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I am debating if I should upgrade to a full frame camera or not. I heard that full-frame cameras are less forgiving if there is camera shake? My worry is that my pictures might not be as sharp with the full frame if I do not have a lens with image stabilisation. I would like to understand why a full frame would be less forgiving to shake than a smaller APS-C sensor.

I can understand that sensor with higher resolution will be less forgiving to shaking because you can zoom in more on the details but that is a megapixel factor. To make my question more precise, if I had two 15 megapixel cameras and one was a full frame and the other APS-C and if they both had the same 50 mm lens, will there be any difference in sharpness if there is a little shake factor? Will the full-frame camera be less forgiving?

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They're not, unless you are shooting at very wide apertures. –  Michael Clark Apr 18 at 6:08

5 Answers 5

up vote 6 down vote accepted

Rather the contrary.

Pixel density

Of course, as you say, sometimes there is an issue with the sensor - but not directly related with 'more megapixels', but related with the actual pixel density (ie. number of pixels/sensor area). I don't know exactly any more which is the situation right now but it seems that 24 MP APS-C sensors have the biggest pixel density on the market. By tradition, the crop sensors had/have more density than FF ones.

However, the 'pixel density thing' matters when you need 100% (or closer to this) crops. If you want to print at the same size from different sensors then you'll get the same amount of blur, taking in consideration that the 'pixel density' is the only difference between the two systems.

Depth of Field

There are enough places which explain why Depth of Field in the same situation for a FF camera is shallower, and hence you must be more careful to focus (rather than to camera shake) to avoid blur - but take in account that, while this sustain your assertion, this factor can be easily surpassed by the next one.

Shutter speed

The "rule of thumb" for Full Frame is to have the "shutter speed should be at least equal to focal length". That is the minimum shutter speed for a sharp handheld image. So if you have a 400mm lens on the camera then you should shoot no slower than 1/400 sec to get a sharp image.

  1. This rule is normalized to FF 35mm. So if you use a 1.6x crop camera (Canon EF-S), you should multiply 1/f times 1.6. In the above example, it would be 1/400 * 1.6, equaling 1/640th sec. * 1.5 for Nikon DX. * 2 for four/thirds. etc.

  2. This is an old school rule, back when "sharp" meant an 4x6" print that wasn't too blurred. This is way sloppier than modern day view-at-100% pixel peeping standards. (So use an even faster shutter speed if you want the image to be sharp at 100%.) And scale up (faster) if your camera has lots of megapixels.

  3. But contrariwise, the 1/f rule dates from before image stabilization. So you can cut yourself some slack if your camera/lens has image stabilization. (Each "stop" of IS improvement allows for a doubling of shutter speed.)

Hence, this rule of thumb is kind of slip-slidey. But it does give you a place to start from and in practice (I have a little experience with this) FF is more forgiving than a crop one.

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Thanks you for braking down the anwser. I think the depth of field explanation addresses my questions. –  Jerry Apr 22 at 16:29

You get a more shallow depth of field with a full frame camera so if you aren't careful with your forward/backward movements you can throw your subject out of focus. Or if you focus/recompose a lot you may have more problems with that.

That's about all I can think of, though I've never heard someone say that a FF would be more forgiving.

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You have (a little more than) one stop advantage in light sensitivity with FF cameras compared to cropped ones and one stop disadvantage in depth of field. So you might just stop down the aperture 1 stop and increase the ISO 1 stop and you are on-par. Disclaimer: I called 1 stop of disadvantage in depth of field as in regards of this topic.. if you want more subject isolation that's an advantage and arguably it's probably the biggest advantage of FF. –  Marco Mp Apr 18 at 12:22
    
I now better understand that it is not the camera shake (which an up-down-left-right movement) that is the problem, a full frame camera is less forgiving in keeping the focus (which is a further-backwards movement). –  Jerry Apr 22 at 15:47

It's not so much the full frame per se, as the fact that full-frame sensors have 36mp resolution these days, and that people tend to pixel-peep and judge things like sharpness, chromatic aberration, and motion blur at 100% crop (i.e., higher magnification if the resolution is higher).

If, say, you're going from a 12mp camera to a 36mp camera, and you judge things at 100% crop, you're basically using a magnifying glass that's 3x stronger with the higher resolution sensor.

So, yes, a bit of camera shake will look a lot bigger, and be more self evident. At 100% crop. At the whole image level, however, it probably won't.

In addition, full frame sensors will also display the corner performance that was hidden when using a full-frame lens on a crop body. Corners are where the performance of any lens is typically going to be at its weakest--getting light evenly up into the corners is always harder than focusing the light that goes straight through to the center of the sensor. So flaws you may not have seen on a cheapie 50/1.8 on an APS-C body appear when you swap that same lens over onto a full frame body. This is why online boards will teem with comments about how full frame bodies are "more demanding." Well, probably that and the fact that you'll also want to swap out your crop glass if you're dumping your APS-C body in the "upgrade". :)

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What do you mean by "had the same 50 mm lens"? If you used the very same 50 mm lens on a full-frame and APS-C, the effective focal length would be different (50 mm on full-frame, 50x1.6 on APS-C), and higher focal length means more susceptibility to camera shake under the same shooting conditions...,

If you had a full-frame camera with an 50 mm lens for full-frame and an APS-C camera with and APS-C 50 mm lens, then just by similarity of triangles, the same angular shake would create exactly the same blur on both sensors.

The advantage of full-frame cameras is that because of the larger sensor, you can boost your ISO higher without image noise and degradation, so you can use higher shutter speed and ISO with full-frame bodies, and that means less camera shake than with APS-C, if you are going for the same image quality (and noisiness).

(And as a side remark: full-frame bodies and lenses are usually have more mass, so that reduces camera shake proneness as well...)

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You seem to be using "APS" to mean "35mm full-frame", but that's not correct. APS was a film format that allowed a variety of aspect-ratio crops (APS-H, APS-C, APS-P), but they were all smaller than the 24x36mm frame size of 35mm film. en.wikipedia.org/wiki/Advanced_Photo_System –  coneslayer Apr 18 at 12:40
    
@coneslayer: Yes! Sorry. I update my answer... –  TFuto Apr 18 at 12:43
    
@coneslayer: Super comment, by the way! –  TFuto Apr 18 at 12:46

It isn't camera shake that makes them less forgiving, it is depth of field. At any given aperture, your DOF will be much shallower on a FF, so working at wide open apertures will make focusing a real challenge.

I suppose one could make the argument that this translates in to camera shake since to maintain the same depth of field as an APS-c camera, you would have to use a smaller aperture, thus letting in less light and having to use a slower shutter speed or higher ISO and if you kept the ISO fixed, the slower shutter speed would make camera shake more critical, but that's pretty far removed from what the FF size actually causes, so I would never say that a FF makes camera shake a bigger problem.

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