[chuck-e-cheese]

Hi all,

Here with another noob question. I just noticed that on my Tamron 70-300mm Di lens, I can't get the image stabilisation/shake reduction function to come up. Is this a capability that is not available on this lens? When I stick in my 18-55mm Pentax WR lens the shake reduction function does become available, hence I am a tad bit puzzled.

Thanks again for clearing this up for me guys!

[Adam]

SR works with all lenses. You may have to manually enter the focal length if it's not an AF lens, though.

[chuck-e-cheese]

SR works with all lenses. You may have to manually enter the focal length if it's not an AF lens, though.

Thanks Adam! I feel like such a doofus now! I took a look at the lens again and read briefly on entering the focal length on one of the forums. To my pea sized brain's astonishment, I had the lens set on A, once I moved the dial off this, SR was available.

I would be eternally lost without this forum!

[Laurentiu Cristofor]

You shouldn't have to do anything fancy to get SR to work with this lens. The 70-300 Di LD macro should work exactly as the 18-55 kit lens. Maybe there is a problem with the lens contacts and the camera body is not able to read the focal length to which the lens is set? You could try to clean the contacts with a Q-tip and a bit of alcohol.

[Marc Sabatella]

What makes you say SR is not available? With the aperture ring in the A position, you can't access the SR menu, but nor should you need to - that's only for lenses that *lack* the A position. Regular automatic lenses just work with SR, no menu required. What you are seeing that leads you to believe SR is not working when you leave the lens on "A"?

[Verglace]

I had the same lens for a while and it definitely worked at the 'A' setting. I'm guessing its one of the contacts... you should try cleaning them as suggested above.

[stanislav]

Shake reduction works with all lenses.

With auto-focus lenses (F, FA, FAJ, DFA and D lenses or compatible third parts) it works automatically since there is a "data" pin on the lens telling the focal length and to some extent even a focus point (not sure if focus point works om F lenses thou). The camera than compensates for shakes by actuallly mooving the sensor around so that the result should be as sharp as possible.

With manual focus lenses (K, M, A, and even M42 with adapters or compatible third parts) if the shake reduction is available you get an option to enter the focal length of the lens when as soon as you turn the camera on. Since there is no "data" pin the camera can read neither the focal length nor the focus point, so it relies completely on the value you entered when you powered up the camera. Note also that that is the value later shown in EXIF. The small problem here pose the old manual focus zooms, since you can not set the shake reduction to a "zoom" range but rather to a single focal length. You can still zoom but the bigger the difference between the actual focal length and the entered one the worse the shake reduction is going to work. You can experiment there a bit, but my suggestion is to either set SR to a focal range that you are most likely to shoot and/or where you want best qualities for your photos. The other approach is to get the SR to a lower part of zoom range since the wider the lens the les SR has to work.

Note also that data pin is of autofocus lenses works even if you set aperture on the aperture ring (set it to something other than A on F and FA lenses). So you still get the correct focal length in exif, but you won't get correct aperture value.

[m42man]

...You can experiment there a bit, but my suggestion is to either set SR to a focal range that you are most likely to shoot and/or where you want best qualities for your photos. The other approach is to get the SR to a lower part of zoom range since the wider the lens the les SR has to work...

Or better, use the compromise value calculated as follows: 2*Max*Min/(Max+Min)

This will give you the same amount of (reduced) SR whether you're fully zoomed-in or zoomed-out, so you'll always be a lot better off than having SR turned off.

But I don't think the OP's lens should have a problem here - the SR mechanism ought to be getting the correct FL info direct from the lens.

[stanislav]

Or better, use the compromise value calculated as follows: 2*Max*Min/(Max+Min)

This will give you the same amount of (reduced) SR whether you're fully zoomed-in or zoomed-out, so you'll always be a lot better off than having SR turned off.

What is your formula based on, is it some scientific calculation or based on best practices?

I would say that more "intuitive" approach would be to calculate the value as sqrt(Min*Max). However the results do not differ much than yours in most practical cases.

[m42man]

What is your formula based on, is it some scientific calculation or based on best practices?

I figured out the formula a while ago, and the basis is illustrated here:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/132496-shake-reduc...ml#post1380845

In terms of derivation, it's fairly easy to come up with two simultaneous equations defining the amount of sensor movement error at max and min zoom settings, and you combine these to end up with a value which equalises the SR at min and max zoom. If I remember correctly, as follows:

1. Fully zoomed in: SR effectiveness = x/H
2. Fully zoomed out: SR effectiveness = (2*L - x)/L

(where x is the value you're looking for, H is max FL, L is min FL)

Combining (1) and (2), for equal SR effectiveness whether zoomed-in or out: x = 2*H*L/(H+L)