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09-10-2010, 04:05 PM   #196
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SR and IS

QuoteOriginally posted by AngryCorgi Quote
VR = vibration reduction...SR = shake reduction...tomāto...tomăto...VR in-lens is tuned to a given focal length...SR in-camera is moving the sensor to match the vibration as is limited to the range-of-motion of the sensor within the camera...at any rate, it works best at normal FLs. The longer the FL, the less "shake reduction"...a canon or nikon 300mm lens with current-gen IS/VR will outperform "SR" with a 300mm lens easily.
Some lenses claim up to 4 stops, and Pentax SR is effective at maybe 3 stops. Unless you have Parkinson's disease anything past 2 or 3 is just ridiculous. Subjects move! If your shooting a landscape use a freaking tripod. Otherwise have a steady hand. I've shot with a Bigma @ 500mm on a Canon 20D (no IS) indoors at a conference (not very good light) iso 3200, the metadata on my jpg is totally off, so I have to find the RAW file to be sure on f stop and shutter speed, but I believe f7.1 at 1/40 or 1/50 hand held at an equivalent of 800mm.



09-10-2010, 04:06 PM   #197
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QuoteOriginally posted by Shashinki Quote
That was true 2 camera generations ago. The thing about SR however, it improves on every camera. So the lenses we buy today will have the top "VR XIV" or whatever they will call it in 10 years time and all we have to do is buy the camera itself.
That is simply not true at long FLs. Granted, given enough space to move the sensor thru a larger range of motion, you COULD improve the system, but there is nowhere near enough space in the current pentax bodies to accommodate the shift required to be as effective as a 300mm prime lens with VR/IS inside. The ideal scenario would be to have SR in the body for normal FL primes/zooms and VR/IS in the lenses for longer FL primes/zooms, since so few normal/portrait lenses currently have VR/IS and those that do are macros, not fast portrait lenses.
09-10-2010, 04:07 PM   #198
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QuoteOriginally posted by LFLee Quote
I only wish K-5 have interchangable battery with dedicated Litium-ion battery or AA battery, just like the K-r.
The wish is comprehensible. But not realistic.

The interchangeable battery option is on the edge of feasibility for the K-r and requires a careful limitation of power sinks. It makes more power-hungry features as are desirable for a pro caliber body very difficult to implement.

Because 4 AA are 4.8V only (Eneloops) while the LiOn is 7V.

Therefore, the K-7 offers the 6 AA option in the grip (7.2V) which is a good solution. AFAIK, the K-5 will have the same grip and option.
09-10-2010, 04:08 PM   #199
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QuoteOriginally posted by eccentricphotography Quote
I've shot with a Bigma @ 500mm on a Canon 20D (no IS) indoors at a conference (not very good light) iso 3200, the metadata on my jpg is totally off, so I have to find the RAW file to be sure on f stop and shutter speed, but I believe f7.1 at 1/40 or 1/50 hand held at an equivalent of 800mm.
Well, given ideal holding techniques (and mono/tripod), IS/VR/SR is not really necessary, but they will always raise the keeper-rate.

09-10-2010, 04:12 PM   #200
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QuoteOriginally posted by AngryCorgi Quote
Well, given ideal holding techniques (and mono/tripod), IS/VR/SR is not really necessary, but they will always raise the keeper-rate.
True, but past a certain point (say a lens with 6 stops) That is absolutely a marketing ploy.
09-10-2010, 04:15 PM   #201
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QuoteOriginally posted by creampuff Quote
Seeing from your profile that you're a new member and a Nikon user, I'll hazard a guess that you've never actually used a Pentax. So please provide substantive evidence to back up what you claim.
While I have not owned pentax cams, I have tried them at stores. I've not tried a K-7 for SR evaluation, but I have tried shooting and chimping with a K20D/18-55 kit setup in the past. I did not see acceptable results beyond 2 stops at 55mm. Can I provide "substantive evidence", no not personally as I didn't take the shots with my own card. I can point you to independent evals at independent labs that reach roughly the same conclusion. I got slightly better results with my old E-P1, but still never saw the claimed "4 stops" they tagged on the camera.
09-10-2010, 04:18 PM   #202
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QuoteOriginally posted by eccentricphotography Quote
True, but past a certain point (say a lens with 6 stops) That is absolutely a marketing ploy.
I agree.
09-10-2010, 04:29 PM - 1 Like   #203
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QuoteOriginally posted by AngryCorgi Quote
While I have not owned pentax cams, I have tried them at stores. I've not tried a K-7 for SR evaluation, but I have tried shooting and chimping with a K20D/18-55 kit setup in the past. I did not see acceptable results beyond 2 stops at 55mm. Can I provide "substantive evidence", no not personally as I didn't take the shots with my own card. I can point you to independent evals at independent labs that reach roughly the same conclusion. I got slightly better results with my old E-P1, but still never saw the claimed "4 stops" they tagged on the camera.
I studied that to some extent (final report is pending). The overall gain in stops thru out the range of exposure times is 2 stops for the K-7 SR. However, it has a weak spot around 1/80s where the gain can be less and a sweet spot around 1/15s where the gain exceeds 3 stops.

