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05-20-2009, 01:24 PM   #1
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K7 - Secondary Focusing Sensor

Could somebody enlighten me about the Secondary Focusing Sensor?

YouTube - PENTAX K-7 Introduction

at 6'15"

05-20-2009, 01:28 PM   #2
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I read somewhere else that there is a color sensor that helps the camera decide how to bias the AF system to correct for AF errors under different lighting conditions (daylight vs incandescent, etc). This may be this "secondary" focusing sensor that they are referring to. I'm not sure but it's my best guess.

-Jim
05-20-2009, 01:35 PM   #3
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Another possibilty

QuoteOriginally posted by soalle Quote
Could somebody enlighten me about the Secondary Focusing Sensor?

YouTube - PENTAX K-7 Introduction

at 6'15"
AF sensors have to be set for a certain lens baseline. Fast lenses usually need a much wider gap between the 2. Canon has one aF sensor type for lenses f2.8 (approx) or faster. Another one for faster lenses.....
05-20-2009, 01:39 PM   #4
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QuoteOriginally posted by jeffkrol Quote
AF sensors have to be set for a certain lens baseline. Fast lenses usually need a much wider gap between the 2. Canon has one aF sensor type for lenses f2.8 (approx) or faster. Another one for faster lenses.....
so are we sure that is for fast lenses? Till which aperture?

05-20-2009, 02:00 PM   #5
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the ability of the camera to detect the light colour used to focus intriges me.

Could this mean the end of front focus under incandescent light?
05-20-2009, 02:05 PM   #6
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QuoteOriginally posted by soalle Quote
so are we sure that is for fast lenses?
The answer seems to be no.

"light-color sensor has been added that improves focus accuracy under light sources with widely varying hues."
Pentax K-7 Digital Camera - Hands-On Preview - The Imaging Resource!
05-20-2009, 02:09 PM   #7
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QuoteOriginally posted by jeffkrol Quote
AF sensors have to be set for a certain lens baseline. Fast lenses usually need a much wider gap between the 2. Canon has one aF sensor type for lenses f2.8 (approx) or faster. Another one for faster lenses.....
What I've seen so far says that the secondary sensor is to account for different light types--tungsten, flourescent, etc.
05-20-2009, 10:49 PM   #8
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By John C. from Pentax:

"That is the + in the SAFOX VIII+ name. The secondary sensor determines the light source and makes micro adjustments to the focus based on the different wave lenghts of light for that source."

05-21-2009, 12:25 AM   #9
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Finally!

QuoteOriginally posted by soalle Quote
Could somebody enlighten me about the Secondary Focusing Sensor?

YouTube - PENTAX K-7 Introduction

at 6'15"
They finally listened!

I recall back to 2005, I was one of the first Pentax users who complained about the Front Focusing of the SAFOX VIII AF system of the Pentax DSLRs under Tungsten lights and finally did some quick experiments to verify the thing.

Of course, I was bashed to death, most of the Pentax fanboys didn't admit there was a problem and it was just an "user error" afterall!

Now, even Pentax have admitted the issue and have made design improvement! They read my Blog and webpages? :-))
05-21-2009, 03:37 AM   #10
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QuoteOriginally posted by KungPOW Quote
Could this mean the end of front focus under incandescent light?
Yes.

The speculation by imaging resource as to why it is necessary to make the correction (prisms in AF system are sensitive to the wave length of incoming light and hence only work well for a limited bandwidth) has been my hypothesis all along (posted about this sometime ago).

I believe the new system is not so much a result of listening to bloggers , but more one of a commitment to offer a high-specd camera for more than an entry-level price. Its great to see Pentax doing this! The K-7 is an awesome package. If only they didn't put a rubber door on it. <- I'll add this complaint do every post I make from now on.
05-21-2009, 05:15 AM   #11
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QuoteOriginally posted by RiceHigh Quote
They finally listened!

I recall back to 2005, I was one of the first Pentax users who complained about the Front Focusing of the SAFOX VIII AF system of the Pentax DSLRs under Tungsten lights and finally did some quick experiments to verify the thing.

Of course, I was bashed to death, most of the Pentax fanboys didn't admit there was a problem and it was just an "user error" afterall!

Now, even Pentax have admitted the issue and have made design improvement! They read my Blog and webpages? :-))
To be honest (which you are rarely 100%) there were some that said user error, some (such as I ) thought it had to do w/ quantity of IR and IR sensitivity of the sensor. Some just thought it was "within tolerances". Some like me thought your setup for testing had some scientific deficiencies and some needed more tests from other sources. Nobody in their right mind should believe one squeaky wheel. You try to make things so black and white. At one point I pointed out to you that some Canon's had focusing problems under flourescent light so it was a known issue for all brands (Canon et. al.). You didn't want to hear it.
And besides, this issue should have been known (and I believe was) since film days. Nothing changed that much in the AF system since except accommodations to a "new film".
And since I will have to repeat this line for weeks to come....
Most likely you had very little influence on Pentax, blog or not. If it makes you feel good to BELIEVE you did so be it.


The phrase is........
"Get over yourself"......
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