All right, something else that you need to know about on lenses is that there is a place that you can shoot them to get the maximum sharpness from any particular lens. Now the general theory runs that lenses should be perfectly in every situation, even when they are shot wide open, and the reality is that they are not always totally sharp, there's imperfections and they are most easily seen when a lens is wide open, and so what the result of all this is, is that you need to stop your lens down, which means set it to four, five, six, F8, F in order to get the sharpest settings 'cause that starts disguising and hiding the imperfections that it had when it's wide open, but when you stop down too far, F11, 16, 22, 32, there's another problem that's called a diffraction, and this is caused by light scattering, passing through a very small aperture opening, as the light goes through that aperture it deflects, diffracts slightly and that light ends up someplace else on the sensor, which cause...
s a little bit of blurriness, it's not a lot, but it is a little blurry and so you'll find that shots taken with a very small aperture are not gonna be as sharp as ones taken with a larger aperture and so there is kind of a balance between one extreme and the other and so if you are just asking the question what is the best shutter speed, well let me give you some photographs to look at and we are gonna look at two cropped areas, one from the center and one from the corner of the frame and I want you to judge these photographs to see which are the sharpest set of photos. Probably the worst is the 1.4, this is where it shows the lens imperfections, but down at F22 it's not as sharp because of diffraction and so with any particular lens the sharpest area is gonna be towards the middle, now it's gonna vary from lens to lens, but if your lens is a 1.4 maximum aperture and it also goes down to 22, probably somewhere around five, six is the sharpest setting on the lens, it's not the most depth of field, depth of field and sharpness are two different issues, sharpness is how sharp is it in one particular area and if your lens goes to F4 as the maximum aperture, then probably something around F11. Now there are a lot of factors and we're gonna keep things a little bit on the simple side in this class and if you wanna go study up about this, you can do a little Wikipedia search for pixel size, airy disc and circle of confusion and you can dive in and find out more information about how sensor size and pixel size and how the viewing distance and the size of your images can effect where you might wanna be in shooting these sorts of things.
Once you’ve chosen the camera of your dreams, how do you know which lens will maximize your camera’s capabilities? Join camera expert John Greengo as he explains what the best lenses are to add to your camera bag. He’ll explain:
- Which lens is best for specific areas of photography
- The technology behind lenses
- How to use specialty lenses including macro and fisheye
- Tips on operating and maintaining your lenses
John will also talk about lens accessories including hoods, mounts, filters, and teleconverters. By the end of this class, you’ll understand exactly what lens you’ll need to take your best photos!