1. A camera lens (also known as photographic lens, objective lens or photographic objective) is
an optical lens or assembly of lenses used in conjunction with a camera body and
mechanism to make images of objects either on photographic film or on other media
capable of storing an image chemically or electronically.
While in principle a simple convex lens will suffice, in practice a compound lens made up of a
number of optical lens elements is required to correct (as much as possible) the many
optical aberrations that arise. Some aberrations will be present in any lens system. It is the
job of the lens designer to balance these out and produce a design that is suitable for
photographic use and possibly mass production.
There is no major difference in principle between a lenses used for a still camera, a video
camera, a telescope, a microscope, or other apparatus, but the detailed design and
construction are different.
A lens may be permanently fixed to a camera, or it may be interchangeable with lenses of
different focal lengths, apertures, and other properties.
At first glance, digital photography would seem not to affect lenses, since it is a camera
technology for the capture and storage, but not the creation, of images. However, electronic
image processing provides an opportunity to improve lens images far beyond a simple
contrast boosting Unsharp Mask.
In 2004, the Kodak (Sigma) DSC Pro SLR/c (USA/Japan) digital SLR was loaded with optical
performance profiles on 110 lenses so that the on-board computer could correct the lateral
chromatic aberration of those lenses, on-the-fly as part of the capture process. Also in 2004,
DO Labs DoX Optics Pro (France) computer software modules were introduced, loaded with
information on specific cameras and lenses, that could correct distortion, vignetting, blur
and lateral chromatic aberration of images in post-production.
Lenses have already appeared whose image quality would have been marginal or
unacceptable in the film era, but are acceptable in the digital era because the cameras for
which they are intended automatically correct their defects. For example, onboard
automatic software image correction is a standard feature of 2008's Micro Four Thirds digital
format. Images from the 2009 Panasonic 14-140mm f/4-5.8 G VARIO ASPH. MEGA O.I.S. and
the 2010 Olympus M. Zuiko Digital 14-150mm f/4-5.6 ED lenses (both Japan) have their
severe barrel distortion at the wide angle settings automatically reduced by a Panasonic
LUMIX DMC-GH1 and Olympus Pen E-P2, respectively. The Panasonic 14-140mm lens also
has its chromatic aberration corrected. (Olympus has not yet implemented chromatic
aberration correction.)
In photography, a lens hood or lens shade is a device used on the end of a lens to block the
sun or other light source in order to prevent glare and lens flare.
The geometry of the lens hood can vary from a plain cylindrical or conical section (much like
a lamp shade) to a more complex cut sometimes called a petal, tulip or flower hood (as
shown in some of the pictures), which produce a reasonable good shade without blocking
the field of view of the lens and thus producing vignetting. Properly petal shaped lens hoods

2. produce more shade than normal lens hoods with the same end diameter. Square lens
hoods may be even better.
Lens hoods are more prominent in long focus lenses because the field of view has a smaller
viewing angle than of wide-angle lenses. For wide angle lenses, the length of the hood (away
from the end of the lens) cannot be as long as those for telephoto lenses because of the
viewing angle.
Lens hoods are often designed to fit onto the matching lens facing either forward, for
normal use, or backwards, so that the hood may be stored with the lens without occupying
much additional space. Some lens hoods are flexible and collapse for storage.
In addition, they offer some physical protection for the lens due to the hood extending
farther than the lens itself.
In photography and videography, a filter is a camera accessory consisting of an optical filter
that can be inserted in the optical path. The filter can be a square or oblong shape mounted
in a holder accessory, or, more commonly, a glass or plastic disk with a metal or plastic ring
frame, which can be screwed in front of or clipped onto the lens.
Filters modify the images recorded. Sometimes they are used to make only subtle changes
to images; other times the image would simply not be possible without them. In
monochrome photography coloured filters affect the relative brightness of different colours;
red lipstick may be rendered as anything from almost white to almost black with different
filters. Others change the colour balance of images, so that photographs under incandescent
lighting show colours as they are perceived, rather than with a reddish tinge. There are
filters that distort the image in a desired way, diffusing an otherwise sharp image, adding a
starry effect, etc. Supplementary close-up lenses may be classified as filters. Linear and
circular polarizing filters reduce oblique reflections from non-metallic surfaces.
Many filters absorb part of the light available, necessitating longer exposure. As the filter is
in the optical path, any imperfections—non-flat or non-parallel surfaces, reflections
(minimized by optical coating), scratches, dirt—affect the image.
There is no universal standard naming system for filters. The Written numbers adopted in
the early twentieth century by Kodak, then a dominant force in film photography, are used
by several manufacturers. Colour correction filters are often identified by a code of the form
CC50Y—CC for colour correction, 50 for the strength of the filter, Y for yellow.
Optical filters are used in various areas of science, including in particular astronomy; they
are essentially the same as photographic filters, but in practice often need far more
accurately-controlled optical properties and precisely-defined transmission curves than
filters exclusively for photographic use. Photographic filters sell in larger quantities at
correspondingly lower prices than many laboratory filters. The article on optical filters has
material relevant to photographic filters.

