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Hi everyone,


I'm just a little bit uncertain about the differences between a full frame DSLR and a cropped one; what's the difference? I have a Canon Rebel T2i, and as far as I know its cropped, but I don't really know what that means and/or what advantages a full frame sensor has over one. And how does that affect a decision in buying lenses?



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A full frame DSLR has a sensor that is 36mm x 24mm where as a cropped DSLR has a sensor that is smaller than 36mm x 24mm.

Nikon DSLRs have a crop factor of 1.5

Canon DSLRs have a crop factor of 1.3 and 1.6, depending on the model.


One advantage of using a cropped sensor is the crop factor.

Let's say you have a crop factor of 1.5 and you are using a 50mm lens, the 35mm or full frame equivalent would be 75mm; Crop Factor * Focal Length.

Basically, you get a "focal length boost" when you use a cropped sensor DSLR.

This really helps out when you are using telephoto lenses.


The advantage of using a full frame sensor is if you use a 50mm lens, it's a 50mm lens.

The pixel sites on a full frame sensor are usually larger then on a cropped sensor.


Full frame lenses are usually more expensive than a cropped sensor lens.

If you are planning to get a Canon with a Full Frame sensor in the future, you may want to invest in full frame glass.

This is not to say you can't use a cropped sensor lens on a Full Frame DSLR, but you will not be using entire sensor.


Hope this helps,

Paul K

That helps a ton, thank you! So is it better to opt for a full frame lens right now even if I have a cropped sensor? I definitely want to get a full frame in the future, but I checked and my t2i is a 1.6. Thanks for your help!

You are correct, your Rebel T2i has a crop sensor.  It is about half the size of a full frame sensor.  But the sensor in the T2i is quite good and produces excellent photos.  Having a crop sensor camera means you can use EF-S lenses and similar lenses from other manufacturers.  Some of those lenses have a piece that fits into the camera body and interferes with the mirror on a full frame camera.  They also have a smaller image circle so on a full frame sensor you get a dark circle around the image.  The benefits include much less weight.  A full frame body has to accommodate a larger mirror so the whole body is larger and heavier.  Since they are made for different markets, they are also usually a bit more robust.


Some crop sensors just crop, others provide a bit of a zoom effect, it depends on the density of pixels on the sensor.  The  Rebel T2i has enough pixels that the effect is to increase the focal length.  A camera like the 30D has the same size sensor but less pixels so the effect is simply to crop (the angle of view is smaller).  Everything else being equal, more pixels on a sensor mean smaller pixels and smaller pixels generally have a poorer signal to noise ratio than larger pixels.  They may also have more trouble with contrast.  The latest versions of sensor and software deal with this pretty well so the Rebel T2i and the 7D can take excellent shots in low light even with the crop sensor.


Sometimes a picture is worth a thousand words, so here are some pictures:


These were taken through the white lens in the last picture, at 300 mm.  4 second shutter, mirror locked up, aperture at f/5.6, ISO 200 auto white balance, shot in raw mode and processed with Photoshop CS5 with default settings then reduced and converted to sRGB.  They were taken a couple of minutes apart, just enough time to change bodies and confirm settings.

This is from a Rebel T2i:


This was taken with a 1Ds Mk III:


This is a 100% crop from the Rebel T2i:


This is a 100% crop from the 1Ds Mk III:


The lens on the left is a SIGMA 18-250mm F3.5-6.3 DC OS HSM, the one on the right is a CANON EF 28-300MM F3.5-5.6 L IS USM, as you can see, much larger with a larger rear element.  Also, much heavier and more expensive.  Converted using the crop factor, the smaller lens is said to be the 35 mm equivalent of 28.8 - 400 mm.


Also note the noise difference between the two...good examples. In my opinion that is quite a bit of difference. Especially when you hit the higher iso's.

Those people above are a lot experienced than me. So, I just want to have an opinion on my understanding.


