b0314w said:
can find almost anywhere - CP, AP, Ms etc...
Lens hood
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can find almost anywhere - CP, AP, Ms etc...
This is an article from Bob Johnson. Sorry I cannot find the URL anymore but I did copy i down to read in my leisure hours.
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Giving Lens Hoods Their Due
by Bob Johnson
Apart from cameras themselves, lenses get all the glory in the world of photography. Most photographers have several lenses, but always seem to want more. When new lenses are released, people lust over them. Some dedicated individuals devote a great deal of effort to reviewing lenses. A few people even collect lenses much as one would baseball cards. Really expensive baseball cards.
Lens hoods on the other hand get very little attention. Many photographers don't even bother with them, viewing them as nuisances that occupy space in their bag. Many photographers would rather use the space for other things. Like more lenses I suppose. Others know they ought to use lens hoods, but generally don't. Many people never bother with lens hoods unless they're shooting into the sun, figuring that they otherwise don't really need them. After all, lenses seem to take pictures just fine without lens hoods, so what is all the hype about?
Photo copyright Bob Johnson
For starters, lens hoods will help prevent lens flare, something you probably already knew even if you didn't have a full appreciation of that fact. If stray light from the sun or any other bright light source hits the front element of a lens at an angle, it can reflect off the interior glass surfaces. This creates color artifacts and other ghosting in the image. Zoom lenses are convenient but tend to have more flare potential than prime lenses since they have more glass/air interfaces to reflect stray light. Multi-coatings (prevalent on modern lenses) do wonders to help minimize flare, but the problem can't be totally controlled by lens coatings alone.
A lens hood works to block the root cause of flare by preventing stray light from ever reaching the front of your lens. No lens hood can block all chance of flare. If the sun or other light source is actually visible in your image, the hood couldn't block it without interfering with the image itself.
Yet lens hoods do more than just prevent flare. They will also help improve contrast, even when the sun is behind you.
The way we see is based on light, which is obvious enough if you've ever dropped your car keys in a dark parking lot. Get out a flash light, and finding them can become a simple problem. If you don't have a flashlight though, you're in for a fun time feeling around on the pavement. Not that I've ever done this of course.
Of those things we can see, some actually radiate light like the sun or that flashlight in the parking lot. But most things only reflect it. When light strikes an object, some wavelengths are absorbed and others are reflected which determines an object's color. If something appears to be red, it reflects red light and absorbs other colors. If it's green, everything except green is absorbed and we see the reflected green wavelengths. Only black objects absorb all wavelengths, while objects that appear white reflect all colors evenly.
Unlike direct reflections and glare from shiny objects, most reflections are diffuse and appear much the same brightness and color no matter what direction we view them from. This is why something that is red or green stays red or green no matter what direction we view it from. As we walk around an object relative to the light source that is illuminating it, its color remains more or less the same. this is how we know it is reflecting light in all directions. It manifests that color inspite of our movement.
Stop for a moment then and look at everything that is around you right now. If you can see it, it is reflecting light back to you in the wavelength corresponding to its color. Now pick up a camera and point it at something of interest. You will narrow your view and crop out most of the stuff you originally saw. If you are not using a lens hood though, even things you can't see in the viewfinder are still reflecting some light on the front element of your lens.
While this light is likely not bright enough to cause visible flare, the sum total from all sources is sufficient to produce a kind of "visual white noise" that will lessen the contrast of what you are trying to photograph. It creates a floor below which your blacks can't go. A well-fitting lens hood will shield your lens in all directions. This way, things that don't directly contribute to the image are blocked. This reduces the background "noise" or light that reflects from everything you are not photographing.
Illustration copyright Bob Johnson
A hood can also provide one of the best ways to protect your lens from peril. Some people advocate the use of a skylight or UV filter for protection, but it seems to me that a lens hood is more practical.
Fingerprints and general grime your problem? A lens hood will keep your fingers away from the lens, whereas a UV filter only gives you something different to get dirty. You still have to shoot through the grime. Afraid you're going to hit the front of your lens with a tree branch or other obstacle? A lens hood will help keep things away just as it does your fingers. The hood is cheaper to replace than the lens.
