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I recently upgraded from a 350d to a 5d mark ii

One thing I noticed is that I seem to be able to use slower shutter speeds with the bigger camera. (On the order of decently sharp pictures at 1/20 55mm) where on the 350d i strugled with (1/30 at 55mm).

Could the weight of the setup have anything to do with this? (I’m using the 5d mark ii with the wft-e4 wireless transmitter that add similar weight to a battery gripp)

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The following presumes the assumption stated in the question: the same focal length of 55mm is being used for both cameras.

There are several factors that could be at work here:

  • With a larger sensor and the same focal length, it takes larger camera movements to move a point on the image projected by the lens that corresponds to a point in the scene the same percentage of the sensor width and height. This means that if images from both cameras are viewed at the same size, the blur from the same amount of movement will look smaller in the image from the camera with the larger sensor.
  • With a heavier camera body it takes more force to overcome inertia and move the camera the same amount of angular, rotational, or lateral distance. The EOS 5D Mark II body weighs 32 ounces and the WFT-E4 adds another 13 ounces to it, the EOS Rebel XS/350D weighs 17 ounces.
  • If different 55mm lenses are used with each camera, a FF lens tends to be heavier than an "equivalent" APS-C lens. The Canon EF 24-70mm f/2.8 L weighs 32 ounces, the EF-S 17-55mm f/2.8 IS weighs 23 ounces. (The lighter EF-S lens includes IS. The heavier FF lens does not! Otherwise, the difference in weight would be even greater.)
  • Add the cameras and lenses above together and the FF combo is 77 ounces (a whopping 4.75+ pounds!) compared to 40 ounces (2.5 pounds).
  • On the other hand, if the camera is heavy and you hold it up for too long, your muscles could become fatigued and the heavier weight would eventually result in you being less stable as you hold the camera. If it is extremely heavy you may struggle to hold a very heavy camera/lens combination steady for any length of time.
  • Since the pixel width of the APS-C 8 MP EOS Rebel XT/350D and the FF 21 MP EOS 5D Mark II are both 6.4µm, at 100% viewing (one image pixel per screen pixel) there should be no difference in the amount of blur caused by the same amount of camera movement when both are enlarged by the same amount. (Remember, when both are enlarged by the same amount the image from the FF camera covers over twice the total area compared to the APS-C camera).
  • If you are using different 55mm lenses on each camera and one or both incorporates Image Stabilization, one lens may outperform the other in this regard. Given the same generation of technology, the more expensive FF lenses will usually give slightly better IS performance than their APS-C counterparts.

In all of these cases except one, these factors favor the larger, heavier camera with a larger sensor and a heavier, more expensive lens. In the case of the exception, there is no difference either way.

  • In my example the same 55-200 lens was used on both cameras. I was mainly interested in how your point 2 about inertia. What does conventional wisdom say about how pronounced the effect of inertia (or some other property of weight such as the psycological effect indicated in another answer) is to stabilize a handheld camera? Can twice the weight really help stabilize with half a stop to a stop in shutterspeed? (Trying to discount the effect of point one about angle of view, I the question the 1/20 vs 1/30 shutterspeed was getting at that). – lijat Oct 29 '18 at 5:12
  • @lijat It all compounds together. Even with the same lens, everything else applies (and please remember that answers should be written in a way that will be useful to others who might also have the same question - your question did not specify the same lens, only the same focal length). A 5° angular shift in the camera position will create 1.6X more blur with an APS-C camera than with a FF camera if the images from both cameras with a 55mm lens are viewed at the same display size. – Michael C Oct 29 '18 at 5:18
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    Inertia of a more massive body at rest (with respect to the frame of reference) means it takes more force to move it with the same amount of acceleration than a body with less mass. The same amount of force will result in less acceleration and thus less total movement over the same time period. – Michael C Oct 29 '18 at 5:20
  • @lijat The other answer does not suggest a psychological effect. It discusses the physiological effect of supporting a heavier object. – Michael C Oct 29 '18 at 5:27
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    An object with twice the mass requires twice the force to accelerate it at the same rate as another object with half the mass. The same amount of force would accelerate an object with twice the mass half as far in the same amount of time. One stop is twice the shutter time... – Michael C Oct 29 '18 at 5:30
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You are able to use slower shutter speeds because you switched to a larger sensor. A given amount of movement is relatively smaller compared with a larger sensor than a smaller one, proportional to the crop factor. The type or cause of the movement does not matter (angular, linear, rotational, whatever). The 1/20 sec vs 1/30 sec speeds you mention corresponds with switching from a 1.5-1.6 crop sensor to full frame.

