What's the difference in full frame and CMOS

Discussion in 'Beginner Questions' started by ron_brown|6, Dec 10, 2011.

  1. I was wondering if someone could please explain to me what the difference is between a full frame sensor and a small sensor, or crop sensor. Or perhaps guide me to a website showing some side by side examples of images.
    I don't understand if it has something to do with showing more in the finished image, is it a preferred professionals choice to shoot full frame.
    I shoot with a Canon 400D, which is a small sensor, so I wonder if I am getting everything I should be with a small frame camera. Of course to upgrade to a full frame Canon is quite expensive, as first in line is the 5D. Any help explaining the difference would be very appreciated. Thanks everyone, Ron
  2. I'm sure there are seasoned pro's who will answer this better then I … but here goes ..
    before you drive yourself crazy .. STOP and repeat after me .. "Full frame is not better .. it's just different"
    .. that said, most people use full frame for portraits and wide angle .. and a crops for tele's and macro .. a 50mm on your crop - will be similar to an 85 on a full frame (similar but not the same) .. it's more about how you attack the subject and than how the camera interprets it ..
  3. "Full frame" is a description of sensor size, sort of...
    "CMOS" is a name for semiconductor technology used to make sensors.
    So, they are definitely different, and not comparable. E.g. like shoes and gloves.
    Search "Crop factor" in the search window, and you will find tons of explanations.
    E.g. one is:
    Though, there is a lot of confusion about the crop factor, but by reading a lot, you will come to the most likely good understanding.
  4. First, notice that your 400D only has 10.1 mp, but the image quality is much better than the 12,1 mp PowerShot A3100. The main reason is sensor size (or actually pixel size). However the sensor size difference between 5D and 400D is not that much and how much is this difference? is it different enough for you to upgrade your camera? That depends on you. Maybe you should try it out and judge it yourself.
    The higher level cameras also have more and better features. These features may be very important to some people but again are they important enough to you? For example, I really care for "the big wheel in the back", prism viewfinder, which your 400D don't have
    I know may professionals who used 400D and are using 60D now, or other cropped sensor cameras and they make good money. Besides, IMHO, being professional only means they can deliver what their customers expect
  5. The info in this link might be helpful:
  6. just for the record
    The poster (here and elsewhere) seems to be confusing CMOS and APS-C.
    As said, one is a sensor type, the other is an old film format now used to describe sensor sizes that are similar.
  7. The APC-C is roughly the same size as the 'half-frame 35mm' or 35mm motion picture frame. Full frame digital is the same size as what 35mm film is ... you may or not need it depending on what you do.
    For a diagram of the different sizes check out www,dpreview.com
  8. "Full frame" refers to the sensor size being the same (approximately) as a 35mm film frame, or 24mm x 36mm. "Crop Sensor" cameras have a sensor that is smaller than 24mmx36mm. Your 400D has a sensor 14.8mmx22.2mm, and is often called "APS-C", in reference to a similar frame size available with the (nearly, if not completely, defunct) APS film cameras.(Wikipedia article on Image Sensor Formats)
    One is not necessarily better than the other. There are pros and cons to each, many of which depend on your particular application. Pro photographers use either, or often both, depending on the situation.
    A big difference between the two sensor sizes is their apparent effect on lenses. Note that I said apparent. The lens itself never changes, but the image the sensor sees does. For a quick and dirty example of the effect, hold your hands straight out front of you, with the tips of your thumbs touching, in the classic "movie director" pose, as though you were framing a shot for a film. Look at a scene (out the window, another corner of the room, at your children, whatever), and make careful note of what you see in that scene around the edges. We'll call this view "full frame". After you note all that, overlap your thumbs so the tip of one is touching the second knuckle of the other. You'll see that the view is narrower, and some of the scene is cropped off at the sides. We'll call this view "crop frame". That's all there is to it as far as the physical size goes.
    Now, what that affects on a lens is the scene you see. Let's say you want to take a photo of five people standing shoulder-to-shoulder. If you start with a full-frame sensor, and a lens of X focal length, you get all five in the shot, out to the edges. If you changed to a crop-frame camera, used the same lens, and did not move, you would only be able to get the center three people, and perhaps a bit of the others in the frame. Your choices to get all of them in are to get a wider lens (smaller # in mm), or to move back from your subjects until you get them all in again.
    Now, that might be considered a "bad" thing for crop sensors. However, this same effect has distinct advantages when we go to photographing things farther away, like wildlife, or sports. The crop sensor "sees" a narrower part of the scene. Essentially, that is what you are doing when you mount a longer focal length lens on your camera (with a little bit of magnification, too...). So, your long lens becomes effectively longer. And that can be very important when you're shopping for those 500mm and up lenses that cost as much as a good used car! A good example of this in action would be wildlife shooting. A 500mm lens (list price of $7,000) on a crop camera (like your 400D) "sees" the same scene as a full-frame camera does using an 800mm lens (list price of $14,000!)!
    Oh, before you get bogged down in figuring out your effective focal lengths, believe me, it just isn't that important, unless you happen to have both sensor sizes on cameras that you own! I have a Canon 7D, same size sensor as the 400D, and while someplace in the back of my head, I "know" that my 100-400 L zoom is "effectively" 160mm to 640mm when on my 7D, I never think of it like that. I just know I want a 500 with a 1.4 converter, giving me the option for a 700mm focal length! (but my sensor "sees" like it's an 1,120mm!)
    To be sure, there are many reasons besides sensor size to buy full-frame sensor cameras. They often are the flagships of their line, and as such, get the more advanced features long before they filter down to the cheaper cameras.
    The bottom line is, both sensor sizes can take great photos. The best way to do that is to learn the camera that you have, use it often, buy good lenses, and have fun!

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