EF-S vs EF

[alex2074]

I am the owner of a 20D, which suits me just fine, it does all things I could ask for.  I would like to buy some lenses made particularly for the EF-S series like the 10-20mm and the 17-55mm f2.8.  I scan craigslist and ebay to see what is out there and nearly everybody dumping their EF-S gear is doing so because they went to the 5D.  So my question is, what is so special about full frame cameras?  And considering that the EF-S fixture allows canon to create lenses for it that it can not do for the full frame, why such the exodus?   Am I mistaking in thinking that the lens capability is what really matters, and not the size of the camera?

[Ray]

I am the owner of a 20D, which suits me just fine, it does all things I could ask for.  I would like to buy some lenses made particularly for the EF-S series like the 10-20mm and the 17-55mm f2.8.  I scan craigslist and ebay to see what is out there and nearly everybody dumping their EF-S gear is doing so because they went to the 5D.  So my question is, what is so special about full frame cameras?  And considering that the EF-S fixture allows canon to create lenses for it that it can not do for the full frame, why such the exodus?   Am I mistaking in thinking that the lens capability is what really matters, and not the size of the camera?

A full frame 35mm sensor has 2.5x the area of a 20D. For any shot of the same Field of View it will gather 2.5x the amount of light, at the same shutter speed, f/stop and ISO. Provided the technology and design is on a par, the full frame sensor will therefore produce a higher dynamic range, lower noise and higher resolution. Is that sufficient reason to get one?  

Apart from lower weight and lower cost, I can't think of any advantages the 20D would have that the 5D2 doesn't also share. The 5D2 even has the same reach with long telephoto lenses because the pixel density is that same as that of the 20D. The EF 16-35 on the 5D2 will produce equally wide results as the EF-S 10-22, but also, as I mentioned, higher resolution, higher DR and lower noise.

[jjj]

I have a mint condition 20D [gathering dust somewhere] and a very battered 5D. You just have to look through the viewfinder to see how much better things look due to the reduced depth of field and bigger viewfinder area. I never liked using a crop sensor as my 16-35mm + 24-70mm were much less useful ranges  - 26-54mm + 36-105mm, there are wider options now, but slower than FF zooms.
The 20d seems a bit well crap when compared to a 5D - in my view. Good camera in its time though

[stever]

i'm still using a 20d because i have an underwater housing worth way more than the camera, and since added a 40d (nicer to use, barely noticeably better IQ - i also tried a 50d which was an improvement over the 40d with some lenses but still inferior to the 5d) , 5d which provides significantly more pleasing images at 13x19, and now a 5d2 which is a huge jump in both IQ and useful features over the 5d.

there's a theory that crop-frame cameras can provide better performance with mediocre lenses since they only use the central "best" part of the lens.  in my experience, the full frame cameras out-perform the crop frame cameras on nearly all lenses - which i don't understand - and the 5d2 substantially out-performs the 5d on my 100-400 which i previously thought to be better matched with lower reslolution crop-framed cameras.

i think Ray is pretty much on the money as i can't see a significant difference between the 40d and 100-400 at 400 (640 equiv) and the 5d2 cropped.

the other problem is that canon has made a limited investment in S series lenses - the 10-22 isn't bad, and the 17-55 has good IQ but mediocre build quality, but the other S lenses don't even realize the resolution potential of the 20d, let alone the 40d and 50d.  Canon has determined how they'll segment the market and crop frame cameras are not going to compete with full frame, even if they could technically.

[alex2074]

Ray,

The 5D may have a 2.5X size CCD, but that says nothing about the light that it actually receives relative to the crop frame.  For the statement '2.5X the light'  to be true the lens would have to let in 2.5X the light, and both crop and full frame cameras both accept the same EF lenses.  So the 5D really gets the same amount of light as the 20D, but because it is spread over a larger area the sensitivity is reduced, making the 20D actually better in this regard.   Where am I wrong?

what came first, the 10D series or the 5D series?  If the 10D came first, does that mean that canon is just keeping that line going because the market is already flooded and small adjustments to each next generation is pretty easy, and people who dont want to spend the money on the 5D can be satisfied?

Ill have to try out the 5D and compare it.  It just seems to big and bulky.  

[Ray]

Ray,

The 5D may have a 2.5X size CCD, but that says nothing about the light that it actually receives relative to the crop frame.  For the statement '2.5X the light'  to be true the lens would have to let in 2.5X the light, and both crop and full frame cameras both accept the same EF lenses.  So the 5D really gets the same amount of light as the 20D, but because it is spread over a larger area the sensitivity is reduced, making the 20D actually better in this regard.   Where am I wrong?

The concept here is not that the lens lets in 2.5x the amount of light, but that the FF sensor captures 2.5x the amount of light. Consider the same lens at the same focal length, using the same shutter speed and same f stop, on both formats. The lens must let pass the same amount of light. However, the cropped format crops the field of view and therfore crops, or reduces, the total amount of light bombarding the sensor. In this scenario, the field of view is unequal. However, it's true the same amount of light falls on the same area of sensor.

However, when we adjust F stop and focal length so the field of view is the same for both formats, the composition receives 2.5x the amount of light in respect of the full frame format. Okay?  

Edit: It's tricky, and I get myself confused sometimes. A 50mm lens at F8 lets pass the same amount of light as an 80mm lens at F13. The physical aperture diameters are the same. 50/8 = 80/13 (approx). The FoV is the same, but the FF sensor is 2.5x larger and therefore captures 2.5x the amount of incoming light. The cropped format wastes a lot of the image circle of the FF lens, hence the introduction of EF-S lenses, which are designed to be (hopefully) sharper in the centre but would be hopeless at the edges, if they were able to fit onto a FF DSLR.