ken.berry wrote:
Both 16MP bodies but different sensor sizes.
The greater the crop factor the greater the magnification. And the higher the MP count the greater the magnification when viewed at 100% on a computer monitor. If you understand why a longer focal length requires a higher shutter speed to get a clear shot, then you understand this because it's basically the same thing. The more you magnify the greater the impact of even small movements.
Yes, but that's irrelevant assuming you're assessing the sharpness of a point that's actually in focus, is it not? We're talking about motion blur here, whether it's motion of the subject or motion of the camera.
And in fact, speaking of motion, I believe we're really talking only about motion of the camera, not of the subject. If I were to decide, for example, that 1/400-1/500 is the minimum shutter speed I need to reasonably stop motion in most sports (as I have), I don't think that changes based on pixel density, even if I'm enlarging more. The subject's relative motion within the time the shutter is open isn't changing, and the fact that I might be enlarging it more doesn't matter. But the camera's motion is magnified when I enlarge, so if I'm going to be using say 1/8 of a frame now in some cases instead of 1/4 of a frame, I'm probably going to have to bump that personal minimum up a step or two — regardless of whether my subject is in motion or not.
Mind you, I'm looking at this in the context not of the sort of nature and wildlife photography where I might have the luxury of very painstaking long lens technique — sandbags, remote release, mirror lockup and all — but sports where it's generally all I can do to get the focus point on the subject before I shoot, with the rig on a monopod where it's prey to a lot of motion on all axes save one. BIF is no doubt very similar.
This is some great conversation and one of the reasons I really like this board. I think the greater motion blur on higher resolution sensors is why it is important for the camera manufacturers to continually improve higher ISO performance in compensation. This will keep the balance between shutter speed and pixel sharpness in check and similar to the film standard of 1/focal length somewhat still effective. It will be nice when the high ISO performance is improved so this standard is surpassed, but as long as it is not going the other way I am happy.
Yes - you only need a higher shutter speed if you actually want a sharper picture than you were getting with your lower rez camera. Pixel density has no effect on the extent to which shake blurs a print. Increasing the pitch affects per pixel motion blur, not per picture motion blur.
it doesn't matter whether the camera is sweeping past the subject or the subject is sweeping past the camera. If the net effect is that the subject is blurred on the sensor plane then it will be blurred. Suppose the blur was 1% of the width of the sensor, regardless of how caused. On a 30D the blur would be 35 pixels wide. On a 50D the blur would be 48 pixels wide. On a 7D the blur would be 52 pixels wide. If you were to view the files at 100% the blur would appear larger from the 7D.
If you wanted to reduce that blur to 0.1% of the sensor width you'd need to increase the shutter speed tenfold. Even then, the 30D would show a blur width of only 3.5 pixels, whereas the 7D would be showing a blur of 5.2 pixels. In order to make the blur look identical at 100% viewing you'd need to shoot the 7D image with a shutter speed that was faster by a factor of 5184/3504 = 1.48X, or about 50% faster.
How do you achieve that extra shutter speed? Well, obviously you have to add light, open up the aperture or increase the ISO. This is why one must be very cautious, and realistic, when it comes to believing that a 7D offers more cropability compared to older generation cameras. For slow subjects/scenes shot in good light from a stable platform that is almost certainly true. For active subjects in poor light or with a handheld, unstabilised, long lens, that may well not be true. If the blur/shake doesn't get you then the per pixel noise might.
Of course, that doesn't even begin to tackle other issues such as lens sharpness, focus accuracy or reduced DOF at greater levels of enlargement.
The issue of pixel density and shutter speed is, I think, related to one very simple concept. The more you are enlarging a file, the more you are also magnifying motion blur (or camera shake). If you compare, say, a 1D Mark II with 8 mp to a 1D Mark IV with 16 mp and if your intention is to be able to crop to the same extent or to print to the same size with both cameras, then the required shutter speed to eliminate motion blur (or camera shake) with either camera is still going to be the same.
