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I've been doing some reading on the Canon 5D recently and it set me to thinking why Canon released a full frame camera. Presumably they saw there was an opportunity in the marketplace that this could exploit. So I have 2 questions:

1. Will a full frame sensor produce better quality images than a DX size sensor when using the same lens and all other things being equal?
2. Does this make the Canon EOS 5D a better (albeit lower cost) camera than the Nikon D2x?

As a side note I notice Sheila Smart recently commented that, unlike her previous cameras, she needed minimal or no sharpening with her 5D, so this leads me to think the answer to my first question is probably yes.

Things I've read:

Full Frame = Shallower DOF + Wider angle of view (no crop factor)
Bigger Pixels = Lower Noise

Light falloff on edges of the frame (something to do with the angle of the light hitting the digital sensor

Diffraction limits are higher (Re: my post earlier today)

I'd say different horses for different courses.

Paul

stubbsy wrote:Will a full frame sensor produce better quality images than a DX size sensor when using the same lens and all other things being equal?

I'm no expert Peter but when comparing differerent sized sensors, things are never equal. If we talking similar total megapixels for both sensors, the FF will cream the DX as it's photosites are much larger and hence noise will be lower. If we are talking similar pixel size, then the noise should be similar, but the DX will have a reach advantage and the FF a WA advantage. The FF will also have more resolution but a much larger file size that has to be dealt with.. Six of one, half a dozen of the other.

stubbsy wrote:Does this make the Canon EOS 5D a better (albeit lower cost) camera than the Nikon D2x?
As a side note I notice Sheila Smart recently commented that, unlike her previous cameras, she needed minimal or no sharpening with her 5D, so this leads me to think the answer to my first question is probably yes.

The 5D and the D2x IMHO target different markets. The 5D is more of a landscape/portrait camera whereas the D2x with its' higher frame rate and "crop factor" would appeal more to birding/action/sport photographers looking for more MPs than a D2h can provide.

Other things to weigh up when looking at FF v DX include:
- Purported edge softness in FF images
- DX can use smaller, lighter and cheaper lenses for the same focal distance.
- As mentioned above, noise and WA issues with DX.

Thanks Paul & John

This is a more confusing subject than I thought. If I accept there is a light fallof at the edges with FF then I'd be guessing there'll also be a tendency to crop to fix that so maybe the FF comes back to DX size. This doesn't make sense though since it begs the question of why Canon would produce & sell a FF camera.

johndec wrote:Other things to weigh up when looking at FF v DX include:
- Purported edge softness in FF images
- DX can use smaller, lighter and cheaper lenses for the same focal distance.
- As mentioned above, noise and WA issues with DX.

And some of those aren't even that simple...

FF+: wider angle of view
FF-: more-susceptible to vignetting on some lenses, especially wide open
FF+(5D): larger photosites => typically cleaner images with lower noise
FF-: lens needs good performance over the larger frame
DX-: smaller photosites can sometimes resolve more detail than your lenses - need more expensive lenses.

When I was using a 3Mp D30 (1.6x crop) I told myself I could use cheaper lenses as I didn't care about the performance at the edges of the 135-format image circle. Today with a 30D I can't: the centre of the lens needs to have better performance than if I was using film!

stubbsy wrote:If I accept there is a light fallof at the edges with FF then I'd be guessing there'll also be a tendency to crop to fix that so maybe the FF comes back to DX size. This doesn't make sense though since it begs the question of why Canon would produce & sell a FF camera.

You're right: it doesn't make sense.

The FF camera is "more susceptible" to falloff, with certain lenses, in certain conditions. Not always.
In those cases where there is some vignetting, it's not uncommon to leave it. This happened with film after all!
And even if you decide to crop the image a bit, cropping all the way back to DX size would be a SIGNIFICANT crop.

stubbsy wrote:This doesn't make sense though since it begs the question of why Canon would produce & sell a FF camera.

Hi Peter,

it makes perfect sense: Canon sees a market for it, main competitor - Nikon, does not have a camera in that segment.

As others have mentioned, there are +/- to FF and DX, but there are also marketing advantages. For example, to people that have been holding out getting a dslr, going to a FF dslr would make it that much more attractive, their WA lenses are now still WA. Also, people buying the 5D are probably the ones that would buy the higher quality lenses, so Canon wins on that front.

Interesting question Peter,

Cheers,

Andre

Beware of "Marketing"
as in, "Don't step in that big pile of Marketing!"

Canon has the capital to fill in all the little gaps of it's product line, they make excellent cameras but I think they're a better advertising company.

I'm pretty sure Nikon will have a FF camera soon.

I personally hope that if Nikon do come out with a Full Frame that they keep up with the DX format as well.

I love the crop factor and the extra 'length' it gives my long lenses. Free teleconverter!

Paul

DaveB wrote:And even if you decide to crop the image a bit, cropping all the way back to DX size would be a SIGNIFICANT crop.

Looking at your figure I'd have to agree. So FF does offer more image. Unlike Grev, I'm not so sure a FF from Nikon is anywhere near happening.

stubbsy wrote:Looking at your figure I'd have to agree. So FF does offer more image.

Just think Peter... If you had a FF camera, then you wouldn't need to use your fisheye again...

What is the number of pixels you would need in a Full Frame to get the same 'resolution' of the DX sensor?

I ask this as I would think that if you only increase pixel count by (say) 4MP to 10MP total then the individual sensors on a FF would in fact be larger than those on a 6MP DX sensor. My maths may be off a bit, but it's Sunday and I don't have my calculator handy

If I'm right, and the pixel count isn't high enough, does that make a FF less sharp compared to the DX?

