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02-11-2011, 12:26 AM   #16
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QuoteOriginally posted by v5planet Quote
Well I meant more so: would leaving it on be to the detriment of the photo in such a circumstance? Doesn't sound like it, but I asked because it's not something I think I would trust myself to remember to do (turning off the SR) when a hand held closeup opportunity presented itself.
The SR switch on my K20D is easily flicked, so I don't have a problem there when actually shooting macro, as opposed to close-focus.

As to whether SR diminishes IQ in handheld macro -- I do not know. I have not tested that. I suspect that leaving SR on may give the shooter a false sense of security, leading to clumsiness. I also suspect that adding great extension, or using an internal-focus macro lens, may change the effective focal length enough to outwit the SR'bot.

My K20D's SR is 2-dimensional, handling X- and Y-axis rock'n'roll but not Z-axis. I recall reading of rumours of 3D SR that CAN handle Z-axis movement. I've also heard rumours of Santa Claus, so I'm not sure what to believe.

QuoteOriginally posted by m42man Quote
As you're probably aware, I did some calculations regarding the best compromise FL for a vintage zoom, but I hesitate to post the link for fear of boring everyone!
No, please bore us. Redundancy is the soul of communications.

02-11-2011, 01:32 AM   #17
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QuoteOriginally posted by RioRico Quote
...No, please bore us. Redundancy is the soul of communications.
Well, with an invitation like that, how could I refuse (you do have a talent for the pithy observation though)!

Rather than post a link or two, I'll try to illustrate what's going on SR-wise:

With SR off, camera shake will result in a certain amount of image blur, caused by movement of the image relative to the sensor.

The object of SR is to move the sensor by just the right amount, in order to exactly counter the movement of the image caused by the shake. With the correct FL information, the camera is able to do this (well, nearly).

So, assume a 100mm lens:

SR off, sensor moves 0% of ideal, you get 100% blur.

SR on:
Set FL value to 25mm. Sensor moves 25% of ideal, you get 75% blur.
Set FL value to 50mm. Sensor moves 50% of ideal, you get 50% blur.
Set FL value to 75mm. Sensor moves 75% of ideal, you get 25% blur.
Set FL value to 100mm. Sensor moves 100% of ideal, you get no blur.
Set FL value to 125mm. Sensor moves 125% of ideal, you get -25% blur.
Set FL value to 150mm. Sensor moves 150% of ideal, you get -50% blur.
Set FL value to 175mm. Sensor moves 175% of ideal, you get -75% blur.
Set FL value to 200mm. Sensor moves 200% of ideal, you get -100% blur.
Set FL value to 225mm. Sensor moves 225% of ideal, you get -125% blur.
etc. etc.

A negative sign is used to indicate that the blur is now acting in the opposite direction to the original (not that this matters).

So at 200mm, you get the same blur as with SR off (but in the opposite direction).

Using the above model, you can devise a formula which gives an optimum compromise value for a zoom lens. It turns out this formula is

Best compromise FL value = 2*H*L/(H+L)

Where H is the max FL of the zoom, L the min FL.

Using this for some popular vintage zooms:

28-70: theoretical setting: 40mm, actual setting: 40mm, max blur: 43%
28-80: theoretical setting: 41mm, actual setting: 40mm, max blur: 50%
28-90: theoretical setting: 43mm, actual setting: 40mm, max blur: 56%
28-105: theoretical setting: 44mm, actual setting: 45mm, max blur: 61%
35-70: theoretical setting: 47mm, actual setting: 45mm, max blur: 36%
35-105: theoretical setting: 52.5mm, actual setting: 50mm, max blur: 52%
35-135: theoretical setting: 56mm, actual setting: 55mm, max blur: 60%
70-150: theoretical setting: 95mm, actual setting: 100mm, max blur: 43%
70-150: theoretical setting: 95mm, actual setting: 85mm, max blur: 43%
75-150: theoretical setting: 100mm, actual setting: 100mm, max blur: 33%
70-210: theoretical setting: 105mm, actual setting: 100mm, max blur: 52%
80-200: theoretical setting: 114mm, actual setting: 100mm, max blur: 52%
80-200: theoretical setting: 114mm, actual setting: 120mm, max blur: 50%
80-210: theoretical setting: 116mm, actual setting: 120mm, max blur: 50%
60-300: theoretical setting: 100mm, actual setting: 100mm, max blur: 67%

