Full Frame vs Crop Sensor

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Canon 5d mk ii
The Canon 5D MK II has a full frame sensor and a recently reduced price tag

The discussion of a full frame DSLR versus a crop sensor (APS-C) camera just got more interesting when B&H Photo decided to offer an eye-popping discount on the Canon 5D MK II, offering the body-only with a 16 GB CF card for under $2,000 around Christmas (now back up to $2500).

While I can live without a full frame sensor, the concepts of “need” and “want” become jumbled at times, like when B&H offers a big discount on a full frame camera that I wanted anyway. So, it’s good to go back over the differences and remember why you select one over the other.

First, it might be good to understand where the term “full frame” comes from in the first place. Full frame means the camera’s image sensor is roughly the same size as 35mm film, or 24mm x 36mm. That, my friends, is a big sensor. And, when it comes to sensors, size matters.

Interestingly, one of the reasons you frequently find a Canon 7D being used on a movie set like Black Swan, instead of a full frame Canon 5D MK II, is because the APS-C chip also approximates a film stock used widely in motion picture production called academy 4-perf. PL movie lenses cover 16mm x 22mm and take a wild guess how big an APS-C sensor is? If you guessed 13.8mm x 20.7mm, you were cheating.

The bottom line is a Canon 7D with a PL mount can accommodate all those marvelous movie lenses. There’s even a place that will permanently alter your 7D to be a PL mount movie camera!

It’s More Than Physical

The physical difference between the sensors is significant, with the full frame sensor being closer to twice as large. That is both good and bad depending on the circumstances. Since big chips are harder to manufacture and have a higher defect rate, they are vastly more expensive. So, if your wallet has anything to say about your camera selection, you’ll likely end up with an APS-C camera.

sensor size
You can see the APS-C chip is slightly less than half the size of a full frame 35mm sensor

The payoff for the extra cost of a full frame sensor is in the detail you get and the low light performance. At ISOs above 1600 a Canon 5D will simply blow the doors off my 7D. Even though I don’t do that much low light shooting, that’s my excuse for wanting a 5D MK II.

Also, if you’re shooting a lot of landscapes or other fine detail, a full frame camera will provide better resolution at distance.

Notice the qualifier “at distance”. Up close, like in a studio setting, the difference will be extremely difficult to notice with the biggest differences introduced by the quality of the lenses.

What Strange Magic Is This?

It’s not magic, just that at studio and portrait distances a full frame camera is shooting largely on the center of the sensor and you’ll likely be cropping out the edges anyway. That’s why I can shoot studio shots side-by-side with my friends owning 5D MK II’s and they’re surprised to see very little difference in our final shots. However, were we to walk across the street to the beach and shoot some landscapes, they would remember why the extra money was worth it.

That’s why it’s important for people to have an idea of what kind of photography they want to do before selecting their gear. Buying the camera before figuring out your photographic specialty is the tail wagging the dog.

My decision to go with a 7D is because most of my work is as a PJ. Lots of run and gun, a lot of being bumped, dumped and jostled, and occasionally working in the elements. An armor-plated crop sensor camera is well suited to that type of work, plus I shoot a lot of video.

I was perfectly happy with my APS-C crop sensor…until B&H put the full frame 5D MK II on sale. Curse you, B&H, curse you. 😉

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