Tag Archives: Side light

What good is a lens hood?

Five Types Of Lens Hood

• Five Types Of Lens Hood •
Attribution: Photo of five lens hoods for a mix of lenses; March 2013; Author: Geni; Permission: GFDL CC-BY-SA

Using a lens hood is important.

It is not always clear why we need a lens hood. Why do we need them and what are they for? Actually they are pretty important and can help prevent some nasty visual artefacts.

What is going on in the lens

Normally photographic lenses perform really well. They receive light reflected from your subject as parallel beams. These are focused by the lens into an image formed on the digital image sensor.

When light hits the lens from the side the situation is slightly different. Some of the light is refracted through the lens correctly. Some of the light however, is reflected off the surface and lost. But there is a percentage of light that goes astray in the lens. It can be bounced around in the lens – reflecting around from the surfaces of different lens elements internally. If it does so, on each reflection some of the light will get through to the sensor. Each time that happens there will be a slightly side-shifted ghost image. All sorts of light aberrations can be created by this internal reflection in the lens. It is these that cause the artefacts you see in the image.

Light is also scattered by inconsistencies in the lens glass. Chemical, and structural variations in the glass can impact on the way the light travels through the lens. This scatter contributes to the problem. These artefacts, and often an associated haze, are called lens flare and can be worse the further to the side that the light enters the lens. Flare and haze will not only form a distraction but also act to wash out the colours in your shot and reduce contrasts. These will make your picture look flat and lifeless. Unintended flare can simply kill the effectiveness of the shot.

A sharp angle of side-light can therefore cause all sorts of visual image ghosts which are not there in the scene. You can see a range of different types of flare in this Google image search…
Google images: Example lens flare images  External link - opens new tab/page

In general, poor quality glass and multiple elements in the photographic lens will tend to create more flare. Of course better lenses (read: “more expensive”) can help to reduce the problem. Higher quality lenses will incorporate a range of ways to reduce the problem. These include optimised lens-element design, surface coatings and non-reflective surfaces/parts internally as well as high quality glass. Despite that no lens is immune to flare.

What does a lens hood do?

The most common reason we use a lens hood is to reduce the incidence of a bright light source hitting the lens from the side. This will act to reduce the chance that the lens will suffer from the flare problem. In other words, the hood will help to keep the light coming in from the front of the lens in parallel rays.

It is simple really. Put up a wall at the side and the side light is cut out. However, it is not so simple to design a lens hood that will do that without obstructing the lens. The field of view of the lens cannot be allowed to catch the hood sides. If it does it will leave its mark on the image. So all sorts of hood shapes and sizes are required to match the visual characteristics of the lens. Lens hoods are quirky shapes because they have been designed to optimally reduce the side incidence of light and not interfere with the field of view.

Common design elements include “petal” shaped edges. These allow the corners of the sensor a wide field of view without interference in the corners from the hood. The long petal shape must be along the long side of the sensor (landscape view). If you put it on the other way the side of the picture will show the edge of the hood and light will also get in from the top (or bottom) because the cover is insufficient there.

There are conical shapes and cylindrical shapes too. When these don’t have petals they are designed to accommodate the full field of view of the lens from any angle. You may find that these types of hoods are common on lenses where the front of the lens extends when changing focal length. As the extension of the lens will change the field of view the hood shape must be wide enough for the widest angle of view. But it cannot have petals because they would rotate with the lens and at some focal lengths would interfere in the picture.

Lens hoods do more…

As you can see you should buy a hood for your lens that has specially been designed for it. If you don’t, you risk the hood intruding in your shot, or not providing sufficient protection against flare.

Hoods can help in other ways too. When you have a lens hood on the lens it acts as a primary protection for your vulnerable front element. Once, when I was panning to follow a bird with a heavy/expensive pro-zoom lens I whacked the lens hood off the glass of my car window. I am convinced I would have broken the window and damaged the front lens element if I had not had a lens hood on. It harmlessly bounced. Phew! I use hoods whenever I can these days.