How about the possibility that your lens will get dropped? Hopefully it won't happen, but someday it might. If it does, much of the energy will be dissipated into the ground, but enough can be left over to possibly do damage. There's an almost religious war on some internet discussion lists as to whether a filter or a hood offers better protection for falls. I'm not here to change anyone's mind. This is probably an opportunity for someone to do their doctoral thesis, but my money is on the lens hood. Both a filter and a hood could easily break if affixed to a dropped lens, but the hood will keep the impact further away from what matters. It is also more likely to absorb energy from the impact. I've heard stories of lenses with filters dropping that resulted in the filter breaking. The theory then is that the owners would rather have the filter break than the front element. But the glass in a filter averages only one to three millimeters in thickness. It would break more easily than the thicker elements used in lens construction. In these cases, the front element would be less likely to break anyway.
When not in use, of course, putting a lens cap on and placing the lens in your bag is your best bet for protection.
Some lenses come with lens hoods, but many don't. This causes people to avoid hoods solely in the interest of saving money. Don't be tempted. Each lens should have a hood for it, preferably the one designed for it by the lens manufacturer. A purpose-built hood will almost certainly offer better protection than an aftermarket hood that doesn't match the angle of view of the lens.
Lens hoods can be metal, rubber, plastic or other hybrid materials. Metal hoods seem like the most durable but can become dented or dinged through use. Rubber hoods can't get dinged, but do get malformed if not taken care of. There's nothing worse than a hood that is supposed to fit well but isn't even round anymore. These days, the majority of hoods are made from various high-tech plastic compounds. This makes them lightweight and fairly impervious to damage in regular use. Lens hoods come in different shapes too. Due to the narrower angle of view, those for telephoto lenses can be manufactured to stick out further than those for wide angles. Many hoods have started coming in interesting petal designs to match the shape of 35mm film which is wider than it is tall.
So, the moral of this little tale is: Give the lowly lens hood its proper due. ALWAYS use the right hood for your lens, even when there's no "obvious" reason for doing so.
-------------------------------------
Article by Bob Johnson, anyone who know the url can post it here and i will remove this post.
------------------------------------------------------------------------------
Giving Lens Hoods Their Due
by Bob Johnson
Apart from cameras themselves, lenses get all the glory in the world of photography. Most photographers have several lenses, but always seem to want more. When new lenses are released, people lust over them. Some dedicated individuals devote a great deal of effort to reviewing lenses. A few people even collect lenses much as one would baseball cards. Really expensive baseball cards.
Lens hoods on the other hand get very little attention. Many photographers don't even bother with them, viewing them as nuisances that occupy space in their bag. Many photographers would rather use the space for other things. Like more lenses I suppose. Others know they ought to use lens hoods, but generally don't. Many people never bother with lens hoods unless they're shooting into the sun, figuring that they otherwise don't really need them. After all, lenses seem to take pictures just fine without lens hoods, so what is all the hype about?
Photo copyright Bob Johnson
For starters, lens hoods will help prevent lens flare, something you probably already knew even if you didn't have a full appreciation of that fact. If stray light from the sun or any other bright light source hits the front element of a lens at an angle, it can reflect off the interior glass surfaces. This creates color artifacts and other ghosting in the image. Zoom lenses are convenient but tend to have more flare potential than prime lenses since they have more glass/air interfaces to reflect stray light. Multi-coatings (prevalent on modern lenses) do wonders to help minimize flare, but the problem can't be totally controlled by lens coatings alone.
A lens hood works to block the root cause of flare by preventing stray light from ever reaching the front of your lens. No lens hood can block all chance of flare. If the sun or other light source is actually visible in your image, the hood couldn't block it without interfering with the image itself.
Yet lens hoods do more than just prevent flare. They will also help improve contrast, even when the sun is behind you.
The way we see is based on light, which is obvious enough if you've ever dropped your car keys in a dark parking lot. Get out a flash light, and finding them can become a simple problem. If you don't have a flashlight though, you're in for a fun time feeling around on the pavement. Not that I've ever done this of course.
