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08-17-2007, 08:40 AM   #1
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old lens on new K10D

Hi there.

I already know what length to set when I attach my 50mm to K10D.
What about zoom lens like 28~80?
What focal length should I set?

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08-17-2007, 08:48 AM   #2
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wait I'm actually confused about the whole SR length selection thing. So of you mount a 50mm lens...do you enter 50mm into the SR menu or 75mm?
08-17-2007, 09:01 AM   #3
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The zoom thing has always been a mystery to me. Pete, for prime lenses, set the focal length of the lens, not the 35mm equivalent focal length. 50mm lens....set 50mm. 200mm lens....set 200mm.
08-17-2007, 09:21 AM   #4
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QuoteOriginally posted by jpmb76 Quote
Hi there.

I already know what length to set when I attach my 50mm to K10D.
What about zoom lens like 28~80?
What focal length should I set?
I would think you should set it to the focal length you anticipate using the most within your zoom range.

08-17-2007, 09:21 AM   #5
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Ok thanks cuz I was confused as SR seemed to blurr my photos and I getting scared that the camera was blurring my shots and not me.

Zoom, I heard somewhere that if you have the newer lenses, they communicate the focal length automatically to the camera body and in doing so, the SR system. Entering the focal length to my knowledge was always just for manual lenses.
08-17-2007, 09:28 AM   #6
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QuoteOriginally posted by jpmb76 Quote
Hi there.

I already know what length to set when I attach my 50mm to K10D.
What about zoom lens like 28~80?
What focal length should I set?

Flickr: Photos from jpmb76
Flickr: Just PENTAX!
You have two choices. Either set the camera for a focal length which will be in the middle of the zoom range you plan to use or take the time to set it for each individual shot. Depends on whether you have time or not. All this setting affects is the SR so the rest of the camera will function normally. The SR actually works too, it's just optimized if it knows the correct focal length...
08-17-2007, 09:41 AM   #7
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I too have read that you should set the focal length of the lens you are using so that the SR feature knows how to compensate, though, I've also read that the only reason you need to set the focal length is for proper EXIF data. Quite contradicting!

I'll make this comment. When I slapped on a manual focus 28mm f2.8 lens and did not set the focal length, the EXIF data showed that I used a 100mm for those shots (I assume 100mm was the last used prior to the 28mm).. All of the shots were taken with SR ON and all of the photos were exceptional! So, what exactly and how does the SR compensate? I'm not sure because it seems telling it bogus information results in perfectly fine photos.

I wish someone could detail what the how the SR function changes based on focal length.
08-17-2007, 11:38 AM   #8
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SR

If the lens you are using can comunicate with the body you do not need to set any focal length, it will be done automatically. This applies to primes and zooms. You will know if there is "comunication" when the SR menu is greyed out, if you try to set it manually.

If you use a lens that cannot comunicate you must set it manually. With a prime it is easy. if it is a zoom you must set the FL you are using for each shot. A bit tedious I know, so I would set the mid FL if it is a short range zoom. On a longer zoom you will have issues if you are shooting at 300mm and the SR is set at 70mm. Answer.....dont use the SR or get a modern zoom.

08-17-2007, 01:02 PM   #9
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QuoteOriginally posted by Tom M Quote
I too have read that you should set the focal length of the lens you are using so that the SR feature knows how to compensate, though, I've also read that the only reason you need to set the focal length is for proper EXIF data. Quite contradicting!

I'll make this comment. When I slapped on a manual focus 28mm f2.8 lens and did not set the focal length, the EXIF data showed that I used a 100mm for those shots (I assume 100mm was the last used prior to the 28mm).. All of the shots were taken with SR ON and all of the photos were exceptional! So, what exactly and how does the SR compensate? I'm not sure because it seems telling it bogus information results in perfectly fine photos.

I wish someone could detail what the how the SR function changes based on focal length.
Basically, the camera has a bunch of sensors in it that can tell whether the camera is rotating or not. Based on whether the camera is rotating upwards or downwards, the camera shifts the sensor to compensate.

The thing is that the degree to which the image shifts for a given change of the camera's angle depends on the focal length of the lens. For example, if you have a 20mm wide-angle lens and tilt the camera downwards one degree, you will barely notice the difference. Now if you have a 500mm lens and tilt the camera downwards one degree, your image shifts a great deal.

This is why the sensor needs to know the focal length of the lens for SR to work well. If it thinks the lens is shorter than it really is, it will undercorrect. If it thinks the lens is longer than it really is, it will overcorrect.

If you're getting "perfectly fine" images when the focal length is set improperly with SR, it means that you probably would have obtained the same quality images with SR turned off, i.e. you're not relying heavily on SR to improve the image.
08-17-2007, 04:41 PM   #10
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QuoteOriginally posted by Tom M Quote

I'll make this comment. When I slapped on a manual focus 28mm f2.8 lens and did not set the focal length, the EXIF data showed that I used a 100mm for those shots (I assume 100mm was the last used prior to the 28mm).. All of the shots were taken with SR ON and all of the photos were exceptional! So, what exactly and how does the SR compensate? I'm not sure because it seems telling it bogus information results in perfectly fine photos.
If the change had been in the other direction (SR set at 28, changed to 100mm lens without updating SR), you would have seen the difference. Same principle as why you can handhold shots at slower shutter speeds with shorter focal length lenses....the same size movement of the camera body just proportionately has less effect on the movement of the image on the film/sensor.
08-18-2007, 01:31 AM   #11
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QuoteOriginally posted by pschlute Quote
If the lens you are using can comunicate with the body you do not need to set any focal length, it will be done automatically. This applies to primes and zooms. You will know if there is "comunication" when the SR menu is greyed out, if you try to set it manually.

If you use a lens that cannot comunicate you must set it manually. With a prime it is easy. if it is a zoom you must set the FL you are using for each shot. A bit tedious I know, so I would set the mid FL if it is a short range zoom. On a longer zoom you will have issues if you are shooting at 300mm and the SR is set at 70mm. Answer.....dont use the SR or get a modern zoom.
Why should I buy modern zoom if I have few old ones in perfect working order?
I dont have SR on my SuperProgram and pictures are good, so it's not like I need this function, it's just good to know that i have an option to use it. Anyway I shoot with tripod when using zoom lenses.
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