"Motion Blur Experiment on D7000" Tue 25-Dec-12 03:33 AM by Danbie
I while ago there was a post about what settings to use for a D7000 to shoot an indoor basketball game. The author indicated that his photos tended to be a little soft and he shared a few. Truth was that with a little sharpening the photos looked fine for web use and they would probably even make reasonable quality 8x10s. The photographer was using a shutter speed of 1/500s and there was some discussion about whether this was fast enough. My experience is that when shooting basketball from the baseline I try to use a minimum of 1/800s and I push up to 1/1000s when the lighting is reasonable. I find that my photos are sharper when I do this and because I shoot to make and sell large prints (up to 16x24) I want to keep most of the pixels and I want them to be very sharp. Some folks spoke up and said that my technique must be bad because they get good shots at 1/500s. They posted a few shots as evidence but again … I agree that 1/500s is fine for posting a photo on the web but you are losing resolution due to subject motion blur. So I decided to do an experiment. I hung a 6 inch nail with thread to make a pendulum. The total length of the pendulum (to the tip of the nail) is 31 inches. I lift the nail 5 inches above its lowest point and let it swing. Using some math (including second order harmonic corrections) I calculate that the maximum speed at the tip of the nail is about 3.5 mph. I postulate that this speed is a reasonable one to test as the residual motion of the basketball player (even with panning) could easily reach this speed (consider an arm moving or head twisting quickly). Next I set up by D7000 with a nikon f/1.4 50mm lens on a tripod 15 feet away from the nail. I set the focus to manual, quality to raw, f-stop to 2.8. I then vary the shutter speed and iso so that the exposure stays essentially the same (1/250s at iso 100: 1/500s at iso 200, 1/800s at iso 340, 1/1000s at iso 400, and finally 1/2000s at iso 800). The first photo shows the set-up. The rest of the photos are cropped 1:1. Each raw photo was processed in Lightroom 4.2 using the default settings I think the results are clear. If you want the best resolution that a D7000 can provide (given the conditions I used) then a shutter speed of 1/2000sec is best and each shutter speed below that gives a little less sharpness due to subject motion blur. 1/1000sec is not too bad. 1/800 is worse and 1/500 is worse yet. 1/250sec is (of course) terrible. I know you can get great shots at a basketball game with 1/500s from the baseline (especially when they don’t move laterally very quickly). But if your subject has arms moving fast or head turning quickly or there is some other motion that you just can’t stop with good panning, then your shot will not be as sharp as it could be. It might still be fine for an 8x10. But the sharpness of an 16x24 will be adversely affected. I also realize that resolution is not everything about quality. Too much noise can also be detrimental. And sometimes I do shoot at 1/500s because the light is so bad. So it is a balancing act. But the point I want to make is that a setting of 1/500s can easily result in lost resolution due to subject motion blur. It is not simply bad technique.
#2. "RE: Motion Blur Experiment on D7000" In response to Reply # 0
That's an interesting experiment, Dan. And I agree with Dave that 3.5 MPH is not a worst-case scenario.
I think some people tend to make a virtue out of necessity. Since they can't achieve a shutter speed of better than 1/500, why, 1/500 must be just fine! As you point out, making poster-size prints exposes the limitations of even the best modern cameras under gym available-light conditions. Those who don't target that kind of print can afford to accept lesser results.
#3. "RE: Motion Blur Experiment on D7000" In response to Reply # 0
Neat experiment. The 1/2000s images are certainly better in terms of subject clarity. I am not familiar with the earlier thread on this topic.
One thought: Wouldn't 1:1 crops be too harsh of a test for images that will be printed at up to 16x24 inches? 4928 D7000 pixels printed across 24 inches is 200 pixels per printed inch. Your images in this Nikonians post are coming up on my Dell monitor at about 4 x 5 inches in real world size. (They'd be even larger on other monitors as I have a high pixel density monitor). Isn't that a much higher magnification as compared with viewing a 16x24 inch print? And one doesn't usually stand close to a 16x24 inch print to view it.