If you were able to set the exact theoretical setting, you'd get maximum blur at each extreme of the zoom range. Choosing the nearest lower FL value will favour the wider end, and vice versa for the nearest higher value. Obviously, if you have the zoom set to exactly match the value you entered, you'll get full SR.

Anyway, you can see from the above that you can get quite reasonable SR for lenses with modest zoom ranges (and let's face it, you wouldn't want a vintage zoom with a big zoom range for reasons of IQ). 50% blur implies 1 stop of SR - not nearly as good as the 3-4 stops maybe for full SR, but still worthwhile.

Having said all that though, there aren't too many vintage zooms out there which are worth putting on your camera (in my view, anyway)...
02-11-2011, 06:41 AM   #18
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QuoteOriginally posted by m42man Quote
(you do have a talent for the pithy observation though)!
Oh yeah, I'm just full of pith. Hey, thanks for the formula! I've incorporated it into my lens database for the 5% of my ~180 lenses that are manual zooms. Guess I'll tape the numbers onto the lenses themselves too.

QuoteQuote:
Having said all that though, there aren't too many vintage zooms out there which are worth putting on your camera (in my view, anyway)...
Total agreement there. That's why my paradigm is: AF zooms, manual primes.

Last edited by RioRico; 02-11-2011 at 07:58 PM.
02-11-2011, 03:08 PM   #19
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SR is always on, including video mode.

02-12-2011, 01:56 AM   #20
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QuoteOriginally posted by RioRico Quote
Oh yeah, I'm just full of pith. Hey, thanks for the formula! I've incorporated it into my lens database for the 5% of my ~180 lenses that are manual zooms. Guess I'll tape the numbers onto the lenses themselves too.
Pleased to be of assistance!

I thought my collection of a couple of dozen lenses was bad enough - you don't think you have a touch of LBA there?

(Only joking, I think lenses are good!)
02-12-2011, 03:49 AM   #21
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QuoteOriginally posted by m42man Quote
I thought my collection of a couple of dozen lenses was bad enough - you don't think you have a touch of LBA there?
"My name is RioRico and I am an optics junkie." Oops, wrong forum.

LBA? Moi? No, just call it... curiosity. [/me sinks slowly into glass morass...]
02-20-2011, 12:25 PM   #22
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I use SR, except when i'm indoors shooting live theatre. The logic is this:

A. With the older dslrs like the K10, K20, not sure about the K7, there was a 1 or 2 second startup time for the SR. During that startup time, the effectiveness of the SR is incalculable. Rather than risk having the SR work against the image, i turn it off. (with the K5, i understand that there is an ability to turn it on and have it stay on for some length of time.

B. With live theatre, capturing the motion of the actors is more important than the shake of the camera. 1/30 is often not adequate. I use a mid tele zoome, 28 to 75mm. The shutter rule of thumb to keep 75 mm steady is 1/1.5*75 or 1/125sec roughly. Well guess what, 1/125 sec on up to 1/200sec can drastically improve the odds of getting sharp pictures of actors. With my K20, i drastically improved my keeper rate by using faster shutter speeds, even with more noise. When i move to the K5, I won't have to choose so much between faster shutters and noise - yeah.

When you are dealing with human action situations, the faster shutter speeds negate the value of SR.

i'm not saying there aren't times when SR isn't useful, I've just learned that it often isn't so useful for live theatre. IMO - incoming
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