If, on the other hand, you want to use the extra pixels on the 1D Mark IV to be able to crop to a greater extent or to print larger, that means that you will be enlarging the file more. When you enlarge the file more, you are also magnifying motion blur (and camera shake), and faster shutter speeds will help to reduce the effects of the increased magnification.
So, the bottom line is that, you aren't going to be any worse off with the camera with a higher pixel count. Printing to the same size or cropping to the same extent with two cameras with the same crop factor and different numbers of pixels should require the same shutter speeds for the same sized print or the same amount of cropping. However, the advantage of the camera with more pixels is that it gives you the ability to print larger or crop more, but doing so, because it requires enlarging the file more, might require faster shutter speeds to avoid the effects of magnifying motion blur (or camera shake).
uz2work wrote:
The issue of pixel density and shutter speed is, I think, related to one very simple concept. The more you are enlarging a file, the more you are also magnifying motion blur (or camera shake). If you compare, say, a 1D Mark II with 8 mp to a 1D Mark IV with 16 mp and if your intention is to be able to crop to the same extent or to print to the same size with both cameras, then the required shutter speed to eliminate motion blur (or camera shake) with either camera is still going to be the same.
If, on the other hand, you want to use the extra pixels on the 1D Mark IV to be able to crop to a greater extent or to print larger, that means that you will be enlarging the file more. When you enlarge the file more, you are also magnifying motion blur (and camera shake), and faster shutter speeds will help to reduce the effects of the increased magnification.
So, the bottom line is that, you aren't going to be any worse off with the camera with a higher pixel count. Printing to the same size or cropping to the same extent with two cameras with the same crop factor and different numbers of pixels should require the same shutter speeds for the same sized print or the same amount of cropping. However, the advantage of the camera with more pixels is that it gives you the ability to print larger or crop more, but doing so, because it requires enlarging the file more, might require faster shutter speeds to avoid the effects of magnifying motion blur (or camera shake). ...Show more →
This is another one of those misunderstandings of how things work that is in the same category as the notion that you must avoid small apertures on cameras with higher photosite density because of a different "diffraction limited" aperture. It also continues because people don't understand how digital sensors and binary representation of data work.
Here is a though experiment. Take two cameras that are otherwise functionally identical for our purposes but which have different photosite densities - the 12MP 5D and the 21MP 5D2 would work for the example. Put a nice sharp lens on the 5D - let's say a stopped down EF 50mm f/1.4 - and make a series of hand held photographs at whatever shutter speed seems like a good one for the comparison. Now switch the lens to the 5D2 and use the same aperture and shutter speeds and make a similar sequence of hand held shots of the same subjects. Take both sets of images through a normal workflow and make nice large prints - let's say 16" x 24" - and offer the prints to an impartial observer and ask them to place the images into two piles: the "sharper" pile and the "less sharp" pile. (Or save time and make the comparison yourself.) While it _might_ be possible to see other differences between teh images (e.g. - not motion blur-related sharpness) there will be, on average, exactly the same amount of motion blur in both sets of images.
To the extent that camera motion is the limiting factor in terms of the sharpness of your images, there will be exactly the same effect in both cases.
Dan
Nill Toulme wrote:
This new review of the Mark IV served to remind me of a question that's been puzzling me, which is that of purportedly needing higher shutter speeds to avoid motion blur as we move to higher resolution cameras. I've seen this mentioned any number of places, including Canon's Mark IV white paper.
This review puts it this way:
The high pixel density of the 1DmkIV has two negative implications - it puts great demands on lens quality and also the camera is more susceptible to camera shake/motion blur. I find that I have to raise my shutterspeed a little to ensure getting a sharp image on the mkIV. To give you an idea of this, I took some images with the three cameras (plus 500mm f4 on a tripod trained on a distant target) reducing the shutterspeed progressively until the results were no longer critically sharp when viewed at 100%. I found that I could get away with 1/30th sec on the 1DsmkII, 1/80th sec on the 1DmkIII and 1/125th on the 1DmkIV. This is quite significant and would necessitate increasing the ISO setting over the other cameras by up to 2 stops in low light conditions to compensate.