#4. "RE: Motion Blur Experiment on D7000" In response to Reply # 3
A photographic print is usually printed at 240 dpi or higher. As you point out, for a very large print a lower density may be fine because the viewing distance is expected to be further. Keep in mind, however, that you can't always frame the shot in the camera the way you want it to be cropped for the picture. So you might need to make every pixel count. Also recognize that your monitor is about 75 dpi which is much lower resolution than what you would want on a print. I usually try to print with at least 150dpi in the original print, even when printing at 16x24. Note that the printer software will resample so that more dots are being printed than what you have in the picture - but your resolution is still limited by the number pixels you have in the cropped file to print.
#5. "RE: Motion Blur Experiment on D7000" In response to Reply # 4
>Also recognize that your monitor is about 75 dpi which is much >lower resolution than what you would want on a print.
That's my point (if I have this right): The image magnification on a monitor is much higher than on a print. This might lead the viewer to seek motion-stopping shutter speeds which are unnecessarily high.
#6. "RE: Motion Blur Experiment on D7000" In response to Reply # 0
Tallahassee, Florida, US
Thanks for posting this. Neat experiment! Part of the result depends on how close the camera is to the action, though. The nail is moving 3.5mph, but it is only 15 feet away from the camera. If it were further away, it would pass through a smaller amount of the frame, so there would be less apparent motion to the camera from that motion of 3.5mph, so less blur. Of course, basketball players are moving much faster than 3.5mph, so your point is well-taken.
#7. "RE: Motion Blur Experiment on D7000" In response to Reply # 6
I agree that distance, magnification, and sensor pixel densities are important factors. I think that 15 feet is very reasonable median distance when shooting basketball on the baseline with a D7000 and a 50mm lens (if you are much further away you will need to crop the photo to get the action between just a few players). The sensor pixel density is highest on the D7000 and the D800 (basically same pixel densities). For cameras like the D700 or D3, the sensor pixel densities are much lower and so you can shoot with a slower shutter speed without sacrificing resolution from what the camera can deliver.
#8. "RE: Motion Blur Experiment on D7000" In response to Reply # 5
Letchworth Garden City, GB
An interesting experiment. I am going on Safari in a couple of weeks and while taking some test setup shots using my dog in motion I have found that my shutter speed is way too slow and a speed between 1/1000 & 1/1500 gives sharper results (obviously) even at the cost of a higher ISO , sometimes up to 1600. One small point is that I believe 75 dpi is the screen resolution on Apple monitors and PC monitors are 96 dpi.
#9. "RE: Motion Blur Experiment on D7000" In response to Reply # 7
I don't think the pixel density really enters into it much. The issue is the amount of motion of the object as a percentage of the size of the final output image (print). Whether the image was captured on a 16-MP camera or a 12-MP camera, if the object (nail, player) moves far enough while the shutter is open to make a discernible blur on the image, the camera will capture and reproduce that blur. At some really low pixel density the motion blur would get lost in the sensor resolution, but that would be at much lower resolutions than any modern DSLR provides.
If your 3.5 MPH speed calculation is correct, that means the nail in your experiment moves about a tenth of an inch in 1/500 second. (Which looks about right from viewing your images.) Your frame is about 30 inches wide at the subject distance, so that 0.1-inch motion represents about 0.33% of the width of the frame.
If the width of the print is 16 inches, that 0.33% means the size of the blur will be about 1/20 inch. Small, but not invisible. Enough to take away a bit of crispness.
As for sensor resolution, 0.33% of the width of a D700/D3 12-MP sensor is over 9 pixels on the short dimension of the frame (i.e., portrait orientation), so those sensors are easily capable of resolving that motion. (I assume you would be using a lens that gives the same FOV on FX.) 0.33% is over 6 pixels even on a D70 and over 5 pixels on a D2H, still quite enough to be resolved. So your point that 1/500 is marginal for motion-stop basketball shooting with large prints remains true regardless of which body is in use.