Of those things we can see, some actually radiate light like the sun or that flashlight in the parking lot. But most things only reflect it. When light strikes an object, some wavelengths are absorbed and others are reflected which determines an object's color. If something appears to be red, it reflects red light and absorbs other colors. If it's green, everything except green is absorbed and we see the reflected green wavelengths. Only black objects absorb all wavelengths, while objects that appear white reflect all colors evenly.
Unlike direct reflections and glare from shiny objects, most reflections are diffuse and appear much the same brightness and color no matter what direction we view them from. This is why something that is red or green stays red or green no matter what direction we view it from. As we walk around an object relative to the light source that is illuminating it, its color remains more or less the same. this is how we know it is reflecting light in all directions. It manifests that color inspite of our movement.
Stop for a moment then and look at everything that is around you right now. If you can see it, it is reflecting light back to you in the wavelength corresponding to its color. Now pick up a camera and point it at something of interest. You will narrow your view and crop out most of the stuff you originally saw. If you are not using a lens hood though, even things you can't see in the viewfinder are still reflecting some light on the front element of your lens.
While this light is likely not bright enough to cause visible flare, the sum total from all sources is sufficient to produce a kind of "visual white noise" that will lessen the contrast of what you are trying to photograph. It creates a floor below which your blacks can't go. A well-fitting lens hood will shield your lens in all directions. This way, things that don't directly contribute to the image are blocked. This reduces the background "noise" or light that reflects from everything you are not photographing.
Illustration copyright Bob Johnson
A hood can also provide one of the best ways to protect your lens from peril. Some people advocate the use of a skylight or UV filter for protection, but it seems to me that a lens hood is more practical.
Fingerprints and general grime your problem? A lens hood will keep your fingers away from the lens, whereas a UV filter only gives you something different to get dirty. You still have to shoot through the grime. Afraid you're going to hit the front of your lens with a tree branch or other obstacle? A lens hood will help keep things away just as it does your fingers. The hood is cheaper to replace than the lens.
How about the possibility that your lens will get dropped? Hopefully it won't happen, but someday it might. If it does, much of the energy will be dissipated into the ground, but enough can be left over to possibly do damage. There's an almost religious war on some internet discussion lists as to whether a filter or a hood offers better protection for falls. I'm not here to change anyone's mind. This is probably an opportunity for someone to do their doctoral thesis, but my money is on the lens hood. Both a filter and a hood could easily break if affixed to a dropped lens, but the hood will keep the impact further away from what matters. It is also more likely to absorb energy from the impact. I've heard stories of lenses with filters dropping that resulted in the filter breaking. The theory then is that the owners would rather have the filter break than the front element. But the glass in a filter averages only one to three millimeters in thickness. It would break more easily than the thicker elements used in lens construction. In these cases, the front element would be less likely to break anyway.
When not in use, of course, putting a lens cap on and placing the lens in your bag is your best bet for protection.
Some lenses come with lens hoods, but many don't. This causes people to avoid hoods solely in the interest of saving money. Don't be tempted. Each lens should have a hood for it, preferably the one designed for it by the lens manufacturer. A purpose-built hood will almost certainly offer better protection than an aftermarket hood that doesn't match the angle of view of the lens.
Lens hoods can be metal, rubber, plastic or other hybrid materials. Metal hoods seem like the most durable but can become dented or dinged through use. Rubber hoods can't get dinged, but do get malformed if not taken care of. There's nothing worse than a hood that is supposed to fit well but isn't even round anymore. These days, the majority of hoods are made from various high-tech plastic compounds. This makes them lightweight and fairly impervious to damage in regular use. Lens hoods come in different shapes too. Due to the narrower angle of view, those for telephoto lenses can be manufactured to stick out further than those for wide angles. Many hoods have started coming in interesting petal designs to match the shape of 35mm film which is wider than it is tall.
So, the moral of this little tale is: Give the lowly lens hood its proper due. ALWAYS use the right hood for your lens, even when there's no "obvious" reason for doing so.
-------------------------------------
Article by Bob Johnson, anyone who know the url can post it here and i will remove this post.
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