larrylas wrote:
Problem: would like to take two pictures of a motorcycle, One with background blurred the other with motorcycle blurred. SETTING day, cloudy and clear. Got ideas on starting ASA, Shutter speed and aperture?
It depends upon a number of things....
1. How close are you to the action and how long focal length lens are you using?
2. How fast is the subject moving? What direction is the subject moving?
3. Can you use a tripod or at least a monopod?
4. If lens or camera has image stabilization, does it have a panning mode?
You can use a "dragging the shutter" technique with panning motion to photograph the moving motorcycle and cause the background to blur. How slow shutter speed you need to use will depend upon how close you are and how long focal length you're using. You will also find that parts of the subject will be blurred and that a percentage of your shots will turn out as expected, so take lots and lots of extra shots. The slower your shutter speed, very likely the fewer "keepers" you'll get. It's sort of a balancing act trying to find the shutter speed that renders the blur you want, but still captures the subject sharp enough.
You will get different results depending upon the direction the subject is moving. If it's coming directly toward you or directly away from you, you'll see less blurring than if it's moving past you perpendicularly and you are tracking it with a panning movement. If you put camera and lens on a tripod that has a smooth panning movement, you might increase the number of sharp shots. A monopod can work similarly.
Many of the lenses I use have image stabilization. Of those, many have a "panning mode", where the IS only works to counteract movement on the vertical axis. This is so that it's not "working against you" on the horizontal axis. In all honesty, I often forget to switch to panning mode and don't really see a lot of difference when shooting faster moving subjects.
Finally, fill flash can be used to freeze subjects more fully. However, it has to be set to "rear curtain sync" for the movement to appear "correct" behind the subject. If used with normal first curtain sync, the blur effects will be in front of the subject, making it appear to be going backwards.
Below are some examples. All these were done with APS-C crop cameras. Take that into account with respect to the lens focal lengths, in particular:
1. 1/60 shutter speed, 70-200mm lens at 85mm, f/16 aperture. I was quite close to the action and, if I had to guess, the car isn't going much faster than 40 or 50 mph on the straights, a lot slower in the corners. In this first shot, note how parts of the car are blurred, although the driver is sharp...
2. 1/60, 70-200mm lens at 200mm, f/16 aperture. The car is going slower in a corner AND is not moving perpendicular to me, so there's less blurring of the background or foreground objects in this image...
3. 1/800, 300mm lens, f/5.6 aperture. Compare the image below shot at a much faster shutter speed. Notice how all of the car movement is "frozen". Foreground and background blur here is due to depth of field with the longer focal length and larger aperture, instead of being movement blur...
4. For the panned image below I used an even slower 1/40 shutter speed, the same 70-200mm lens as above (at 200mm), f/16 aperture. Notice how both foreground and background are showing motion blur. Incidentally, this was a very fast, highly customized old Triumph Spitfire in all theses shots. If I remember correctly, he won his class and probably top honors for the day...
5. Now at a different event... the vintage races at Laguna Seca Raceway... it was impossible to do panned shots because I had to shoot through a small opening in protective fences. Subjects were going MUCH faster than the above autocross images... probably 70 or 80 mph through the corners and well over 100 mph on the straights. 1/1600 shutter speed, 300mm lens, f/5.6...
6. Here's a panning shot of a considerably slower subject where I used fill flash with rear curtain sync to better freeze the subject movement. 1/30, 24-70mm lens at 52mm, f/7.1 aperture. Note the background blur and how the horse's legs, which are moving more rapidly, are more strongly blurred...
7. Here's an experimental equestrian example done without fill flash, subject moving perpendicular to me, with even slower shutter speed and longer focal length: 1/25, 300mm at f/5.6...
8. Yet another shot with the same lens, settings and without flash... but this time with the subject coming more directly toward me, so is a little better defined...
9. For comparison, here's the same subject, lens etc. as above... except this time I froze all the movement with a 1/500 shutter speed (pls ignore the blown-out background. This is a lower resolution proof quality image. I fix backgrounds in my more finished images)...
10. Finally, here's a motion blur shot done much closer and with a much shorter focal length, much smaller subject running toward me... but still strongly motion-blurred by an extra slow shutter speed. 1/8, 12mm focal length, f/5.6...
Regarding the images where you want to make a sharp background (and foreground?), but allow the motorcycle to blur, will need to be done the same way... with a slow shutter speed. Except this time you should NOT pan the camera and follow the subject. Instead, keep it still and snap the shot as the bike passes through the image area. Depending upon how fast the motorcycle is moving, it may be really difficult to time the shutter release perfectly! I don't think I have any examples because it's not something I'd normally try to do.