Wednesday, October 22, 2008

Photography: The Crop Factor

This is actually a request, or a suggestion from our reader Rob over here. He asked me a while back (quiet a WHILE back) to explain the crop factor. So here it goes, i m going to try to explain it as good as i possible can

Lets first start by lining up the type of sensor that are available out there:
DX, full frame, APS-C, crop factor, 24x36, image circle - honestly i didnt know that all of these existed untill i wrote this article i was only aware of full frame and DX.

Back in the good old days (film days that is) the "sensor" if you will, measured 24mm x 36mm, that was for some time the "standard" size of all SLR´s back in time. But these days when things have moved over to digital things have changed a bit

Depending on what manufacturer you choose the "crop" factor and the sensor size will be different. Note that "crop" factor and sensor size is pretty much the same things, its talking about the sensors crop factor equivalent to the standrad 35mm film. Do you follow here? Great if you do so.

Nikon has two different sensor sizes: full frame (also known as FX), and 1.5x (DX)

Cannon has three different sizes: full frame, 1.3x and 1.6x

Olympus has one size that i m aware of: 2x

Below is an image trying to illustrate the crop factor:

So why is this sensor talk important? Well it is, because every sensor type has its advantage and disadvantage.

As a rule of thumb (dont bash me here) full frame sensor have better image qualiy, specially when it comes to higher ISO´s performance.

So lets put this into practice, a great example is Nikons D300 (1.5x) vs D700 (full frame):

The D300 is one of the best non-full frame cameras out there when it comes to ISO performance, its will give you some very good results at the higher ISO´s but the D700 will give even better results: so lets put some numbers in here just to make things easier. You will start to loose alot of iamge quality on the D300 above ISO 16000 while the D700 does that at ISO 64000. And why is this? Well its because of the sensor size, note that both camera have a 12MP sensor, so there is no differnece there. So on the D700 the pixels are bigger thus rendering a better dynamic range and noise performance, and therfore giving you a clearer image at higher ISO´s (check this link out for ISO comparisonts over at cameralabs)

Frull frame is something that is pretty good to have when it comes to landscape photography; why? Because most (but not all) cheaper primes and wide angle are pretty much made for full frame. An example of this is that you can pick up a 24mm f/2.8 prime lens for about $300 while the DX 12-24 f/4 will run you about $900, so that is quite the difference.

While a down side to full frame is that the lenses are some what more bulky and big, but from what i read around the web people seem to be enjoying carrying around kilos of stuff. Another thing to note is that full frame bodies are some what more expensive these days (still dont know why, marketing maybe?)

Now the croped sensors have its advantage when it comes to using longer focal lenghts, for example if you get teh 70-200mm f/2.8 you will get a 105-300mm f/2.8 lens on a croped body (1.5x) this means that you will have almost the double reach with the same aperture, while a teleconverter would be needed for the full frame camera and thus you would loose a couple of f-stops.

So what should you choose when getting a new DSLR?

Well if your used to have a SRL and have a nice lens collection for that, it wouldnt be bad to spend the extra cash to get that full frame body so you can use those lenses specially if your into landscaping, it will save you alot of cash!

If you shoot at low light, it can be quite a pickle. Because lets be honest here, the D300 for example renders some really good results at higher ISO, but the full frame renders better. What i can say here is that it all comes down to what else your going to use the camera for, plus size is thing to take into consideration (even tho there isnt THAT big of a differnce between the D700 vs D300)

But if your into shooting wildlife and animals etc a croped body could be a great bennefit for you, because you will get that extra reach without having to spend the money on teleconverters while loosing f-stops.

I hope i cleared some things for those whom where wondering about crop factor and sensor size


Bjorn van Sinttruije said...

And Sony has 1x (Alpha 900) and 1.5x (all other models).

Good to see you blogging again Alex!

Alexander Blacker said...

Thanks Bjorn, will add that when i do my next entery today!

Dont know much about sony as u can tell, but ur the man when it comes to sony!