August 5, 2020

Photography Myths Busted – Part 2

Last week we looked at three photography myths you shouldn’t believe. This week, we’ve got three more to debunk!

If you cast your mind back seven days, I revealed three well-held facts about photography that were not true. Because I like you all so much, I am going to explain another three similarly often voiced facts about taking pictures that were valid with old technology or just plain untrue!

A Histogram should look like a bell

Before we look at the myth, let’s remind ourselves what a histogram is. The histogram shows the distribution of brightness across the image captured on the sensor. The left-hand side of the histogram is pure black and the opposite edge, pure white. The height of the brightness histogram shows how much brightness there is as black moves through various shades of grey until it becomes white. The same is true when you look at an RGB histogram except it’s the distribution of the various shades of red, green or blue.

The myth is that the ideal shape for a histogram should be bell-shaped. There should be less brightness at the outer edges of the graph, the majority of the data bulges in the middle. Given what we know about how a histogram works, this is untrue. There can’t be a perfect shape to a histogram as the brightness will vary depending on the subject.

One of my favourite locations on the Switch to Manual workshop is down a little street off the Royal Mile called Sugarhouse Close. There’s a staircase going up the outside of a white building with each step and the handrails painted black. I don’t care what settings you use; there is no way that this scene is going to produce a histogram shaped like a bell. The dark blacks of the stairs and handrails will cluster toward the left of the histogram. The white walls will bunch toward the right of the histogram, and there’s very little of any other brightness in the picture. The exposure and histogram are correct; it’s the myth that is wrong

There’s more evidence that the myth is wrong thanks to something called exposing to the right. If you’re shooting in daylight, there is a benefit to bringing in more data toward the white end of the histogram.

The first image you can see was taken with the light meter recording a ‘correct’ exposure. The distribution on the histogram is pretty good, with all the data sitting between the two edges. Look at the right-hand side of the histogram. There’s a gap between the brightest part of the image and the far edge.

We can move the data toward the right by allowing more light to hit the sensor. In this case, we’ve made the shutter speed slower. This second image now looks a little brighter, and the histogram has shifted to the right. It still hasn’t got any clipping on the highlights, so all the data has been captured correctly.

Where we see the benefit of this approach is the amount of data that is collected. The first file, exposed ‘correctly’ contains 26.16mb of data. The second file has 27.67mb of data which gives us far more information to use when we start the editing process. You’ll see that there is a lot more detail in the shadow areas. In many images, you’ll also see a slight improvement in the overall sharpness too!

You should use a UV filter

A new photographer wandering into a camera shop to buy their first camera will usually leave with a camera, a kit lens, possibly a second zoom lens and memory cards – all justified purchases. A good salesperson will have foisted on the unwitting purchaser a UV or Skylight filter which adds another £30 onto the bill. The story will be that the UV filter will improve the photographs by making blues, bluer. They’ll also tell you that the filter is going to prevent your lenses from being damaged as they’ll take the brunt of a bang that would have usually cracked the front of your lens.

I’m going to admit that I’ll not show any images comparing a UV filter added to a lens versus the same picture without a UV filter. I don’t see the point in purchasing to prove something that should be obvious. Many years ago, lenses would have been produced with high-quality glass and then sent out for sale. This process may indeed have resulted in some UV light being diffracted, and a UV filter may have helped to restore some of the lost light. Today’s more modern lenses have several coatings that are just a few microns thick that improve the way light passes through the glass. The result is that the use of a UV filter will add nothing to the photos. It may actually have a detrimental effect. A cheap UV filter won’t have the same quality of glass as a relatively expensive lens so you’ll be putting inferior quality glass in front of excellent quality material.

The second selling point of the UV filter is that it will protect your expensive lenses from being scratched or smashed. Here I can use my personal experience. Part of my job as a photographer is shooting for the press. Every time there’s an election, press photographers spend six weeks of their lives following party leaders around. Often this is in tight, enclosed areas and there are a large number of photographers and film crews squeezed in with a fair bit of bumping and bashing to get the best shoot. In Scotland, we refer to this as a ‘rammy’ which is a great term! You’d think that if we aren’t using UV filters that we’d be making fairly regular trips to a camera retailer to replace damaged lenses. In eight years of doing that kind of photography, I haven’t experienced a single scratch on my lenses. Using a lens hood will give a far higher level of protection than a cheap piece of glass that would probably break into shards and scratch the lens anyway if it were damaged.

Switch image stabilisation off when using a tripod

Another regularly quoted myth of photography is that when you are shooting on a tripod, image stabilisation is turned off. The theory is that the motors are working to stabilise something which is already stable that they’ll vibrate to the extent that it will result in the image being blurry.

Let’s test the theory. I use two lenses that have image stabilisation built-in: the Canon 70-200mm f/2.8 L and the Canon 16-35mm f/4 L. This gives good coverage of focal distances, and I’ll take shots at a relatively fast and slow shutter speed to see if there is any variation. I’ve ruled out any outside influences by locking the mirror up, preventing vibration, and I used a shutter release cable.

Examine the photographs side by side, and there’s no difference in sharpness between any of them. The only discernible difference is a movement in the framing introduced through the act of switching on and off the image stabilisation. If there’s no difference between the photographs using wide or long zooms and at slow or fast shutter speeds there’s no need to switch stabilisation off when shooting with a tripod.

That completes this week’s debunking of myths. Next week we’ll have a final part to the series with not three but four more myths that need to be corrected. If you’ve got some things that you hear in photography which just aren’t true in practice, add them in the comments below and I’ll happily add to the collection!

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