Why are full frame DSLRs so much bigger

Than their film counterparts?

My Canon XT is about the same size as the Rebel SLR we bought back in 2000. (though the film cam is heavier)

Point and Shoots can have 12mp, but are teeny compared with their compact film counterparts

35mm is still 35mm whether it's film or digital. So what else is under the hood that turns a simple camera into a tank?
http://www.cheesebuerger.de/images/s...onfus/c010.gif

Sensors on point and shoots are *significantly* smaller than sensors on SLRs. developing the silicon wafers to create the full frame sensors is a lot more expensive, plus everything about the full frame cameras is built to the highest standards. Hold a full frame DSLR and the Canon XT feels like a toy in comparison, polycarbonate/magnesium alloy casing vs plastic. A lot more R&D goes into them, a lot more engineering, etc. There is also *way more* under the hood of an DSLR than an film SLR.

Sensors on point and shoots are smaller than your baby toe nail, the APS sensors have a 1.5x crop factor, but most point and shoots have about a 5-7x crop factor (field of view).

The main reasons are - speed and power and viewfinder and sensor size. Because Full Frame DSLRs are built for professionals, it needs to deliver speed of operation. The fact that the sensor electronics are larger, and need to operate at high shooting rates, means that the power supply needs to be more robust to deliver lots of power in high current bursts that are more substantial than in a smaller sensor camera that shoots at slower frame rates. So the entire power supply portion of a full frame DSLR tends to be bigger than a smaller-sensor SLR. Similarly, a small sensor SLR has the same issues compared to a compact point and shoot. This is not pixel count, it's the physical size and number of transistors of the sensor electronics that drives this.

And finally, the viewfinder has to be larger, to cover the wider frame, without losing brightness. Because these viewfinders need to be high quality, they use a pentaprism, which is a big chunk of optical glass, the same as what's in a pro-level 35mm film SLR like a Canon F-1n or Nikon F5. Also, the mirror box and shutter mechanism must be larger to cover the larger sensor than in a smaller sensor DSLR.

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Originally Posted by Dougjgreen

The main reasons are - speed and power and viewfinder and sensor size. Because Full Frame DSLRs are built for professionals, it needs to deliver speed of operation. The fact that the sensor electronics are larger, and need to operate at high shooting rates, means that the power supply needs to be more robust to deliver lots of power in high current bursts that are more substantial than in a smaller sensor camera that shoots at slower frame rates. So the entire power supply portion of a full frame DSLR tends to be bigger than a smaller-sensor SLR. Similarly, a small sensor SLR has the same issues compared to a compact point and shoot. This is not pixel count, it's the physical size and number of transistors of the sensor electronics that drives this.

And finally, the viewfinder has to be larger, to cover the wider frame, without losing brightness. Because these viewfinders need to be high quality, they use a pentaprism, which is a big chunk of optical glass, the same as what's in a pro-level 35mm film SLR like a Canon F-1n or Nikon F5. Also, the mirror box and shutter mechanism must be larger to cover the larger sensor than in a smaller sensor DSLR.

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Ok, that makes sense. I didn't consider the power pack and the physical scope of the electronics.

Yet I'm not clear on the difference with regard to the prism and shutter mechanism; wouldn't these be of equal size in a full frame DSLR to its film counterpart? Since I don't know the F-1n or F5 you'll have to humour me by explaining how these are different from a "regular" 35mm SLR.

@Anbesol - thanks for your summary about sensor size. I probably should have explained that I was making an example of how the technology has decreased the size of compact cameras, whereas with DLSRs, the reverse is true.

Ta,

Doug is right - it's about power and features. If you look at the Canon EOS 1V - their last pro film body, it's exactly the same size as the EOS-1Ds bodies - and they're huge. Besides the stuff that Doug listed - viewfinder size, power, etc. - pro bodies are also built stronger and often with some level of weatherproofing. You could pound nails with an EOS 1D or EOS 1V camera body. You definitely wouldn't want to try that with a Rebel, though :D

My strap broke and I dropped my 1DSmkII gently (more slid than dropped) from my shoulder to carpet. Seems to still be working fine. I wouldn't use it to drive nails, but I'm glad it's tougher than nails !

Thanks all for your informative replies. I have a better understanding of camera types now. I assumed 35mm SLRs were the pinnacle of portable gear (lenses notwithstanding) and believed that those "monsters" at the camera shop were large-format cameras. In thinking "full frame", I was only considering frame size, not the housing and features/functions.

I can now better appreciate that full frame DSLRs are the equivalent of the professional cameras designed for specific applications and image making, as opposed to mulitpurpose DSLRs.

I still continue to hope, like so many others, that one day "full frame" in digital cameras will be produced in consumer-friendly format - I don't need to hammer nails, nor do I work for National Geographic, but it sure would be nice to get the full field of view from my lenses :smilewinkgrin:

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Originally Posted by Anbesol

Sensors on point and shoots are *significantly* smaller than sensors on SLRs. developing the silicon wafers to create the full frame sensors is a lot more expensive, plus everything about the full frame cameras is built to the highest standards. Hold a full frame DSLR and the Canon XT feels like a toy in comparison, polycarbonate/magnesium alloy casing vs plastic. A lot more R&D goes into them, a lot more engineering, etc. There is also *way more* under the hood of an DSLR than an film SLR.

Sensors on point and shoots are smaller than your baby toe nail, the APS sensors have a 1.5x crop factor, but most point and shoots have about a 5-7x crop factor (field of view).

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I hope that's true cause I'm getting the D700 soon (in october 2009 :p)

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Originally Posted by Cathathome

Than their film counterparts?

My Canon XT is about the same size as the Rebel SLR we bought back in 2000. (though the film cam is heavier).

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You have to compare apples to apples. A rebel is more like a plum when compared to a semi-pro body apple like you are contemplating. Take a look at an EOS 3 and compare it to the equivalent digital, a 5D (well not quite the EOS 3 was a great affordable body with better features). They are quite similar in size. An entry level body like a Rebel doesn't have nearly the features or the build of a semi pro body such as the X or XD bodies.

Not all "full-frame" DSLR's are giants. The D700 and 5D are only a bit bigger than the Rebel, until you add the optional battery pack. I always have mine fitted because of the accessories:

A "full frame" DSLR is expensive therefore bought mostly by professionals. Professional lenses include f2.8 constant zooms which are enormous and heavy. This is a physical necessity - you need a big hole on the front and lots of glass to capture the light.

Big heavy lens means you need a strong metal chassis and lens mount, not a plastic one like the Rebel. Plus I find I need a bigger body just to physically hold onto the thing and keep it steady, especially when I add the cobra flash on the top.