These small pieces of plastic or metal, how good are they? Do they provide any protection to the lens? Are these good for photographs? Lens hoods are an often debated topic. They do help but sometimes they are very uncomfortable to use. Most of the new lenses are sold with a compatible hood now a days.
The stray light that may fall into the lens is an enemy of photographers at most times. This stray light gets scattered around the lens because of the multiple optical elements and presents itself as blobs of light arranged in a line. These blobs of light may look like circles, rings, starbursts or just irregular curved soft spots of light. Sometimes when the light source is far outside the coverage area of the lens, the flare will appear as a generalized lighted haze across the frame with resulting loss of saturation and contrast.
Hood, as the name says were initially intended to be simple shades for the lenses from stray light. Earlier lenses were quite prone for flare when light hit the optical elements and so preventing any stray light from hitting the optical elements was required. With the improvement in optics and their coatings, the problems with flare have been very nicely controlled. They are so well controlled that with most average lenses, photographers can directly point the lens at a bright source and click without the fear of flare. In spite of these advancements, the lenses are still prone to flare and the hoods can save the day.
Choose your lens hoods
Wide angle lens hoods
Now there is a catch to the hoods in wide-angle lenses. The wide-angle lenses are most prone for flare since they have a wide front element which is frequently placed very much towards the front. This exposes the lens surface to a lot of stray lights. The wide angle lenses being wide also have a greater chance of including some light sources in their angle of view. The hoods on the other hand can not be too protective. These have to be kept short to prevent encroaching on to the view and causing vignettes. Camera manufacturers have come out with the famous flower-petal hoods (or simply the petal-hoods) that shade the lens in a manner that is consistent with the rectangular image that is captured. They protrude into the image circle but are left out of the picture frame. The shape of petal hoods allows them to extend as far as possible beyond the lens without showing up in the frame. Very interesting. Now if you are planning to use this kind of hood, keep in mind to buy a bayonet mounting hood that aligns itself to the camera perfectly. Screw-mount petal hoods are a waste. These have to be kept loose and rotated to align with the image frame which can be an added effort. Also remember that in these petal hoods, changing the orientation of the camera from horizontal to vertical can change the amount of flare. The petals on the longer side of the frame protrude further out than the petals along the shorter side of the frame.
Normal and Tele lens hoods
With the normal lenses or telephotos, the front lens elements are usually quite recessed and since the angle of view is less, good long hoods can be easily used. Most of the hoods with tele lenses are like a cup. There is no variation in the edges like with petal hoods. These are called ’round lens hoods’. Round lens hoods do not pose a problem with alignment with respect to the film/sensor since they are round. These can be screw mounted or bayonet type.
Lens hoods on zoom lenses
This is a troublesome situation. The hoods provided as a standard with zoom lenses are manufactured so as to prevent their showing up in the frame at the widest end of the zoom lens. This makes these hoods quite inefficient for most of the zoom range. My recommendation is to buy an inexpensive after-market screw-on hood for the mid to the tele end of such zoom lenses.
Bayonet mount hoods and rotating filters
This is yet another problem. Sometimes I feel that the lens manufacturers are very good engineers but poor photographers. Have they every tried using a polarizing filter with their lenses having bayonet mount hoods. It’s a real pain. The longer the hood, the worse is the usability with filters that require rotation. Pentax had come out with lens hoods that had a small sliding window to let the finger in for rotating the filter. Quite insane if you ask me. My recommendation is to buy an after-market inexpensive lens hood of almost the same depth which can be screwed on to the filter. The filter can be screwed on to the lens. This arrangement apart from being giving clear access to the filter actually improves the usability. The filter can be easily rotated by grasping on the hood. Another small suggestion – always rotate these filters in the direction they are tightened on to the lens. This will prevent them from coming out loose and falling off accidentally.
Protection to front optical element
In the battle of UV filter users and non-users, the hoods also come up quite frequently. Photographers who tend to disagree with the use or clear filters for front element protection, recommend using lens hoods. These can prevent the front elements in case of accidental drops and from stray hands or any other objects from touching the front element. I am one of the few photographers who is not biased to any of the two. I use clear filter and lens hoods from time to time (and yes, sometimes both of them together) and the use depends on the situations where I am photographing. (Do read this – To use a clear filter or not?)
Barn-doors and Gobo (Not exactly lens hoods but a part of this discussion)
Another interesting way to prevent lens flare while using artificial light sources is to have some kind of hoods at the light source itself so that the stray light does not reach the lens. Barn-doors as the name says it are like doors of a barn or flaps attached to studio lights. These have to be opened up for using the light and are quite effective in preventing stray lights from entering the lens. These barn-doors are the ‘hoods’ for the light sources.
Gobo is a funny name for a very serious lighting aid. There is confusion as to where the term Gobo comes from. Some say it is the abbreviation for ‘GOes Before Optics’. Gobo help in focusing the light onto the subject. These again prevent any stray light from leaking out and causing flare.
Lens flare as a creative tool
Lens flare is not all that bad. It can add a feeling of depth, drama and even realism to a photograph. People’s minds are used to seeing lens flare and so it looks quite natural to look at when there are bright light sources in the frame. Lens flare when properly used can help control excess of contrast too while capturing the image. Photo-editing programs also provide option to add lens flare to the the photographs.
(Lens Flare seen as colored rings and circles in an almost straight line starting from the bright sun)
Though lens flare is not always bad, it is best to use a good lens hood most of the time. Even if there are no light sources visible in the frame or just outside the frame, the hood might just be preventing some amount of flare from a light source which you might not have noticed. And yes, they do provide protection too.