Weight does not seem to play a significant role in your case because, if it did, you would be able to use shutter speeds slower than crop factor alone could account for. In principle, increased weight could stabilize against movement by providing resistance against external forces (inertia), but it can also worsen camera shake by requiring greater muscle engagement, which would increase essential tremor.

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    the sensor size is irrelevant because the camera captures angles, not locations. in other words: what matters is angular position in the field of view, not the absolute position. the same shake produces identical blur in a smartphone and in a large format camera (it is obviously easier to shake a smartphone, though) – szulat Oct 28 '18 at 11:47
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    @szulat That depends on how you check sharpness. If you check on a certain print size, the sensor size does matter, you have to multiply the focal length with the crop factor. If you check on a screen, at 100% magnification (or any fixed percentage) then only the pixel size matters. – Orbit Oct 28 '18 at 14:04
  • Pixels and camera sensors do not exist - I compare just the idealized image seen by the camera because there is no reason to include misleading technical details into the picture when talking about motion blur differences between cameras. Obviously this assumes comparing different cameras but equivalent pictures, otherwise the comparison is pointless. – szulat Oct 28 '18 at 17:06
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    @szulat "the same shake produces identical blur" – Only if you change the focal length of the lens to cover the same field of view. If the focal length is kept constant, as in this case (55mm), changing sensor size changes the relative size of movements and the amount of blur that is captured. – xiota Oct 28 '18 at 23:18
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Beside the effect from full frame sensor (bigger photo cells) there is physiological effect. Your mind command muscles to hold strongly the camera because of the weight (bigger for full frame camera). Same is true when you add accessories to the camera line battery grip or heavier lens. But this effect have limitations in sense of the force and how long this force can be applied by particular person.

  • The 350D and 5D Mark II actually have the same pixel pitch: 6.4µm. The former has 8 million of them, the latter has 21 million of them. – Michael C Oct 29 '18 at 2:59
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    Also, a lot of unwanted camera movement appears to be from the actuating force of the actual release button... a heavy camera dampens that... – rackandboneman Oct 29 '18 at 21:26
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The weight may have to do. The shutter has to accelerate quite brutally at the top, and gets rapidly stopped at the bottom. Both create impulses on the camery. Heavier cameras distribute the impulses better. Given that shutter mass likely does NOT increase similar to camera mass, it is one possible explanation. Never thought about it before, though.

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I see a lot of strange assumptions here. The main strange assumption appears to be that a larger sensor will help against shake. But that is only relevant if the displacement of the sensor is a significant factor for motion blur. This may be the case for macro photography or closeup photography. However, the camera is not held at its center of gravity and both hands will have significantly uncorrelated shake. That means that the resulting rotations will become much more relevant once the object distance is not dwarved by the focal length.

Now with a bigger camera you have several effects: overall mass will be larger, meaning that equal forces lead to smaller displacements. Overall size will be larger, meaning that equal displacement difference between the hands will lead to smaller angles of rotation. Putting this together, rotational inertia will be larger. Rotational inertia, the ratio between angular force and resulting angular momentum change, grows with the square of the distance to the rotational centre and the weight (of course leverage also grows with the distance, but only linearly).

Now there also is motion compensation with modern cameras, using lens movements and/or sensor movements. When smaller angles need to get compensated, this kind of compensation has more room to go before it has to give up.

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    Unless image stabilization technology is involved, moving the camera = moving the sensor = sensor displacement. If the sensor didn't move while hand-holding the camera, there would be no need for tripods and image stabilization technologies. – xiota Oct 30 '18 at 0:14
  • You also assume that 1. both hands are on the camera body, but the most commonly recommended grip involves supporting the lens with one hand; 2. both hands move in opposite directions by the same amount, which they usually don't; 3. the sensor is centered in the camera body, which it usually isn't; 4. heavier cameras are significantly wider than lighter ones, which they aren't, for practical reasons. – xiota Oct 30 '18 at 1:08

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