VR lenses don't beat the Pentax SR around it's sweet spot or for exposure times 1/200s and less for long tele lenses. Tele VR lenses typically don't deliver more than 2 stops either.

The comment that sensor shift is inferior because not tuned to a particular FL is wrong. The rotation of a shaking camera are FL-independent. Therefore, the antishake motion is simply exactly proportional to FL.


Last edited by falconeye; 09-10-2010 at 04:40 PM.
09-10-2010, 04:32 PM   #204
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QuoteOriginally posted by AngryCorgi Quote
there is nowhere near enough space in the current pentax bodies to accommodate the shift required to be as effective as a 300mm prime lens with VR/IS inside
What?

If you're shaking enough with your 300mm lens to induce a 200-pixel blur in your image during the exposure -- and that's a LOT of shaking to expect full correction for -- then the SR mechanism needs to move the sensor about a millimeter to correct it. (This assumes a 14-or-so megapixel sensor.)

That's not much!
09-10-2010, 04:33 PM   #205
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Here is one theoretical possibility how they could reduce flash sync speed with new flashes. Due to shake reduction, fully opened shutter uncover area larger than the sensor by few percent in each direction. So, if the camera knows precise position of the sensor, it can fire the flash at the moment when shutter curtains are not fully open, but don't obscure the sensor. Such high precision operation may require changes in the flash protocol.
09-10-2010, 04:36 PM   #206
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So first the Pentax SR cant exceed what it has today and then anything over 6 stops SR is a marketing ploy.
09-10-2010, 04:59 PM   #207
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QuoteOriginally posted by Shashinki Quote
So first the Pentax SR cant exceed what it has today and then anything over 6 stops SR is a marketing ploy.
Why would that be? Assuming you're *trying* to keep the camera still, the magnitude of movements isn't hugely different at 1/15th second vs 15 seconds.
09-10-2010, 05:50 PM   #208
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QuoteOriginally posted by sveinmb:
Your theory is somewhat correct, but no flash in the world is anywhere near as slow as that. A flashgun (or studio flash) will empty its full charge in less than a millisecond.
Considering t.1 flash durations, most of the speedlights at full power are something like 1/250s... The most of hot shoe flash manufacturers specify full power t.5 durations as something between 1/1000-1/800s, but t.1 is about 3 times longer than that... It is even worse with cheap studio flashes - they have t.5 1/800-1/1000s at full power, but reducing the power makes the flash duration longer (contrary to IGBT controlled speedlights)...
09-10-2010, 05:58 PM   #209
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QuoteOriginally posted by sveinmb Quote
Your theory is somewhat correct, but no flash in the world is anywhere near as slow as that. A flashgun (or studio flash) will empty its full charge in less than a millisecond.
You're mistaken here. Metz is the only (Pentax-compatible) flashgun maker to list T.1 durations (and they even do it for various powers — see the chart on my pttl site), and the 58 and 48 AF-1 have T.1 durations of 1/125th of a second. Even slower than 1/180th, and that's not even the complete zero-to-zero pulse.

Pentax's flashes are probably faster, but I suspect not by much.
09-10-2010, 06:45 PM   #210
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I can confirm at my retail store in Canada that the K7 is listed as DISCONTINUED ! as of 3 days ago.

They must have cameras to fill the gap... so I think it's likely what we're seeing
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