to the value of the adjacent ‘f-stop’

The standard ‘f-stop’ settings run something like f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22

And if you photograph, you may well have a lens with a maximum aperture of f1.8, which is a half-stop position.

So, for example, f2.8 lets in twice of much light as shooting with the same shutter speed and ISO at f4.

That’s why professional photographers use lenses that have wide maximum apertures such as f 2.8 or even f2.0 or f1.4. That gives them more freedom to use a lower ISO and/or a faster shutter speed.

The ‘problem’ with lenses with fast apertures, especially long focal length lenses is that there is more glass of greater diameter in them – and glass is heavy. Here for comparison are the weights of a couple of 300mm lenses. Of course, the f2.8 lens has more light-gathering power, but at the cost of size and weight.

AF-S NIKKOR 300mm f4E PF ED VR 755g (26 ounces)

AF-S NIKKOR 300mm f2.8 G ED VR II 2,900g (102 ounces)

Oh Oh, What’s Going On?


zebra in south africa

This is the sixteenth in a series of photos I took from a vehicle on a trail in South Africa. The air was very still and it was very quiet.

Up to that point the zebras had been in various states of unaware and mildly curious. Then it changed. And I think it was the sound of the shutter on the camera that put this zebra on alert with a look of ‘Oh oh, what’s going on?’

Looking back now, I wondered how far I was from the animal. And I think I have been able to work it out, more or less.

The EXIF information on the camera said that the focal length of the lens was 300mm. That’s the maximum reach of that lens. I was shooting with a Nikon D500 camera, which has a DX format sensor, meaning that it is 1:1.5 ratio compared to a full-frame sensor.

And what that means is that a 300mm focal length has a reach of 450mm in full-frame equivalent.

With that information, I looked up the angle of view tables for Nikon cameras and lenses. For a DX camera at 300mm and it said that the horizontal angle of view is 4.5°.

You can imagine two narrow lines reaching out from the lens with an angle of 4.5° between the lines. At some distance they will cover the horizontal length that is in the frame of this photograph. What is that distance?

From looking at the photo I estimated the length of the animal and the space either side at 4.25m (14 feet). Finally, I input that information into an angular size calculator and it gave me a distance of 54.5m (178 feet) from my camera to the zebra.

So, could the zebra hear the camera shutter 54.5m (178 feet) away? Oh yes, definitely.

Why Camera Shutters Make A Sound

It depends on the kind of camera. Little point and shoots are often silent. On the other hand I had a Panasonic GF1 that sounded like someone wheezing. I don’t think there was any reason it had to make a sound, just something the manufacturer built in.

But dSLRs like the Nikon D500 make a noise because of their construction. ‘SLR’ stands for single lens reflex. and dSLR stands simply for digital single lens reflex. And whether film or digital, the principle is practically the same.

SLRs are called ‘reflex’ cameras because of the mirror that diverts the light that comes through the lens. and sends it up to the viewfinder.

Looking through the viewfinder of an SLR is like looking through a periscope in a submarine; it’s just that the periscope is only a half an inch tall.

When you press the shutter to take a photo, the mirror flips up out of the way to allow the light to reach the sensor. Then it flips back down again. That’s the reflex.

And even though camera manufacturers dampen the mirror when it flicks up and down, it still makes a noise – and I think that is what the zebra heard.

Mirrorless cameras can have silent shutters. And that is one of the reasons that photographers shooting wildlife are using mirrorless cameras more and more.

There is another reason why mirrorless cameras are replacing dSLRs. That is without a mirror to flip up and out of the way and back again, the camera can fire more rapidly.

The Nikon D500 is a fast camera. It acquires focus quickly and it can fire off 10 frames in a second. But some mirrorless cameras can fire at twice that rate. And that is important to wildlife photographers.

Imagine, there is the bird ready to take off or about to dive into the water. At 20 frames per second the photographer can pick the best of a series of frames. And he or she can be pretty sure that one of the frames at least will show the bird to perfection.

A third reason why mirrorless cameras are becoming more popular for photographing wildlife is again to do with the mirror on dSLRs. Each time the shutter fires on a dSLR, the mirror flips out of the way, as we have said. And when it flips out of the way, the optical viewfinder goes black. Imagine that little periscope and the mirror moving out of the way and not letting light travel to the eye.

So Why Are dSLRs Still Popular

It’s precisely because the viewfinder in a dSLR is an optical viewfinder that keeps some photographers attached to using them. The view in the viewfinder of a mirrorless camera is a digital representation of the scene. And some photographers feel that robs them of an immediacy that is part of the reason they are photographing in the first place.

The tables I Used To Calculate The Distance

Field Of View

Angular Size

Nepali Women With Festival Offerings

Nepali women with offerings during a festival

Now that I have changed the WordPress theme, the maximum size of the image is smaller. But… click the image to see a bigger version!

How different each person is from the next – different appearance, different attitudes to the moment, but all making the effort.

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