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The Full Frame Myths

Started Aug 26, 2014 | Discussions thread
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The Full Frame Myths
Aug 26, 2014

As Full Frame camera prices fall, the once fabled Full Frame digital camera is now within reach of many hobbyists. Floating in the internet, the number one place novice and buyers are looking for information, are the many Full Frame Myths, they pop up every time someone asks if which Full Frame camera they should buy, or if they should upgrade to Full Frame. The people who repeat these myths have differing motives; some are merely innocently uninformed trying to be helpful, some have a despite need to validate their own purchase choice, some may have even more sinister motives which I will not waste time divulging. In this post I will examine and explain the these common myths around Full Frame.

Myth Number One : Full Frame cameras lack DOF

This myth argues that since Full Frame cameras can provide shallower DOF, they cannot produce deep enough DOF when required. The level of its ludicracy is genuinely bizarre. Almost all lenses designed for the 35mm Full Frame system can be stopped down to F16, about half of them can be stopped down further to F32. Suffice to say, at F16, you will have sufficient DOF 99.9% the time. For the rest 0.1% time, you will have either diffraction so strong that you don’t want stop down further shot anyway or the desired DOF is so impossible even smaller format will not do. The best solution is usually stacking.

20mm F8 on FF

Myth Number Two : Full Frame cameras are always bigger and heavier than comparable smaller formats

While by necessity of having to house a larger sensor (and often larger mirror and viewfinder) Full Frame bodies are generally bigger than smaller formats, Full Frame cameras on the other hand can be smaller than equivalent cameras smaller formats. This is because Full Frame lenses are smaller than equivalent lenses of smaller formats. An equivalent lens is one that has the same Field of View and the same actual aperture size which will result in the same framing, same Depth of Field and same total light falling to the sensor, therefore generating similar looking output image. When FOV and actual aperture size are held equal Full Frame lenses have smaller F ratio; that in turn results in simpler design and less expensive glasses. In contrast lenses of smaller format have larger F ratio which requires more expensive glass, and more complex design to correct optical problems caused by having a large F ratio. For example, consider the Canon 60D + 17-55/2.8, it is equivalent to 28-88/4.4 in Full Frame terms; the comparable Full Frame lenses are Nikon 24-85/3.5-4.5 VR and Canon 24-105/4 IS, Both Nikon D610 + 24-85 and Canon 6D + 24-105/4 are smaller than 60D + 17-55.

The D610 with 24-85 is even smaller

Myth Number Three : Full Frame cameras always require more expensive lens than smaller formats

This common myth comes from the observation that Full Frame owners often use high end lenses. But that is not because Full Frame cameras need them, but rather, Full Frame owners are often happy to spend top dollar on the hobby, hence them owning Full Frame in the first place. But the truth of the matter is, on the contrary, to produce equivalent final image Full Frame cameras actually require less expensive lenses. There are two reasons for this. The first reason is what we already covered in Myth Number Two – Full Frame requires lenses with smaller F ratio for equivalent image. As most seasoned camera owners would know, lens price increase geometrically with F ratio increase, it is because lenses become exponentially more complex and requires more correction as F ratio increases (using the example from the previous Myth, 17-55 IS is more expensive than Nikon 24-85 VR). The second reason is that Full Frame lenses require less per area sharpness to produce an overall equally sharp image as smaller formats. For example, m43’s sensor is about ¼ the size of an Full Frame sensor, that means, to produce the same output resolution, assuming sensors have the same pixel count, the m43 lens needs be 4 times as sharp. That in turn means much higher quality of glass required, 4 times higher level of precision, polish, and tolerance, they all add up to the price very quickly.

18mp FF + $100 lens vs 16mp FF + $200 lens vs 16mp m43 + $600 lens at equivalent setting.

