Image Stabilizer
canon400d
Banned Posts: 2,826 Major grins
I would appreciate it so much if anyone can tell me the reason for turning off IS when using a tripod. Am I right in saying the same applies to a monopod.
I must admit I never remember to turn it off.
Bob
I must admit I never remember to turn it off.
Bob
0
Comments
I think it's because the IS is designed to seek vibrations in your camera and compensate for (reduce) them. When the camera is stock still on a tripod the IS cannot find any vibrations to work with and, in effect, 'creates' some in it's efforts to function.
Anthony.
http://www.dlcphotography.net/TripodAndIS.htm
http://www.danalphotos.com
http://www.pluralsight.com
http://twitter.com/d114
Try shooting a frame with and without IS from a tripod, and see what you get. Post the frame s here on this thread. This is one area where your choice of shutter speed may make a lot of difference. I think the difference will be greater if shooting longer exposures than 1/30th or 1/60. Higher shutter speed frames will probably not be much different.
As the Chuck Westfall link shows, this was more of a problem with the earlier versions of IS.
Moderator of the Technique Forum and Finishing School on Dgrin
Thanks Anthony and Dan for replying. Thanks Pathfinder I will do that and see if there is any difference. In the past I have remembered to turn it off but I have never found any noticeable difference.
Thanks
Bob
Thanks once again.
Bob
the movement of the magnets causes vibration , always ( you can hear it )
even if you dont see different , switching it off saves battery-power
/ɯoɔ˙ƃnɯƃnɯs˙ʇlɟsɐq//:dʇʇɥ
When all else fails, run your own experiment and find out what happens, pixels are free.
Moderator of the Technique Forum and Finishing School on Dgrin
Thanks
Bob
shooting on a tripod, but very little about turning it off when
shooting at very fast shutter speeds with action photography.
I turn mine off when shooting at faster shutter speeds on the
premise that the camera will find focus faster. I don't know if
this is true, but it doesn't seem to negatively affect the outcome.
Comments on this welcome.
http://tonycooper.smugmug.com/
In my limited experience shooting wildlife, I find it is rather hard to monitor shutter speed from frame to frame, especially at the end of daylight when the light is dropping rapidly, as it does near the equator, and one's shutter speed can quickly fall from 1/500th down to 1/50th or even 1/15th as critters move out of the fading sunlight back into the shaded areas of the bush.
I took a workshop with John and Barbara Gerlach and they introduced me to Tv with Auto ISO, which I know is absolute heresy to some serious photographers, but I did try it in Kenya late in the day, when the sun is falling rapidly, and found I was getting nice images with a shutter speed still at 1/320th, that I was quite pleased with. AF was set to AI Servo of course, with IS on.
I was also quite surprised, however, when I found my ISO was set to ISO 12,800 by the Auto ISO setting at f5.6 the maximum aperture of my 70-300 L lens. I did not realize how dim the light had become bakc in the bushes. -- ISO 12,800 - the image must be horrible - right??
Here is that image in color and in my conversion to B&W. ( Recent lo noise DSLRs, and modern Raw engine like LR4, are necessary for this trick I do think. )
[imgl]http://pathfinder.smugmug.com/Travel/Kenya-2013/i-5HPCpGX/0/M/leopard in the woods_V6P9560-M.jpg[/imgl] [imgr]http://pathfinder.smugmug.com/Travel/Kenya-2013/i-DkbvBhT/0/M/leopard_in_weeds_monochrome-2-M.jpg[/imgr]
One can debate the merits of my image, but I do not think noise in it is a serious issue.
If you KNOW your shutter speed is not going to fall, and that it will remain faster than 1/1500th or more, then I agree I do not think IS makes a great deal of difference.
Moderator of the Technique Forum and Finishing School on Dgrin
http://tonycooper.smugmug.com/
It sounds as if you can be relatively certain that your lighting is not going to change radically during your shoot, in which case a fixed ISO makes good sense, and Tv or Manual mode means that you KNOW for certain what your minimum shutter speed is.
My situation was different in that I knew the lighting was going to change fairly radically, and could change 5 or more stops by merely changing the direction of my camera axis, so for me, in that situation, Tv with Auto ISO was a reasonable choice. At least with a 5DMk III or similar camera with good high ISO performance
Other folks may prefer Av with active watching their shutter speed, which was my preferred method for years, but I would have missed my shot of the leopard in the deep forest, because I had no idea it would need an ISO that high, or my shutter speed would have plummeted. I have never deliberately chosen an ISO higher than 1600 or 3200 in extreme situations, which still would have left me with a shutter speed 2 stops slower than 1/320th.
My point is that no one method is the sole method of choice, but that there are several ways to skin a cat.
I agree that IS/VR means very little at shutter speeds faster than 1/1000th or so. Folks forget that even with very high shutter speeds, with a focal plane shutter, it still takes about 1/250th of a second for the shutter to go from opening to final closing, as the slit travels across the sensor face.
Moderator of the Technique Forum and Finishing School on Dgrin
http://tonycooper.smugmug.com/
Like you, I kind of think it might be marginally faster without it, but not enough to alter my shooting routine, at least for me.
A quick google turned up a few links, that I am not sure I fully agree with, but what the hey
http://www.bythom.com/nikon-vr.htm A few years out of date, perhaps... It agrees with you that at shutter speeds faster than 1/500th IS should be turned off.
http://photography-on-the.net/forum/showthread.php?t=298360 = a web forum discussion of the issue, that feels there is no difference once IS has spun up, i.e. is active.
A quick perusal of the manual from Canon for my EOS 70-300 f4-5.6 IS L says nothing about turning the IS off at high shutter speeds at all. It even suggest leaving it on with a monopod sometimes.
