Cropped Vs Full Frame:

What is the correct sensor type for your photographic style?

Given the relevance of this topic these days I thought it a subject worthy of thorough discussion. Is full frame still the holy grail of DSLR’s or have the lines blurred somewhat? Unfortunately I’ve no pretty pictures to add except a few boring ones at the end so it is mostly text, but if you want to know everything you need to know about what is the right sensor size for you and your style of photography then read on. I promise not to bore you!

For most people, when purchasing their first DSLR they will more than likely go for an entry level or enthusiast level model. First time DSLR owners are normally oblivious to the fact that cameras have different sensor sizes. It is only when they delve further into the subject of photography that they realise that this is the case and sometimes that may be too late as the camera is already bought. To explain where the terms full frame and cropped frame come from we need to step back in time and delve into the photography history books a bit. Back at the turn of the 20th Century a company called Leica, or more accurately named Ernst Leitz GmbH at the time, brought what is now regarded as the gold standard for film cameras, the 35mm film, to the general public. This film size was an adapted version of a film size that existed at the time but never really worked. So this new 35mm size (or more accurately 24mm x 36mm) instantly caught on and the rest you might say is history. Since the creation of the 35mm film format a number of other, smaller film sizes were developed but none truly succeeded as they were a compromise on quality. I remember this vividly, family holidays back in the 80’s and early 90’s for me were also followed by a trip to the photo guy to develop the numerous rolls you took on holidays only to find out the photos were actually horrendous and really only good for the bin. Oh how we have advanced!

So, here we are in the 21st Century, surrounded by digital cameras of all shapes and sizes. But how do these new-age digital sensors compare to the film cameras of the past? Well, quite simple really, they classify their sensor size according to the standard 35mm format. In fact, almost everything “camera”, from the big ones to the small little compact cameras, harks back to the 35mm format in some way or another but we’ll come back to this in a minute.

In the world of digital cameras, the equivalent of a 35mm film camera is called a full-frame camera. This means the sensor in the camera is the same size as a frame of the old 35mm film, 24mm x 36mm. It is labelled a full-frame sensor and Cropped Vs Full Frame Sensors when it comes to DSLR sensors it is the cream of the crop. A smaller sensor is called a cropped frame or APS-C sized sensor and is determined by a crop factor (1.5 for Nikon DX cameras, 1.3 or 1.6 for Canon, 2.0 for Olympus, Fuji and Kodak). So in terms of a Nikon DX camera (D90, D3100, D5100, D7000, D300s etc.) the sensor size is 66.7% the size of a frame of 35mm film. For Canon Rebel, 550D, 60D, 7D, the crop factor is 1.6 so the sensor size is 62.5% of 35mm film. For older Canon 1D series cameras the crop factor is 1.3 meaning the sensor size is 77% the size of 35mm film. This sensor is no longer produced by Canon.

The big question now is why? Why do camera manufacturers produce sensors that are smaller than full frame if full frame was always best back in film days? To answer this correctly we need to break it down into a number of individual topics:

  1. Sensor cost.
  2. Image quality and low light capability.
  3. Lens specifications and focal length issues.
  4. Depth of field

The most obvious cropped versus full frame argument is price. A full frame sensor is bigger than its cropped little brother so it must be more expensive to manufacture. A bigger house is more expensive to build than a house 60% its size in the same part of the city no? Well it is true, sensors, like houses increase in price the bigger they are. Medium and large format sensors (with even bigger sensors than 35mm) are far more expensive to manufacture than full frame sensors. So it is a case of, the bigger the sensor, the more expensive the sensor and consequentially the more expensive the camera. As a result this puts full frame cameras out of reach in terms of price for most amateurs. But I don’t think it will be this way for long. When you think of it, digital cameras are really only in their infancy. They are what, a little over 10 or so years old (at time of writing in 2013) as it was the beginning of the 21st century when they actually started catching on with the masses. Sensor technology has come a long way in that time if you think about it. 10 years ago a 4MP camera was state-of-the-art. Now you can pick up a 36MP full frame for a little over €2k. For this reason I can see the price of full-frame cameras dropping significantly over the next decade and becoming more accessible to first time camera buyers. The Nikon D600, the cheapest full-frame camera on the market confirms this. But until then, camera manufacturers will continue to produce full-frame cameras that are well out of reach of first time buyers. They will also continue to put their full frame camera range on a pedestal, teasing cropped frame camera owners with a type of keeping up with the Jones’ mentality. “Did you see Peter, he just bought a new full frame Canon”, I need to get one, I need to get one, it is better, it takes better pictures!”

But are they better, do they produce better pictures? Up to last year I would have said yes, but things have changed a bit. Full frame cameras were known for their better low light or ISO noise performance. The reason for this was related to photosite size. Sensors are composed of millions of these photosites, more commonly branded as pixels. As the theory goes, the bigger the pixel the better the ISO noise tolerance. Full frame sensors by their very nature were bigger and consequentially had bigger pixels. In other words, the pixel size in a 12MP full frame sensor was bigger than its little sibling in a 12MP cropped frame sensor. This makes sense no? After all, if a Nikon full frame sensor is 1.5 times the size of its cropped frame little brother then the full frame pixel is 50% bigger if the megapixel count is the same for both sensors? In terms of size this would be correct but in terms of ISO performance I think this argument is out of date.