The key seems to me to be the "viewed at 100%" part. Isn't this nothing more nor less than a matter of greater magnification? A Mark IV file viewed at 100% on a given monitor will be magnified to a greater degree than will a Mark III file — kind of like looking at an 11x14 print instead of an 8x10. And we all know that the larger you blow up your files, the more critical each of the various components that go into "sharpness" — lens quality, precision of focus, camera motion, subject motion, etc. — becomes. So yes, if we're going to magnify our images to a greater degree, then we have to be more careful about these things.
But the fact is, aside from when we're pixel-peeping at 100%, we're not (necessarily) going to be enlarging our images any more than we are already. Just because we can doesn't mean we will — I don't think I'll start selling less 5x7's and more 8x10's just because I bought a Mark IV, nice as that would be.
Put another way — and here's where the "Am I missing something?" part comes in — does "pixel level sharpness" have anything to do with overall perceived image sharpness when we're viewing the image not at the pixel level, but at "normal" print or onscreen viewing sizes? IOW — do I really need to bump up my shutter speeds if I only care what my images look like at those magnifications, not at 100%?
What makes me think I'm missing something is the difference in his findings between the 1DsMkII and the MkIV — both 16MP bodies. I don't understand how the difference in crop factor alone could lead to that much of a difference — two stops worth! — in perception of motion blur.
tdodd wrote:
it doesn't matter whether the camera is sweeping past the subject or the subject is sweeping past the camera. If the net effect is that the subject is blurred on the sensor plane then it will be blurred. Suppose the blur was 1% of the width of the sensor, regardless of how caused. On a 30D the blur would be 35 pixels wide. On a 50D the blur would be 48 pixels wide. On a 7D the blur would be 52 pixels wide. If you were to view the files at 100% the blur would appear larger from the 7D.
Argh... I really need to get some shoots processed, but one more...
I think it does matter. Here's why (and let's see if I can state it clearly on a Saturday morning — I'm not sure I can).
A given amount of camera motion is always the same relative to the frame. If I bump the lens 1/8" while the shutter is open, it is what it is, and if I enlarge more, I'm magnifiying that flaw by a proportionate amount.
But a given amount of subject motion is not always the same relative to the frame, because the subject may be closer to or farther from the camera. If I fill the frame with a soccer player running full speed, she might move two inches during the 1/500 second the shutter is open, and that's (let's pretend, without doing the math) 2% of the width of the frame. But if that same player is farther away, and I only fill 1/4 of the frame, then that same two inches is only 1% of the width of the frame. If I blow it up to the same print size as the first one, I'm back to 2%, and the amount of perceivable motion blur caused by subject motion is exactly the same, neither better nor worse. On the other hand, the motion blur caused by camera movement has now been doubled.
Yes, I do understand what you are saying, I don't think that is relevant. You're arbitrarily changing a variable there that should not be changed for the purposes of this discussion.
Take the example of shooting a bird in flight with a handheld, unstablised 400mm lens. Let's say I've done my maths and choose to shoot at a shutter speed of 1/2500 in order to make camera shake negligible even when viewing a 7D file at 100%. That's all fine and dandy, but what about wing blur? Even at such shutter speeds it is quite possible to see blur at the wing tips. Let's say that the blur is 10 pixels wide as captured by my 7D. If I was to shoot the identical image with my 30D, same shutter speed and everything else, the wing blur would only extend to about 7 pixels wide.
Now, if your subject is moving slowly enough that the subject motion blur is inconsequential, relative to the blur from shake, then that's fair enough, but the fact is that in order to determine a suitable shutter speed for a shot you need to take account of camera shake, subject motion blur and final enlargement factor. None are irrelevant.
I don't understand ... what variable did I change? Yes I did posit that I might be enlarging a subject that's farther away from the camera to a larger degree... but that's precisely what we are discussing (I think). I.e., more pixels means more cropping ability (all else equal), which means I might (and in fact will) now be selling prints taken from 1/8 or even maybe 1/16 of a frame, which I probably would not have done with a Mark II image.
Or are you back to talking about "pixel level blur?"