Moderator of the Technique Forum and Finishing School on Dgrin
My current "belief", and the possible science behind the belief, follows:
2) The measured phase difference allows the "processing" section of the autofocus system to determine current focus position at the sample region; fore, aft or correct focus. Autofocus direction and degree (AF vector) information is generated and communicated to the autofocus "steering" circuits which guide the lens' autofocus motor and drive to the calculated E-RF parity. (Ideally, that is the prime focus for the subject.)
3) The strength of the AF signal (used for the AF sample data) is dependant upon, AF sensor sensitivity, available/ambient light (and/or additional light from a focus illumination lamp or AF assist light), AF module design (including AF lens size and design, any additional apertures internal to the AF module) and the AF sensor dynamic range (specifically the point at which sensor noise obfuscates sensor data and what the data slope and data vectors do just before that point.) The taking lens' maximum aperture factors in, as does the lens' contrast.
4) E-RF discrimination is only possible with subjects of sufficient contrast to provide valuable AF sample data "and" with subjects sufficiently illuminated to provide sufficient AF data strength.
5) Subject Blur (SB) (where "subject" is defined as the area under AF scrutiny and where "blur" is defined as motion rapid enough with respect to AF sample speed to cause an AF sample variation), caused by either subject motion or camera motion or both, has the effect of reducing AF subject contrast, thereby reducing AF speed and AF accuracy.
Accepting the above D&C allows explorations of various autofocus scenarios.
In particular, and to answer Tony Cooper's question, ...
"If" you use optical image stabilization (OIS) to provide a more crisp subject image to the autofocus (AF) system, "then" the AF system views the AF data sample with having higher contrast, which should improve AF acquisition speed and AF accuracy. Indeed, this seems to be the case by my own unscientific empirical testing and use.
To know when OIS is beneficial to the AF system requires some knowledge of the OIS system in use.
All OIS (aka "lens based" stabilization) systems have a "settle and lock" period, during which AF may be impaired. All OIS systems that I'm aware of also have a specific, but unique to each system, duration, which can be re-activated and extended.
"If" the OIS is previously "locked", "then" it is presenting a more stable image to the AF system, so if you activate AF while OIS is locked it should acquire faster due to the reduced subject blur as defined above in section 5 of the D&C.
Other factors will have some effect on the outcome such as:
Specific AF settings in the camera as in:
AF settings related to release vs focus priority.
Specific OIS systems. Different OIS systems have different qualities, so each manufacturer, model and version needs to be evaluated and understood before you can expect predictable results.
Specific AF systems. Similar to the above, AF systems have differences related to different modes of operation as well as different sensitivities and different durations and responsiveness.
Subject contrast. Subject matter under AF scrutiny may still not lock focus, or may lock focus more slowly, regardless of OIS, if it lacks sufficient contrast. Locked OIS should improve the AF results but cannot guarantee AF results.
Ambient light. Autofocus requires sufficient light in order to operate. In extremely low light, OIS may not make any difference at all. However, it probably will not hurt AF either, once OIS is locked.
Subject motion. OIS does not help with subject motion, unless the OIS has a panning/tracking mode (even an automatic tracking mode) "and" the camera/lens is accurately tracking the subject. In that condition, OIS may help control subject blur when locked, allowing faster autofocus acquisition.
Camera motion. Camera motion, especially camera shake due to operator shake, is what OIS is designed to counter and control. Other types of camera motion, like motion due to vibrations caused by other sources (vehicular, horseback, heavy machinery, wind, etc.) may not be as well controlled by OIS. If OIS is not working properly from one of these causes, it will certainly not help with AF acquisition. Similarly, not all OIS systems have equally competent panning/tracking capability.
One-shot vs predictive continuous autofocus. I don't know why, but this issue continues to trip up even well known professionals. One-shot AF typically takes a single sample of the AF in order to operate the AF system. Predictive continuous autofocus, aka AI-Servo/AF-S mode, "requires" a short period to sample subject motion, before it can accurately predict and set AF. The sample period for AI-Servo/AF-S mode needs to be added to the OIS settle time to work in harmony.
There are a few lesser significant items which I'll ignore for now.
Finally, my short(er) observations and summary with recommendations.
For sports/action which has irregular or spontaneous activity and doesn't allow you to plan and anticipate, I recommend leaving OIS off and using one-shot AF too. The sample period for AI-Servo/AF-S mode and the OIS settle time will probably lead to more frustration than desirable results. A body and lens designed for sports/action is very much indicated.
For sports/action which has predictable movement of the subject(s), and which allows you to plan and compose the shot, may allow you time for the sample period for AI-Servo/AF-S mode and the OIS settle time, so you may wish to try that combination and let the results dictate what you use. (Test, evaluate, learn, apply.) Certain horse events might fall in this category, for instance.
For sports/action which has "mostly" predictable movement of the primary subject(s), but where the primary subjects may change, I think that AI-Servo/AF-S mode is indicated, but OIS is probably not indicated. Basketball shot from court-side, for instance. Some automobile races as well. A professional sports/action body and lens is recommended to keep up with the action, as well as custom AF settings.
For some automotive races, depending on your position relative to the race, OIS and AI-Servo/AF-S "could" be valuable. Shooting a race from the spectator stands, for instance. (Hardly an ideal position for much of the drama, however.)
For mostly static scenes and subjects in subdued light, where you are mostly trying to combat user camera shake, I think that the combination of OIS and one-shot makes sense. It may not help as much as some would want, but I don't see any harm either.
I suppose that the point is if you can "see" a shake benefit through the viewfinder and still have time for the shot, the AF system will "sense" the shake reduction as higher contrast subject matter (item 5 above), and the result should be an improved AF experience and result. My tests and personal experience seem to bear this out.
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Thanks again
Bob