Being a Nikon user I can only comment on this brand as it is all I have tested but in terms of technology, sensors are the same and they are advancing at a phenomenal rate so this argument applies to all brands. I did a comparison of the ISO noise handling of the Nikon D700 and the Nikon D800. The D700 has a 12MP full frame sensor whereas the D800 has a 36MP full frame sensor. So the D800 crams in a whopping 3 times the number of pixels of its older brother. The immediate assumption would be that the ISO handling of the D800 would be significantly worse. In fact, before I bought one I was chatting to various “professionals” in camera shops and they shared the same opinion, “yeah, the D800 is a great camera but for low light it is pretty poor”. These were the guys selling me the camera! So, I waited, . . . . and I waited, . . . . and I waited a little more until DxO Mark released their research on the D800 sensor. Upon seeing the results I ordered one straight away. To put a long story short, the D800 has at least one f-stop better noise (ISO) performance than the D700. This is incredible, a camera with pixels 1/3 the size of the previous generation having better noise tolerance, how can that be? Call it advancement in technology; the same way a first generation iPad feels like an antique against the newer versions, camera sensor technology is advancing at a similar pace. Sensor size is becoming far more irrelevant when it comes to ISO performance that the old argument is becoming more difficult to justify. And it is only going to get better. That is why I constantly urge people to invest in top end lenses as opposed to camera bodies. In ten years’ time ISO’s of 25,600 will be standard across even entry level DSLR cameras.

So if ISO has little bearing on image quality then why would you pay more for the full-frame sensor? For me personally, the main reason is the quality and selection of lenses available. Full frame lenses by their very nature are better built than their cropped frame counterparts, they have less optical flaws and are made to last. There is also more of a selection and they usually have wider apertures. A wider aperture means better depth of field control and better quality in low light conditions. They also let more light in as they are designed for the bigger full frame sensors. The added bonus here is that they make the viewfinder brighter. Of course you can use a full frame lens on a cropped frame camera but you are wasting 50 per cent of it. You are effectively cutting off 50% or more of the field of view on a cropped frame camera. Professional full frame lenses are known for their edge to edge sharpness, massive amounts of engineering goes into achieving these qualities. Mounting it on a cropped frame sensor wastes all of this effort and ultimately is a waste of your own money. The only reason I would suggest a cropped frame camera owner buy a full frame lens is if they intend in the near future to upgrade their camera body to full frame and are simply future-proofing their lens purchases. Otherwise, forget it, you are wasting your money. Buy a cropped frame equivalent; it will be cheaper, lighter and more specific to your camera.

Cropped Vs Full Frame SensorsIn terms of focal lengths, full frame and cropped frame cameras operate differently and the focal length differs by the crop factor we spoke about previously. To put it simply, every lens out there will have a single focal length (prime lens) or a focal length range (if it is a zoom). 50mm prime, 85mm prime, 18-105mm zoom, 28-300mm zoom, all of these lenses have their own specific uses, but the important thing to remember here is that the numbers represent the focal length only when mounted on a full frame camera. If you mount them on a cropped frame camera their focal length changes according to the crop factor of the sensor. OK, this is the complicated bit and if you have not come across this concept before then it does take a bit of thinking. Let’s use a couple of pictures to demonstrate how it actually works.

To the right we have two pictures, the first taken with a full frame camera (Nikon FX), the Cropped Vs Full Frame Sensorssecond with a cropped frame camera (Nikon DX crop size). I have the camera metadata showing so you can see the focal length for both images. You can see fairly quickly that the DX image is the middle section of the FX image. Why is that you may ask yourself? Well simply put, because the DX sensor is 66.7% smaller in size than the full frame FX, it is only going capture 66.7% of the image of the FX. Make sense? Now, I used a 70-200mm zoom at 100mm for both pictures but both photos are different. The DX photo looks like I used a longer focal length (bigger zoom) than the FX, but I didn’t, I used 100mm.

Cropped Vs Full Frame SensorsTake a look at the little diagram to the left. This is a very simplified comparison of a cropped and full frame sensor working in real life. Full frame is blue, cropped is red. In the first part of the diagram you can see that the focal length is the same for both sensors. You can also see that the resulting image captured by the cropped frame sensor is essentially a “cropped” version of the full frame image. Or in other words it is a magnified or zoomed version of the full frame image. The reason it looks zoomed is because, as you can see it is capturing less of the scene and to replicate the same picture on the full frame sensor I will need to zoom in. This can be seen with the longer focal length for the full frame sensor as is shown in the second part of the diagram. This is a simplified diagram but in essence this is how it works in the real world.