Does this make any sense?

sheepie wrote:What is the number of pixels you would need in a Full Frame to get the same 'resolution' of the DX sensor?

The d2x uses 5.5um pixels, while the 5D uses 8.2um ones, and it would get 19M of them onto a full frame sensor. According to this review anyway: http://www.gnyman.com/Canon5D.htm

edit: OK, that looked wrong so I did the maths, and emailed the dude too: 35mm is 24x36mm At 8.2um that's 36/0.0082 = 4390, then 24/.0082 = 2926 pixels, or 12.8MP. Officially the 5D is 4368 x 2912 which is within the rounding errors. At 5.5um the D2X is 6545 by 4363 or 28.6MP.

Having bigger pixels means you're less sensitive to lens sharpness (the same lens looks sharper) which is something that's been argued about for a long time - if the middle of a lens is generally sharper, but you're using it more intensely, are you any better off? People like Petteri are in the No camp, most Nikon users seem to be in the Yes camp (otherwise, presumably, they'd be using Canons ) I have no real opinion, I can't afford the FF cameras so it's academic.

sheepie wrote:What is the number of pixels you would need in a Full Frame to get the same 'resolution' of the DX sensor?

To estimate the number of pixels in a FF sensor with the same-size photosites the formula is: DX-resolution * 1.5 * 1.5.
D70 pixels: 6 * 1.5 * 1.5 => 13.5 Mp
D200 pixels: 10 * 1.5 * 1.5 => 22.5 Mp

If I'm right, and the pixel count isn't high enough, does that make a FF less sharp compared to the DX?

"Less sharp"? The smaller your pixels the more detail you can capture in the same field of view.
But when they get too small you exceed the resolution of the lens (no matter what the overall size of the sensor is) and I think that 22 Mp FF is close to (if not above) the limit of most of the Nikon/Canon glass at the moment.
At the same time, the more pixels there are the more pixels/mm there can be in the final print (ie. the less you have to enlarge the image) and this can be seen as lowering the resolution requirement of each pixel...

Nothing's ever simple!

Leon, i think you are thinking about 'pixel density' ie: how many pixels per square mm.

To attempt that logically;
Assume we have a DX and a FF DSLR at 10 megapixels each. If you use a DX lens on a DX cmos, then the 'resolution' should be no different to a FF lens on a FF camera. (Assuming the dimensions of pixels are the same (4000x2500) and you use a 50mm on the DX and 75mm on the FF to compensate for the crop factor.)

In the above example the FF would have larger 'photosites.'

leek wrote:Just think Peter... If you had a FF camera, then you wouldn't need to use your fisheye again...

Not really, there's a Canon 15mm f/2.8 fisheye which is basically the same FOV on FF as the 10.5 is on DX

Just been looking at the dpreview comparison of the D200 and the 5D - very interesting reading. If lenses weren't an issue then it would be a toss up for me between these two (although the current banding problems and lack of availability of the D200 is a minus).

stubbsy wrote:Just been looking at the dpreview comparison of the D200 and the 5D - very interesting reading. If lenses weren't an issue then it would be a toss up for me between these two (although the current banding problems and lack of availability of the D200 is a minus).

If you jump ship Peter, I'd happily take care of your current lens Give them a good home you know

stubbsy wrote:Unlike Grev, I'm not so sure a FF from Nikon is anywhere near happening.

Any reasons? But you know Nikon, they don't announce anything until they are ready for launch.

Grev wrote:

stubbsy wrote:I'm not so sure a FF from Nikon is anywhere near happening.

Any reasons?

I'm not expecting Nikon FF because none of their sensor suppliers have one, and none are talking about it. It wouldn't surprise me if the first we heard was a Nikon announcement, but I would expect it to be at least a year between the Nikon announcement of the new camera and actually seeing one in real life. So don't hold off on that D200 :)

An interesting question is what pixel size they'd use. Putting 28MP into a DSLR would mean that unless they radically revise their data transfers you'd be looking at 2-3 fps (for the same data rate 5fps @ 12MP becomes 2fps @ 28MP). But they've got their users trained to accept 5um pixels, so selling the better noise characteristics of bigger pixels would come under "shooting your cheaper models down in flames". Perhaps this is where the Zeiss deal comes in too, as Zeiss might actually be able to make a lens good enough to work with a 28MP FF camera.

The real reason is probably price - could Nikon maintain their pricing comparison with Canon if they went full frame? They'd need to be at least similar to sell in reasonable numbers, and the question of whether Canon made a profit on the 1Ds series is IMO still open. Add the overhead of getting Sony or someone to build the sensor and I think they'd need to sell a huge quantity of cameras, pushing the price point under the 5D. I just don't see a win position for Nikon.

stubbsy wrote:

1. Will a full frame sensor produce better quality images than a DX size sensor when using the same lens and all other things being equal?
2. Does this make the Canon EOS 5D a better (albeit lower cost) camera than the Nikon D2x?

1) No. Larger sensor sizes in the current DSLR's do not guarantee greater image quality. My partner shoots with two 5D's and it's a nice camera, but image quality has more to do with what you stick in front of the sensor then the size of the sensor.

2) No. Sensor size is just one part of the puzzle when buying/using a camera. Eg D2x is faster for sports action, where as the 5D/30D is better at high ISO. Your application should guide your camera selection. 5D isn't better or worse, just different.

I'd love a FF F-mount, so i can get more out of my current glass.