You're moving your subject to a greater distance in order to reduce the blur as a % of the sensor width. But what has that to do with anything. You might equally well say that your subject reduces its speed by 50%, with the same effect. But so what? I might say, but what if you only jarred the camera by 1/16"? That doesn't change anything as far as the ability of a high density sensor is concerned vs a low density sensor when it comes to resolving the amount of blur.
The fact is that you need a shutter speed fast enough to deal with both shake and subject motion. It might turn out that the subject motion is more of a concern than the shake. It might not.
Yes but... I think we've agreed that we will only need higher shutter speeds due to higher resolution to the extent the higher resolution is causing us (allowing us) to enlarge more. Yes? (See Dan's "thought experiment" above.")
You're moving your subject to a greater distance in order to reduce the blur as a % of the sensor width. But what has that to do with anything.
I'm not "moving my subject." It's rather that I now have the luxury of selling prints of subjects that fill a smaller portion of the frame, because the greater resolution allows me to enlarge more. Those subjects' motion relative to the frame is reduced, because they're farther away.
Somebody help me out here. I knew I wasn't stating the case well.
And that means that while I might need some additional shutter speed to make up for my now-magnified sloppy camera handling, I don't need any additional shutter speed with regard to subject motion. Yes?
That still depends on which motion is the more limiting factor - that of the camera or that of the subject.
It also depends on whether your shutter speed was fast enough in the first place to still serve you well at the new level of enlargement.
If you use a tripod, monopod, IS, or have incredibly steady hands, or shoot with short focal lengths, then the subject motion might be the more significant element for which movement needs to be controlled. Then again, if you're waving a Bigma around at 500mm with no support at all, and are on a caffeine high and have just climbed a hill, only to shoot racing snails, then camera shake will probably be of more concern.
Fair enough... but remember I stated as a given that I had determined my shutter speed was adequate for stopping subject motion. That leaves only camera motion to worry about when I'm enlarging a smaller section of the frame. No?
WAIT! Before you crank up that ISO! Hi-ISO noise also degrades the image as well as motion blur. Yes you may have a larger file with more pixels on the sensor, with corresponding smaller pixel edges, but you can often get the same resolution and pixel edges by upsizing the file in PP from a sensor populated with less pixels.
The dirty little secret is that, especially for 16/18Mp crop sensors (and the anticipated 30Mp+ 1Ds Mk IV), you need ideal conditions, slow/medium ISOs, fast shutter speeds, sturdy tripod/mount, the best IQ lenses and most often mirror lock-up to realize the ultimate resolution of these systems.
This is why I bought the D3s for my low light work and will not be buying the crop sensor Mk IV. The FF Nikon offers a better blend of features due to more Sensor Real Estate. If I really want more, daylight resolution I step up to 21+ Mp FF Canons or, for in-animates, stitch.
NIll, I think it is time to go process those shoots. ;-) (Partly because I want your thoughts on using C1.)
This has been a good discussion. Both for the practical implications of the changing technology and for the fact that it helps people like me revisit our expectations. And for those whose technique is honed to near-perfection, which is the case with most of you who own Mark IVs as you are likely pros, the camera differences are now significant. And I love the tech talk though some of it is currently beyond me which is cool 'cause that means I have more to learn.
My challenge is more in line with what Mark said (and Ron implied) early on in the discussion. That in essence new technology is exposing areas in our technique which could use improvement. The greater pixel density when "magnified" through cropping and/or enlargement is exposing more blur from camera shake as it will expose lack of resolution from mediocre lenses. Another way of saying it is that in the days of less pixel density it was hiding my weaknesses. Now, like Mark pointed out, I need to improve rather than relying on higher shutter speeds to compensate for my poor technique. (Nill, I always had a difficult time with how you could shoot soccer at 1/320 or 1/400. It was simply because your technique is much better than mine!)
If I don't crop any more than I used to and if I don't enlarge any more than I used to them I'm OK. But IF I work on my technique then I have an opportunity to get a lot more quality shots and to do a lot more with them. In other words, I can grow into the amazing capabilities of this camera.
(First shoot with Mark IV and first time with 300 2.8 and all on a poorly lit field. I'm afraid to look.)