Myth Number Four : Full Frame cameras have less reach than smaller formats

This myth comes from the 20 year old marketing effort by all digital camera makers. Because the sensor has been the most expensive part of the camera, instead of having to explain why digital cameras have smaller sensor size than the size of standard 35mm film, camera makers span it into an advantage. They claim by cropping FOV, you get the same FOV as longer lenses therefore you effectively got a longer lens! Indeed many people buy into this myth, partially because many of them bought a smaller format and love to believe they got that “extra value”.

This myth is false for several reasons. First, Full Frame cameras can crop just the same. A D800/A7R can crop down APS-C sized image while maintain the same resolution as D7000/NEX5. People do not tend to say D7100 has significant more reach than D7000 or that NEX7 has significantly more reach than NEX5.

Secondly, with imperfect lens, mere increase in sensor resolution does not significantly improve image resolution; in fact often there is no improvement at all. For example, D7100 has same pixel count as D610, which in theory means it could have up to 50% more reach than D610, but there is no lens that can enable D7100’s to obtain that level of extra reach. If we look at a commonly used high end lens - 70-200VR II, we see that at 200mm end, the D7100 would produce as final image with roughly 6~7mp of detail. A D610’s centre crop is about 11mp, with that lens at 200mm, it too will produce roughly 6mp. In other words, due to the lens’s imperfect resolution, there is no gain in having the extra pixel count and therefore is no extra reach.

But thirdly and most importantly, as we had already discussed, Full Frame cameras require smaller F ratio for equivalent image, and as we had already discussed, Full Frame cameras require cheaper lenses to produce the same resolution. The net result is that Full Frame cameras can use cheaper, less sharp and longer lenses to match smaller cameras with more expensive, sharper, higher F ratio and short lenses. For example a D610 with the 1000 dollar Tamron 150-600 will produce same or sharper image than that from a D7100 with the 2400 dollar 80-400G. While the 80-400 has larger F ratio(5.6 vs 6.3) and higher quality glass (hence the much higher price), it projects image onto a sensor 2.25 times smaller, So unless the 80-400G at 400mm is 2.25 times sharper than 150-600 at 600mm, it will produce less resolution. So in fact, under certain conditions, one would get more reach by going Full Frame over smaller formats!

Myth Number Five : Full Frame cameras have no IQ advantage because you need to stop down further to get sufficient DOF, and to maintain the same shutter speed you need to increase ISO proportionally which nullifies IQ advantage.

This myth is actually true under certain circumstances. But the reason I consider it a myth is because it is often presented as if it is true 100% the time. In the real world they do not happen very often (actual likelihood depends on individual’s preferred shooting style). That is, where you cannot reduce shutter speed further because it will cause shake or motion blur and you cannot add more light to the scene. In the real world, for serious portrait photography, shooting takes place either in good light or with flash, in both cases shutter speed generally does not have to drop below minimum safe range after stopping down to warrant increasing ISO. For serious landscape shooting, there will either be sufficient light, or one would be bringing a tripod. For wild light or action shooting, since shooting takes place at a far distance, there is generally enough DOF even with lens wide open. For serious macro photography, there should be stacking and good flash system in place. It is only in casual shooting where you do not have additional lighting, do not pick time of the day, and do not have a tripod. If that is how you always shoot and you absolutely need F5.6 or more all the time, then you probably should not buy Full Frame for its IQ advantage.

Final word

This post does not seek to prove that Full Frame is the right choice for everyone, this point must be made clear. Rather it is addressing some of the myths/misinformation floating around that tries to dissuade people from stepping up to Full Frame. Photography for us, the hobbyists, is that just that, a hobby. We derive pleasure from generating better looking pictures. People in this forum often ask about whether they should buy Full Frame cameras in pursuit of better image quality. The short and simple answer is yes, provided he is more competent than a complete novice Full Frame will produce better looking images.

Canon EOS 60D Canon EOS 6D Nikon D610 Nikon D7000 Nikon D7100 Nikon D800 Sony Alpha NEX-5 Sony Alpha NEX-7
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