"full size" sensors?

[GraveyardMistress]

I've been reading through the forums trying to soak up as much as I can before I make an investment in a DSLR. One thing I've seen discussed a few times is moving up to a camera with a "full sized" sensor..... can someone clarify this for me? I would have thought most, if not all, DSLRs would have sensor better than a point and shoot, which are smaller, right?

Sorry if I sound lost :blush2:

[Frog]

I hope I can explain this..non technically.
I see you are accustomed to 35 mm. A full size sensor will have the same dimensions as a frame of 35mm film. Most sensors are smaller and this is why you hear about the crop factor being 1.6 on Canon and 1.5 on Nikon. Your images are more compressed.
Its also why a 50 mm lens becomes the same as a an 80 or 75 mm lens.
I'm sure the more technically savy can explain it better.
The full sensor cameras are pro models and cost more by the way. A lot more from what I've seen.

[Canuck935]

To add to that, the smaller DSLR sensors are still much, much, larger than what you'll get in any point and shoot camera. So yes, all DSLR's have waaaaaay better CCD/CMOS sensors than you'll find in a p&s.

[fx101]

I will put it simply. Like others have said, a full frame sensor has the proportions equal to that of a 35mm piece of film, that is, its the same size. However, most DSLR's don't have this size because of the added expense of producing a larger sensor.

Thus, most SLR's use what is called the APS format. Basically, the sensor is equal to the size of APS film (an obsolete format BTW) which is smaller than 35mm film but still WAAAY larger than the pencil tip sized sensors in Point and Shoot cameras.

Now here's the thing. Let's say you have a full frame SLR and an APS sensor SLR, say the Nikon D80. Let's say you mount a 12-24mm lens on both. You take pictures with both. You will notice the pictures on the full frame SLR will have a wider angle than those of the Nikon D80. This is because APS sized (anything smaller than 35mm) will experience a crop factor due to the smaller sensor, of something about 1.4. Let's make it 1.5 for the sake of math. For the full frame SLR the lens will behave as usual. But for the D80, the lens is actually 12(1.5)-24(1.5)=18-36mm. Notice it is a different focal range.

So why bother with a full frame? For landscape photographers, getting those extra millimeters matter. Also, larger sensors can have larger resolutions. Also, larger sensors sometimes mean a larger pentaprism (what reflects light up to the viewfinder) resulting in a 100% coverage viewfinder and a brighter viewfinder too. For your first DSLR don't bother. Because these cameras will be heavier, much more expensive, and not nescessarily will provide better image quality.

[Franglais]

When people talk about "Full Size" or "Full frame" they are talking about using a camera system originally designed for 24x36mm film format with a digital sensor that is also 24x36mm format. When they say "Crop" format this means that the sensor format is smaller than 24x36, so the sensor is only taking in a part of the image (which is actually a circle - even a 24x36 film frame is only taking part of it).

The view given by a lens depends on it's focal length, expressed in millimetres. The more the number of millimeters, the more like a telescope the lens is. People have become accustomed to talking about lenses in terms of millimetres which correspond to a certain view when used on a piece of 24x36 film:

28mm = wide-angle
50mm = normal
105mm = mild telephoto
300mm = long telephoto

When you use a smaller sensor then you are effectively cropping off the edges of the image. The result is that you get an image which is more telephoto. In order to know what is the equivalent view in 24x36 terms with a given lens on a given sensor you multiply by the correction factor. Most DSLR's use the APS-C sensor size which has a correction factor of 1.5. So a 28mm becomes the equivalent of a 28x1.5=42mm which makes it a sort of "normal" lens rather than a "wide-angle".

The correction factor has no effect on picture-taking. You just put the lens on the camera, look through the viewfinder and fire away.

The advantages of using a "crop" sensor:

- much MUCH cheaper to produce than a larger sensor
- only uses the central part of the image made by the lens so no problems with loss of quality and light fall-off at the edges
- allows smaller and lighter cameras and lenses

The advantages of using a "full frame" sensor:

- the sensor is physically bigger so it can capture more light. This means a better compromise between image quality and sensitivity
- people can carry on using their lenses just the same as they did with film

Personally I think the whole thing is silly. It's the results that count.

[DEvianT]

As a side note there are advantages to a full frame sensor if you are biased towards certain kinds of photography and disadvantages if you lean towards others.

You get a shallower depth of field with a full frame sensor which is great in weddings and portraits. It isolates subjects well from their backgrounds.

You get better signal to noise on the sensor so the images are less noisy.

Disadvantages are that you loose 'reach' on your lenses your 200mm telephoto does not crop to look like a 320mm lens. If you shoot sports or wildlife you may actually WANT a crop camera.

[readingr]

Disadvantages are that you loose 'reach' on your lenses your 200mm telephoto does not crop to look like a 320mm lens. If you shoot sports or wildlife you may actually WANT a crop camera.

Let's not forget that this is not extra magnification just a different crop which you can achieve using photoshop.

Roger

[DEvianT]

Quite correct magnification of any given optic won't change due to sensor size it just crops as you said. However doing a crop that drastic in photoshop looses you tons of megapixels.

[Jumpseat]

Ken Rockwell has just published an excellent article concerning the image diffences between Full frame and APS size sensors titled, "The Full Frame Advantage." It can be found at: http://www.kenrockwell.com/tech/full...-advantage.htm

[jmfraz]

Sorry if this is a stupid question, I am a beginner. Is what I see through my viewfinder what I get or is that the full image that has yet to be cropped?

[mjs1973]

Welcome to the Forum jmfraz. For the most part, what you see is what you get when looking through the view finder of a DSLR. The rub is, that not all view finders on all DSLR's are the same. Some will show you 100%, other will show you a little less. So to answer your questions, the image you see in your view finder, is already "cropped", BUT it may be cropped a little more than what you will actually get. What this means is, that you may actually get a little wider view on your photo than what you saw in your view finder.

I hope I didn't confuse you. If you have more questions, let us know.