As I understand it, when you say crop, you are cutting. So, a crop factor is a cut.

so, if a full frame lens attached to a full frame body you get the whole picture. But, when you attach the full frame lens on the APS-C body, the picture is just cut because the sensor cannot see the entire image because it is smaller. My idea, is that, considering that everything is the same except for the body. Both bodies gets the same quality of image, only that the APS-C body has a cut image. So, if you cut the image taken from a full frame so that the cropping will look the same to that with the one taken with an APS-C body, the pixelation is the same.


What I mean is that, attaching a full frame lens on the APS-C body does not really multiply the focal length, because you are not getting an improve image after all. What you are just seeing is false assumption of a multiplier.






Here's another way to look at this.

I believe you have Nikon, so this has a crop factor of 1.5.

If you take a picture with your camera and a 50mm lens and I wanted to get the same exact image, I would need to put a 75mm lens on my full frame camera.


If I took the same picture with a 50mm lens on a full frame camera, I would see more of the scene.


Here is a way to simulate the crop factor with your Nikon.

I don't know what lenses you have, but let’s say you have an 18-200mm Telephoto.

Take a picture at 18mm, this will represent the Full Frame Image.

Now take a picture at 27mm, this will represent the Crop Factor Image (18 x 1.5 = 27)

Now compare the two images, notice how the 18mm has more of the scene than the 27mm image.

This is how the crop factor works.


Hope this makes sense...


Paul K 

I get that idea, but I am actually thinking about the quality of the image. I could be wrong, because I just thought that pixelation occurs in the sensor. But, maybe someone with both an APS-C body and a full frame body can do the favor of making an example.


My idea is to shot both image with the same everything except for the body. Then, crop the full frame image, in an image editing software, so that it is cropped like the image from the APS-C body.


I have a Nikon D5000 + Sigma 70-300mm DG Macro (no OS no APO).

Vernan, look at the examples above, they were taken with a Canon Rebel T2i, 18 Mpx. Crop factor 1.6 and a Canon 1Ds Mk III full frame 21.5 Mpx, Crop factor 1.  It shows the result of putting 2 different bodies on the same lens, at the same focal length, with the same ISO, aperture and shutter speed.  You would get very similar results if you did the same thing with Nikon equipment.


Here is an example of the image from a Canon 30D overlaid on the image from a 1Ds Mk III:

Thats a good visual display of the cropped sensor,

another way of looking at the DX format (Nikon) is as a very high quality tele-converter :-)

No, there is no teleconverter function going on.  Having a smaller sensor does not change the focal length of the lens.  Crop is the correct word because relative to a full frame, that is what is happening.  Because the sensor is smaller, you get a smaller field of view.  If you look at a picture from a crop sensor camera and from a full frame camera, it appears the focal length has changed, but if the pixel density on the sensors is the same, then viewing a part of the image at 100%, you will see the focal length is unchanged.

Some crop sensors have a higher number of smaller pixels per unit of surface area on the sensor than some full frame sensors.  The larger pixels on the full frame sensor can deliver better range with less noise, but the larger number of pixels give the impression of increased focal length.  It is digital zoom instead of optical zoom, which is not nearly as clean.



" It is digital zoom instead of optical zoom, which is not nearly as clean."

Dear Camera click,

are you saying to me that i am better off buying a tele-converter for my 200x400mm on my full frame and losing at least a stop and some IQ as opposed to attaching it to my cropped D300.

As i've always been 35mm full frame since the year dot I use my D300 as many other birders do for the sole reason of it working as a tele-converter!


You can see the sample images above.  Both were taken through the same lens with the same settings.  The image of the Rogers sign from the Rebel is slightly larger at 100% crop, this has to do with the pixel density on the sensor, rather than the size of the sensor, I have a 30D body with the same size sensor as the Rebel and it does not exhibit the increased size at 100% crop.  Neither of the APS-C sensors give as clean an image as my full frame body.

In the next couple of days I will take a picture of the Rogers sign with a teleconverter and the same lens and full frame body so you can see the effect.


In the mean time, if you have a full frame body and a crop sensor body, try the same experiment, choose a target, take it with the lens on the full frame body, then move the lens to the crop sensor body and take another picture.  View both at 100%, or make a couple of 100% crops of 800 pixels or so, and compare them side by side.


Amazing Deals!

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