Using ext tubes

It's a good question and one that I've never seen answered fully. It "feels" right to input the focal length as the lens length (e.g. 50mm) plus the length of the tube - so a 50mm lens plus a 25mm tube would be 75mm (or as close as you can get) in the SR settings. But, if you consider that a typical manual focus macro lens can extend in physical length by a significant amount then this calls this technique into question. A 100mm macro at infinity can be physically much shorter than at closest focus!

It has been discussed before that SR may not work so well for macro lenses as for others, so maybe the old fashioned techniques of high shutter speed (above the equivalent focal length of the lens), a tripod, or flash - plus turning off SR may work out better

I'll watch for suggestions/answers to this one

Is this the answer. link

The best way is to try it. Take a few shots with say 50mm, 75mm, 100mm etc. set in the camera at shutter speeds where blur is likely. See which setting provides the most keepers.

It's probably related more to magnification than actual length. Similar to Electronic First Shutter Curtain or EFSC which is worse at high magnifications.

http://www.robertotoole.com/blog/2014/01/28/electronic-first-shutter-curtain

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If you're using flash Derek, which I'm presuming you would be, would the flash duration not be short enough to negate any camera shake, within reason?
I've found that any blur caused by shake is more likely to be "fore & aft", rendering the image out of focus, rather than "shaken".

Roger

SR won't make any difference at 1/200th and 1/320th sec. It's around 1/25th sec. that it works best.

If you can get 1/200th only tests will tell if it's providing any benefit.

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On second thoughts using the 1/f rule anything up to 200mm would be sharp at 1/200th so no need to test. Improvement would be minimal and you shouldn't get any shake.


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should that be 1/(fx1.5) if it's a Pentax aps-c camera

If you accept that calculation to determine a lenses focal length, then I don't think adding extension tubes makes any difference to the focal length you should dial in.

e.g.
1/100 + 1/100 = 2/100 = 1/50
1/150 + 1/50 = 2/100 = 1/50
i.e. if you add to the distance between the lens and the sensor you reduce the distance between the lens and the object by the same amount.

Derek is using a K-1, but to be exact with APS-C the 1.5 factor should be included, but being a rule of thumb and people's own vibrations being different 1/f should be OK. Magnification of the final image also matters.

In all the testing I've seen they alter the FL of the lens so that they can compare different formats so 200mm APS-C would be recorded as a 133mm/130mm
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Magnification is a major factor with shake. using Love View, just watch the vibration with ultra close up and long telephoto images. It needs a good 10 seconds to settle down.