Lens hoods also help to reduce over exposure generally from incident reflected light on bright days. There may be no direct bright light source shining into your lens. But it helps to reduce the high levels of brightness from the side regardless. That helps to reduce the overall high light levels and especially the contrast.

Lens hoods are worth the effort

Lots of learner photographers forget the lens hood. Yet it can have quite a significant impact. Even if it is not significant, when you are trying to get a sharp image and reduce the colour wash-out in bright light every little detail counts. Great images come from the attention to detail.

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By Damon Guy (author and Photokonnexion editor)

Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photographers.
See also: Editors ‘Bio’.
See also: Profile on Google+.

Sidelight – How to capture great texture in your photographs

Rippled Sand • Sidelight creates a lovely texture

• Rippled Sand •
Beautiful soft sidelight from bottom left creates lovely shadows after each ripple. Had the shot been taken with flash from above, the ripples would have been near invisible.
Rippled sand by Seldom Scene Photography, on FlickrExternal link - opens new tab/page

The capture of texture depends on the angle of light.

It is that simple. The lower you get your light to the side of your subject the more you will create shadows that stand out. Photographers have long recognised the benefit of long shadows for their definition in landscapes. Beside the great colours of sunset, the long shadows from sidelight provide character and definition to the landscape.

The same idea can be applied to the much smaller scale. Still life, studio set-ups and even drying paint can all be enhanced by sidelight. When working with smaller subjects, “get in tight and sidelight” is great advice.

Vintage Store Photo Challenge

This is the best video I have seen on working with smaller objects and side lighting. Gavin Hoey explains with an off-camera flash how to bring out texture and detail in still life photos. This is a very simple lesson. After seeing it you will want to explore side lighting further.

After the video there are some more resources on the subject…

 

Approaching sidelight with your images

In the video Gavin Hoey used a diffused speedlight, off-camera flash. In the post “Off-camera flash” you can find out all about what they are and the functions they provide.

If you want to improve your off-camera flash working with some sort of diffuser is a great idea. I have worked with a range of off-camera flash diffusers over the years and often been disappointed. I am really enthusiastic about the Rogue Flashbender range of diffusers. I use the Large Rogue Flashbender and the diffuser to go with it for work and my own projects. It is an exceptionally flexible piece of kit and occupies only a tiny space in your kitbag since it rolls up very tightly. The whole Rogue Flashbender range are great products and worth checking out.

One of the great tools I keep within reach when doing table top photography is the little LED light unit below. Designed for camping it has become a great light for my table top product work. It is small, adaptable and very cheap to run as it uses very little battery power.

I have two of these and place them on the table lying down or on end. The light itself is quite white so it will not give you colour casts. If the light is too harsh I just cover the LED panel with tracing paper or ordinary (white) toilet tissue. The tissue-light is gorgeous, soft and easy to use. These are excellent products and inexpensive to buy. They are probably the simplest way to set up a table top sidelight.

Working with people, stronger light gives you more control over freezing your subject. For portrait work a flash helps. To freeze a portrait for a sharp picture use a brighter light and a short exposure. A side-lit portrait is 100% better than a pop-up flash shot where the light is straight on. For this, the off-camera flash is the way to go. You have the flexibility to create a sidelight that creates shadows that define the face. Make the light as soft as possible so the shadows wrap around. Avoid hard or harsh shadow lines on faces. It is not flattering.

At the other end of the scale the low intensity light of the LED panels allows for long exposures when using static subjects. Use a longer shutter time if you want your subject to be lit more brightly. Of course to do that you will need a way of steadying your camera for long exposures. A tripod is probably best in this situation.

The way to go…

In the wilds, or doing table-top studies the best light comes in from a shallow angle as sidelight. It is the shadows that define objects and bring out strong textures. Look for side lighting where ever you can, and create it yourself if the natural light can’t do it for you.

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By Damon Guy (author and Photokonnexion editor)

Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photographers.
See also: Editors ‘Bio’.
See also: Profile on Google+.

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