The question now is how much do you need to zoom in on a full frame camera to replicate the image of a cropped frame? For our previous example above, let’s try out a few focal lengths until we get more or less the same photo as the DX. Below you can see various focal lengths on the full frame camera. You can also see that at 150mm the FX full frame photo looks more or less identical to our original 100mm DX image. In other words I need a 150mm focal length on my FX camera to give me the equivalent of 100mm on my DX. I need a focal length on my FX camera that is 1.5 times that of the focal length on the DX cropped frame camera to provide me with the same image. It is no coincidence that you need 1.5 times the focal length since the FX sensor is in fact 1.5 times bigger than a DX sensor. If I have 200mm on my DX camera, then I need 300mm on my full frame to give me the same image (or 320 if a 1.6 crop Canon was used, or 400 if an Olympus was used etc). To sum it up, you need to multiply the full frame focal length by the sensor crop factor to get the true focal length on a cropped frame sensor. Easy isn’t it!!

So now that we have defined how the crop factor of your sensor correlates with lens focal lengths let us take the simple 50mm prime lens. On a full frame camera it is 50mm, But on a Nikon DX it is 1.5 times this which is 75mm. On a Canon with a 1.6 cropped sensor it is 80mm equivalent. So your cheap and cheerful 50mm f/1.8 lens turns into a great portrait ranged focal length on a crop camera. Great isn’t it? Well no, not really. What if you really need 50mm on your cropped frame camera because you need a wider field of view? Well in this case you would need to have a 35mm lens to give you a near equivalent 52.5mm on DX or 56mm on 1.6 crop Canons. What if you are a full frame landscape photographer and you love your 14-24mm f/2.8, the goddess of wide angle lenses for your Nikon. This lens is a top-end ultra-wide angle with superb sharpness for such a wide field of view. For the DX format photographer there is no lens that gives this field of view. You can get a 10mm but you lose 1mm in field of view. Although 1mm is a small price to pay (the 14-24 f/2.8g FX lens is €1.5k, a 10-24 DX lens is half that) the bigger consideration here is image quality. Because a cropped lens requires shorter focal lengths to achieve the same field of view of a full frame the shorter focal length must compromise on image quality. The wider the angle the poorer the image quality, this is an unfortunate optical truth.

For wildlife, nature or sports photographers cropped frames rule for the focal length issues just mentioned. For a wildlife photographer, or a daylight sports photographer shooting stuff at large distances, zoom is in fact your friend and the cheaper and lighter the zoom the better. Taking a focal length of 400mm which is a pretty serious telephoto focal length, and what your sports or wildlife photographer is probably after, you are paying serious cash for a good FX version. You could buy small cars for the same price. You also need a crane to bring them around with you. They are massive and will probably crush vertebrae if you plan on backpacking one around with you. All you need to do is look on the side lines at football or rugby matches to see lines upon lines of these monsters. Huge! In the case of a cropped frame, a much smaller and far less costly 300mm lens will give a longer focal length. Not only does it cost a fraction of the other lens, it is only a fraction of the weight too. When you are a wildlife photographer out on safari, light is always good!

In terms of depth of field the larger the sensor the shallower the depth of field. This is because you need to get closer to your subject with a full frame sensor or use a longer focal length meaning more compression. Depth of field and focal length go hand in hand. So an f/2.8 on a full frame camera will produce a shallower depth of field than that of a cropped frame camera when composition is kept constant (subject fills the frame in both instances). Or in another way, to keep the depth of field constant across cropped and full frame you need to use a smaller aperture on your full frame camera than on the cropped frame camera. The same reasoning applies for a medium or large format camera; these will produce shallower depth of field than a full frame with the same aperture. So if you are a lover or shallow depth of field then you should seriously consider going full frame. You simply will not get the same results using a cropped frame camera with the same aperture.

Summing it all up: If you are the owner of a cropped-frame camera, be proud; don’t think you own only half a camera, you own a precision tool that has serious advantages over its full frame counterpart. Your gear will be lighter, easier to carry and a lot cheaper so you can go on more holidays with the money you have saved without the risk of crushing vertebrae while backpacking with your gear. If you own a full frame camera be proud also, you have the greatest selection of lenses available to you, you can take more artistic photos in terms of depth of field, your portrait or wedding images with shallow depth of field will be more beautiful, you can take better landscape photos and more than likely you can take better low light photos (without flash) than your cropped frame buddies. I do believe this ISO performance gap will narrow in the near future though, so don’t gloat! It is hard to say what way the cropped versus full frame battle will go; the big name camera manufacturers may keep up their marketing tricks, branding the full frame range as their elitist, bees knees range for true photographers keeping the uneducated cropped frame owners drooling. They may continue to reserve the high-end professional functions for their full frame cameras which will be a shame because the cropped sensor is a true and sensible choice for some photographers, they should be given the option to purchase a cropped frame camera with all the pro options. But, unfortunately it is not to be. It is hard to say which way it will go. Suffice to say, if you haven’t got the cash to spare and aren’t massively fussy on lens availability then a cropped frame camera is certainly for you.

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