3. There are a wide variety of digital SLR camera cases for you to choose from.
Camera cases come in all shapes and sizes, from the simple form-fitted case to a backpack
with pouches galore.
So how do you select the right one?
It comes down to one important question: how much gear do you need to take the photos
you love?
The Case for a Case
If you've just spent 500+ dollars (or any significant amount of currency) on a digital SLR it
makes sense to protect it.
Here's the thing: digital SLR cameras are accident-prone.
Most compact cameras can take a beating. The lens is enclosed in the camera body when
not used, and the camera doesn't have a lot of joints where water and sand can sneak in.
Digital SLR cameras have lots of openings: one for the lens, one for the battery, and one for
the memory card...the list goes on.
Each one of these opening presents an opportunity (although slight) for your camera's
electronics to get affected by wind and weather.
It doesn't help that SLR lenses extend from the camera body at all times, and are easy to
bang and scrape on rocks and other sharp objects.
Digital SLR camera cases are designed to prevent these kinds of mishaps.
Types of Cases:
There are 3 basic types of digital SLR camera cases for the average photographer:
Form-fitting cases
Small bags and camera packs
Backpacks and sling packs
Form-fitting digital SLR camera cases are designed for specific cameras.
Since they are designed to fit snugly around the camera body, you can't use them with
cameras that have different shapes. They aren't one-size-fits-all solutions.
Small bags and fanny packs are best suited for one camera with several lenses. They're
versatile: these digital SLR camera cases can carry a variety of camera models.
They are great for hiking trips and other times where you don't need to pack a lot of gear,
but want your camera along for the ride.

4. Backpacks and sling packs are for photographers who want to carry lots of gear all the time.
They're designed for longer trips (not day hikes) when you're not sure exactly what type of
photo opportunity might present itself.
Which One to Get?
Now I'll get back to that question about digital SLR camera cases.
How much gear do you really want?
One Camera and Lens
A form-fitting digital SLR camera case is a good option if you don't think you'll ever use more
than the camera and lens that you purchased.
If the camera and lens takes the photos you love, then get a case that fits it well. This will
keep it covered and protected when not in use.
The only trick is finding the right case for your camera: here's a list of digital SLR camera
cases fitted for specific camera models.
One Camera plus Extras
If you think that you might branch out in the future and get an extra lens or a flash for your
camera, the form-fitting case won't work.
Instead, opt for a small bag that has enough room for your camera plus a few accessories.
A camera case like this gives you some room to grow so that you can explore more styles of
photography in the future.
Sky's the Limit
For all of you with impulse-control issues (like me) a backpack or sling pack is probably a
good idea.
I started out with one camera and one lens.
Today I have 2 camera bodies, 4 lenses, three external flashes, a tripod, filters...you get the
picture.
The nice part about having a digital SLR camera case large enough to store all of this gear is
that it's all in one place.
If I have to run out the door quickly to take some photos I can do it without worrying about
where I've put all of my camera gear.
Recommendation:
The only digital SLR camera case that I can personally recommend is one that I have used
extensively: the Adorama Slinger Bag.

5. This bag is definitely for anyone with a lot of gear (or who expects to have a lot).
Here are some of the reasons why I chose it:
Main compartment closes off with a clip instead of a zipper, allowing quick access to the
inside
Includes both shoulder strap and waist strap and is quite comfortable when carrying 10
pounds of gear
Plenty of pockets allow me to carry extra memory cards, batteries and other small
accessories
All my stuff fits into one bag - great for travel, when I want to keep everything with me
For the style conscious, it comes in Black, Green, Gray, Maroon, Navy and Camouflage