Cropping and crop cameras

Eisbar

Eisbar

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257
Name
Richard
Edit My Images
Yes
I mainly shoot landscapes and portraits. For this I use my 1Ds MkII and am very happy. I occasionally shoot sports, my kids at sports day etc. and indoor events, school play etc.

I recently sold my 40D as I wasn't using it much. I now find that my 200mm f/2.8 isn't long enough. Using a 1.4TC is OK but I still need a bit more reach.

My options are therefore-
i) buy a longer lens - 300mm f/2.8 very expensive but presumably best option
ii) buy a crop body - 40D was OK with f/2.8 but ISO above 800 was starting to get noisy (is the 50D any better?)
ii) crop my images

Option i is out of the question due to expense. I seem to remember reading, I'm not sure where, that option ii is better than option iii.

Could some slowly explain (preferably with the aid of a diagram) why using a cropped body is better than cropping a full frame image. I seem to remember that it's to do with pixel density but the explanation lost me fairly shortly after that.

Many thanks
 
The only difference between a full frame camera and a cropped one is the size of the sensor and the pixel density.

A 5d captures all that a 40d sees, but also the bits that are missing because the sensor is 'cropped'.

Check out 'CT' and his amazing wildlife shots with a 50d. Truly awesome and with a 50d too.

Graham
 
its the pixel density thats the thing as to get same px density you need a lot more px on full frame

cropping is your cheapest option 300 f2.8 is your best all the others fall in between :D
 
Eisbar said:
Could some slowly explain (preferably with the aid of a diagram) why using a cropped body is better than cropping a full frame image. I seem to remember that it's to do with pixel density but the explanation lost me fairly shortly after that.
Click to expand...
OK, I'll try to make a start.

The first thing to remember is that, with a crop-sensor camera such as the 40D, you're not seeing as much of the image projected by your lens as you are with a full-frame camera. That's all that's happening. Nothing else. Here's a picture to illustrate it.

Crop-factor-demo-1.jpg


Now your 1Ds Mk II has 16.6 MP spread over the area of the red rectangle, so if you do the arithmetic you'll see that it has 6.5 MP within the area of the blue rectangle. (The crop factor is 1.6, so the calculation is 16.6 divided by 1.6 squared, i.e. 16.6 divided by 2.56.) However, your old 40D had 10.1 MP spread over the area of the blue rectangle, which is roughly 50% more pixels.

So a 40D image will have 50% more pixels than an equivalently-cropped 1Ds Mk II image. Clearly that means you have more scope to crop the image further with the 40D than with the 1Ds Mk II.

Some points to bear in mind though (if not for you then perhaps for other people reading this who have different cameras):

1. This calculation is just for a 1Ds Mk II vs a 40D. With a different pair of cameras the results might be diffferent. For example, comparing a 1Ds Mk III (21.1 MP) with a 30D (8.2 MP), you'll see that they both have the same number of pixels in the blue rectangle.

2. Not all pixels are equal. Other things being equal, bigger pixels are better than smaller pixels, because they are better at capturing light and therefore produce less noise. But also, other things being equal, newer pixels are better than older pixels, because the electronics will have improved and they will produce less noise. In your case, the 40D is newer than the 1Ds Mk II (it came out at the same time as the 1Ds Mk III) so it's pixels are smaller but newer - and it's not easy to work out from first principles which will be less noisy.

How far does that get you in your understanding? Any follow-up questions?
 
That's a fantastic illustration to show how a cropped sensor works v full frame. (y)
 
Cheers for the replies. Many thanks for the diagram and explanation Stewart, it was the 1.6 squared that had me confused.

So looks like I'm possibly in the market for a cropped body again!
 
If I was the OP, and having a generous helping of pixels in the 1Ds, I think cropping the full frame image quite hard to gain reach might be good enough, depending on how critcal you needed to be. Obviously the easiest and cheapest option, and still presenting at least as many pixels as my old 350D which I'd not hesitate to use in similar circumstances.

Having the 1Ds fitted with a super-sharp 200 2.8 is also a very good start, although the 1.4x TC (hoping it's the Canon one) will certainly take the edge off it. The point I make is that investing in a modern crop body, while obviously better, might not be such a big jump up.

That's just a guess though; never tried it. Seems worth a punt though ;)
 
HoppyUK said:
If I was the OP, and having a generous helping of pixels in the 1Ds, I think cropping the full frame image quite hard to gain reach might be good enough, depending on how critcal you needed to be. Obviously the easiest and cheapest option, and still presenting at least as many pixels as my old 350D which I'd not hesitate to use in similar circumstances.

Having the 1Ds fitted with a super-sharp 200 2.8 is also a very good start, although the 1.4x TC (hoping it's the Canon one) will certainly take the edge off it. The point I make is that investing in a modern crop body, while obviously better, might not be such a big jump up.

That's just a guess though; never tried it. Seems worth a punt though ;)
Click to expand...

That's what I'm doing at the moment. Just starting to regret selling my 40D as the extra reach was useful at times. I found I wasn't using it much so I sold it but now have found that on a couple of occasions I'm missing it.

TC is a Canon
 
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