What Does "Fast SLR Camera Lenses" Mean?What does "fast SLR camera lenses" mean and how do you know if you have one?Are you considering a new lens but you're not sure what to look for? Knowing what fast SLR camera lenses are could be helpful in making the final decision. However, first of all and if you're not sure you may find it beneficial to visit the page
what does SLR stand for?
Among other things, you'll discover the connection between SLR cameras and the option to change lenses. Let's examine what is meant by fast SLR camera lenses.
Have you noticed the numbers on the lens?
They are giving you very helpful information.
Left, notice 52mm. Right notice both 1:3.5-5.6 and 18-55mm. The left image number does not refer to aperture. This is the physical diameter of the rim of the lens opening. For example, if you're buying a filter and the size of the rim of the lens opening is 52mm you will need a 52mm diameter size filter. About lens speed and what's meant by faster SLR camera lenses. Just to clarify, the term fast when applicable to a lens is not referring to capturing fast moving subjects. That's what shutter speed is about. When referring to a fast lens it relates to the maximum amount of light a lens can transmit. About these numbers on the lens. If you have a Single-Lens-Reflex camera your lens will have a set of numbers, too. They may be slightly different in range from this lens but that's okay. You'll find them somewhere. They may be on the side of the lens barrel or the edge of the lens rim. Sometimes it's challenging to find them and if you're really having trouble you may need to ask where you purchased the equipment. The numbers 1:3.5-5.6 on the lens refer to aperture, more specifically, the maximum aperture of the particular lens. Why is this helpful to know, what do the numbers mean and how do they relate to fast SLR camera lenses? Taking a look at the above example, the lens information reads 1:3.5-5.6. The number "1" is always listed first. It simply means, in camera language, "the maximum aperture of this lens is." For example if you have a lens which reads 1:2.8, your maximum aperture is f/2.8. In the photo above it reads 1:3.5-5.6. It also reads 18-55mm. This means that at 18mm, so no zoom and your widest angle, your maximum aperture is f/3.5. At 55mm, zooming to your longest focal length, your maximum aperture will be f/5.6. But I thought we were talking about fast SLR camera lenses so why all the mention of numbers on the lens?
As mentioned, a feature of a SLR camera is interchangeable lenses. Different lenses feature different aperture options, among other things. This can make quite a difference in certain situations. For now, let's look at the circles below the caption, size of opening in lens. Your camera actually has a diaphragm, comprised of a series of blades which form an opening in the middle. This diaphragm, or opening, is referred to as the aperture, as already mentioned a bit earlier. The circles, above, represent a few of the size of openings created by the diaphragm, openings you can change. What happens if you change the size of the opening? Light passes through this opening into the camera. As you adjust the size of the opening you are changing how much light passes into the camera. What about the numbers mentioned above? This is why knowing what these numbers mean is very helpful. Compare the circle f/2.8 to f/5.6. Do you see how there is more light passing through with f/2.8? The smaller the number the larger the opening which lets in more light. If you consider the lens with the example 1:3.5-5.6, this becomes quite significant. What this is telling you is, a lens with only the number f/2.8 will let in more light, always, while my lens zoomed to 55mm can only allow the amount relative to f/5.6. Let's pretend you're taking a drive and you've seen a photo opportunity but the light is beginning to fade. If you have both a 1:2.8 and the 1:3.5-5.6 which lens will allow more light to pass into the camera with focal, or zoom length, being the same? If you said 1:2.8 or the aperture f/2.8 you are absolutely correct! Why? Due to the smaller the number the greater the amount of light, just like in the examples shown of the circles. Therefore if both lenses, in the above going for a drive example, are appropriate for the subject the choice is the 1:2.8 or f/2.8 lens. This also means the 1:2:8 lens is a fast lens. Tying all of this together, a faster lens will be the f/2.8 as compared to f/5.6 because of the ability to admit more light. Therefore, a lens which admits more light than another is said to be the faster lens. For example, the f/1.4 lens will be faster than the f/2.8 which is faster than the f/3.5, which is faster than the f/5.6. Zoom lenses usually have a range, such as the example picture of the 1:3.5-5.6 with the 18-55mm lens. The numbers 3.5-5.6 are telling you the camera has two aperture capabilities. At 18mm, the widest view it has a lens speed of f/3.5. Change to zoom out to 55mm and now it has a lens speed of f/5.6. In comparison, let's say a 70-200mm lens reads 1:2.8. Now, no matter whether you're at your widest angle or zooming, the aperture will maintain at f/2.8. How we know this is because the lens has give us the information, hasn't it? Yes. It's important to know that with all other variables being equal and with two different lenses set to f/8, for example, both will let in exactly the same amount of light. A fast lens, so what? Again, this is the advantage linked to what does SLR stand for? Interchangeable lenses. The advantage is it allows you to photograph in lower light situations, which a slower lens cannot handle without compromising the shutter speed. Does this mean you need to go out and buy a faster lens? No. If you're shooting mostly in good lighting situations and not having a problem it's not necessary. There are other tools to
work with light requirements,
such as ISO and shutter speed.
A faster lens will not make you a better photographer just by owning it but it certainly is valuable depending on the reason for use. Visiting your local camera store will help you further understand fast SLR camera lenses, if necessary, as they can show you different lens models and which ones are faster. It's also possible they will show you the inside working of a SLR so you can visually relate to what does SLR stand for to the inner workings of the mirror and sensor. On a final note fast SLR camera lenses, like all camera gear, can be great fun plus help in capturing the desired end result.
It may cost a bit more and generally is heavier and longer so it's helpful to be aware of
camera shake.
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