#10. "RE: Motion Blur Experiment on D7000" In response to Reply # 8
>One small point is that I believe 75 dpi is the screen >resolution on Apple monitors and PC monitors are 96 dpi.
I don't think that makes sense. Screen resolution is a function of the monitor, not the computer. My Dell U2711 has a pixel pitch of 233 microns (whether or not connected to a computer). That's because it was manufactured with 2560 x 1440 pixels across an area with a diagonal of 27". When I use the monitor in its native mode (as I usually do, WQHD, or 2560 x 1440) and view a photograph at 100%, I am getting 109 pixels across every inch of screen.
Going back to the OP's topic (a great one!), when I view his images they are possibly of different physical size than when someone else views them on their computer. That means we are each seeing a different magnification as compared with real life, which then means we are looking at different data to interpret whether some motion blur is significant. Jon, in a later post in this thread, has it exactly right in my view: we need to consider the amount of blur per printed inch when viewing the print at a usual distance.
#11. "RE: Motion Blur Experiment on D7000" In response to Reply # 9
Good points Jon
I was assuming the same fixed prime lens shooting the same subject at the same distance. Of course when using an FX sensor, it would make sense to use a different lens (or magnification) and then the end result is only dependent on the number of pixels available on the sensor. The D7000 still has more pixels than the D700 or D3, but the difference is much smaller. So over-all the key question becomes how many pixels are there in the cropped image and how sharp is the photo (at the pixel level). And of course, pixel density, shutter speed, and subject motion are important factors.
#12. "RE: Motion Blur Experiment on D7000" In response to Reply # 11
>And of course, pixel density, shutter speed, and subject >motion are important factors.
I don't think pixel density comes into it. If you are viewing a same-size print from the whole of the image, it's the distance the subject moves as a proportion of the image width in the time the shutter is open - as Jon has pointed out
#13. "RE: Motion Blur Experiment on D7000" In response to Reply # 12 Wed 26-Dec-12 09:31 PM by Danbie
Hi Brian, Your point is true for the conditions you set (using the whole frame). But using a prime lens to shoot sports means that most photos will have to be cropped. To provide the greatest latitude for cropping and still allowing a large high quality print, you want the best resolution that can be obtained from the equipment you have. This is my point – I can’t think about what is the minimum number of resolved pixels I need but rather I think about how many I can get from the equipment I have. The optimal shutter speed to limit motion blur then becomes pixel density dependent (along with several other factors including focal distance and the subject’s transverse speed). And for my shooting conditions, I find that 1/800s is better and 1/1000s is best when I have enough light.
A completely different mindset is to shoot for a purpose such as the web or maybe a small or medium sized print. At that point, I agree that if you optimize for minimal motion blur at the pixel level then you might be optimizing the wrong variable because most recent DSLR cameras have plenty of pixels to "burn".
Sometimes I do drop to 1/500s when the lighting simply demands it – and in these circumstances I know I simply can’t get high enough quality for a large print due to noise and/or motion blur. Sometimes I’ll bring strobes … but that’s a different story and I have not done that for awhile (here’s a basketball shot with my old D70 using multiple strobes at 1/500s.) I really miss the 1/500s sync speeds.
#14. "RE: Motion Blur Experiment on D7000" In response to Reply # 13
Yes, the optimum shutter speed (in your terms) will vary depending on the degree of crop - because with a deeper crop, any given amount of subject movement will form a larger proportion of the remaining frame width.
If the photographer is more willing/able to crop when using a higher density sensor, then the pixel density does (indirectly) affect the visible degree of motion blur
#15. "RE: Motion Blur Experiment on D7000" In response to Reply # 11
I made the FX assumption just to keep the calculations simple. It doesn't really change the underlying point. While resolution certainly affects image quality at some point it doesn't affect motion blur as long as there is enough pixel density to resolve the blur. My point was that in all cases of Nikon DSLRs given the shooting conditions we are discussing, there is plenty of pixel density to resolve the blur. Thus when we are analyzing the possibility of blur for these conditions we can completely remove the issue of sensor pixel density from the analysis for any extant Nikon DSLR -- DX or FX.
The only issues that matter for motion blur are: how fast is the shutter, how fast is the subject moving relative to the frame. The frame can be the whole sensor or, if you crop, the cropped frame.
Of course, you could crop down to the point where the number of pixels spanning the motion blur were so few that you wouldn't be able to distinguish the motion blur, but at the 1/500 shutter we are talking about your image at that point would be all but unusable due to lack of resolution anyway.
#16. "RE: Motion Blur Experiment on D7000" In response to Reply # 14
>Yes, the optimum shutter speed (in your terms) will vary >depending on the degree of crop - because with a deeper crop, >any given amount of subject movement will form a larger >proportion of the remaining frame width.
Exactly. If you are finding cropped shots to be crisper at higher shutter speeds, it is still motion blur that is the issue, not pixel density. (Of course, that motion blur may come from movement of the subject or from camera shake.)
Look at it this way: If pixel density is insufficient, the whole image will be unsharp, not just the parts in motion.
#19. "RE: Motion Blur Experiment on D7000" In response to Reply # 15 Thu 27-Dec-12 07:04 PM by PAStime
>Of course, you could crop down to the point where the number >of pixels spanning the motion blur were so few that you >wouldn't be able to distinguish the motion blur, but at the >1/500 shutter we are talking about your image at that point >would be all but unusable due to lack of resolution anyway.
What would be interesting would be to repeat the experiment but this time while limiting the cropping to something with enough remaining pixels to enable printing at the desirable print size.
The 1:1 images of the nail in the original post are not a good indicator because one would normally not be cropping that much when making prints. (For web postings it would be reasonable).
#20. "RE: Motion Blur Experiment on D7000" In response to Reply # 16
I think we are "violent" agreement. One of us is looking at the glass half full and the other says the glass is half empty ...
If the pixel density is not sufficient such that you would not detect the motion blur, and motion blur is a significant fraction of the cropped frame, then you can not make a good (large) print anyway because you don't have enough resolution. And in that case, you should optimize for a smaller print. Go ahead and shoot at 1/500s if you want to and realize that you are using the equipment you have to get the best photo you can get. If your equipment is not limited by the number of pixels available in the framed shot, however, then shoot with a higher shutter speed when you can so you get all the info that is available (note that this is affected by pixel density of your camera). So I think we are really saying the same thing ... just looking at from two different directions.
#21. "RE: Motion Blur Experiment on D7000" In response to Reply # 19
The whole point of my post is to try to get all of the resolution that is possible from the shot when you can. I might have a great shot that is nearly full frame of a player shooting a ball while in the air. Later, I might want the large photo to be the entire player showing them two feet up in the air from the floor. In that case a slower shutter speed may be fine. Or I might also have a great facial expression and I want to take a 30% crop - and here I want all the resoultion that is available to maximize my options. So what I want when I'm shooting is to not limit what I can do with the photo later because I threw away resolution due to motion blur. I want to get the most resoultion I can get ... only limited by my equipment. So a 1:1 post is inline with that objective.
In fact, even if you only wanted an 8x10, the amount you can crop to make that 8x10 may be limited by motion blur if you did not optimize for that parameter.
I'm also not saying that it is wrong to optimize for some other situation or purpose. There is no right or wrong here. But if you want to optimize for available resolution, then you need to carefully consider pixel density and shutter speed.
#24. "RE: Motion Blur Experiment on D7000" In response to Reply # 23 Sat 29-Dec-12 06:53 AM by Fabien65
Hi all, Very interesting experiment !. Actually, you are looking for the minimum distance of move that the d7000’s resolution is able to show…and that helps me to understand why D7000 and D800 are more sensitive to motion blur..
In your test settings, if I don’t make any mistake, we can calculate the distance depending of the shutter speed: 1/250 : 6.2 mm 1/500 : 3.1 mm 1/1000 : 1.56 mm 1/100: 0.78 mm