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09-13-2018, 05:33 AM - 1 Like   #1
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AF Spot mode: hidden fact revealed - AF point is 30% smaller than in "select"

I have been using Pentax cameras for a while, but today I stumbled upon a piece of information which actually is news to me:

QuoteOriginally posted by Pentax:
Highlight: The advantage of Spot setting in AF mode

The Spot setting is an autofocus mode that detects the in-focus point using a single AF sensor positioned at the center of the image field.
For PENTAX digital SLR cameras marketed after the PENTAX K-3, the Spot setting detects an area approximately 30 percent narrower than that of the Select setting, which uses a set of middle AF sensors in autofocus operation.
Source: How to optimize focusing accuracy with large-aperture lenses / Beautiful Photo-life | RICOH IMAGING

I do consider this quite valuable information which I think was completely undocumented so far.

09-13-2018, 05:41 AM   #2
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SPOT or Select on central point are equal, at least on k-1, I checked. it's a bad translation or a wrong sense of the phrase.

There are some evidence that the statement on RICOH site are correct even if doing some tests the two modes look the same.

Last edited by Andrea K; 09-22-2018 at 10:51 AM.
09-13-2018, 05:46 AM - 3 Likes   #3
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You guys read manuals? Impressive...
09-13-2018, 06:06 AM   #4
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QuoteOriginally posted by beholder3 Quote
For PENTAX digital SLR cameras marketed after the PENTAX K-3
Seriously ? I thought this was also a feature on the K3.
What exactly does this difference in AF area would imply?

09-13-2018, 06:37 AM   #5
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QuoteOriginally posted by Andrea K Quote
SPOT or Select on central point are equal, at least on k-1, I checked. it's a bad translation or a wrong sense of the phrase.

Read more at: Make the Most of Your Pentax Camera: a Series of Articles Provided by Ricoh - Page 2 - PentaxForums.com
I would agree, that on the K-1 the area doesnt seem to be smaller (I just checked the central point though and dont know if the others in select might be larger).
09-13-2018, 08:12 AM   #6
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QuoteOriginally posted by beholder3 Quote
I do consider this quite valuable information which I think was completely undocumented so far.
QuoteOriginally posted by beholder3 Quote
I would agree, that on the K-1 the area doesnt seem to be smaller (I just checked the central point though and dont know if the others in select might be larger).
Fake news? I wonder how the Japanese version of the article reads. I had heard that the center spot was more selective, but not that it depends on how it is selected.


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09-13-2018, 08:20 AM   #7
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QuoteOriginally posted by stevebrot Quote
I wonder how the Japanese version of the article reads.
Google translate of the Japanese version (LINK) reads like this:

QuoteQuote:
Tips. Features of the AF point "Spot" "Spot" is a mode to focus on only the 1 point focus point.
For digital SLR cameras after K - 3, we are focusing by detecting a narrow range of about 70%, compared with the case of selecting the central focus detection point in the "select" mode.
It appears that they really mean a diameter 70% of what it would be if using "select". Any native Japanese speakers here?


Steve


Last edited by stevebrot; 09-13-2018 at 08:20 AM. Reason: Forgot to include URL for LINK
09-13-2018, 08:39 AM   #8
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70? 30?

perhaps the sense is that after the k-3 the central point is smaller than the k-3 central point in select?
09-13-2018, 09:23 AM   #9
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QuoteOriginally posted by Andrea K Quote
70? 30?

perhaps the sense is that after the k-3 the central point is smaller than the k-3 central point in select?
70% of vs. 30% less.

I would think that difference would be quite obvious with a simple test.*


Steve

* Still find it hard to believe that the center point sensor supports two FOV on top of the physical complexity of supporting cross-point and f/2.8 sensitivity.
09-13-2018, 09:40 AM   #10
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Hmm, I interpret the original posted statement very literal... that the single middle sensor is used in Spot setting and this equates to a measurement area approximately 30% of that resulting from a set (plural) of sensors about the middle used in Select setting. Unspecified in this particular paragraph is which set of sensors are involved in the Select setting. The OE information being stated for the sake of relative comparison in the areas being measured.
09-13-2018, 09:49 AM   #11
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QuoteOriginally posted by normhead Quote
You guys read manuals? Impressive...
I read the one that came with my K-3 and then promptly forgot most but hey at least now I can say I had forgotten about most of the features.
09-13-2018, 09:58 AM   #12
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QuoteOriginally posted by stevebrot Quote
* Still find it hard to believe that the center point sensor supports two FOV on top of the physical complexity of supporting cross-point and f/2.8 sensitivity.
As physically there are no separate horizontal or vertical focus "points" at all (both f5.6 and F2.8) but only one long line of pixels from which a deliberate decision in software takes a certain part (two parts actually, one on the left side and one on the right side), that is very easy. Firmwarewise they could easily offer 5 or 10 or 20 different AF point sizes.
09-13-2018, 10:01 AM   #13
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QuoteOriginally posted by One3rdEV Quote
Hmm, I interpret the original posted statement very literal... that the single middle sensor is used in Spot setting and this equates to a measurement area approximately 30% of that resulting from a set (plural) of sensors about the middle used in Select setting. Unspecified in this particular paragraph is which set of sensors are involved in the Select setting. The OE information being stated for the sake of relative comparison in the areas being measured.
Yes, the ambiguity of the English version may support your reading. What is less flexible is the Google translation of the Japanese site. The Japanese text, being assumed to be the basis for the English version, would indicate the authors intent. With any luck there will be clarification from Ricoh/Pentax at some point. At the very least, this tidbit will likely be part of the Pentax mythos for some time.


Steve
09-13-2018, 10:09 AM   #14
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QuoteOriginally posted by beholder3 Quote
As physically there are no separate horizontal or vertical focus "points" at all (both f5.6 and F2.8) but only one long line of pixels from which a deliberate decision in software takes a certain part (two parts actually, one on the left side and one on the right side), that is very easy. Firmwarewise they could easily offer 5 or 10 or 20 different AF point sizes.
One array in two sections can service both f/2.8 and f/5.6, but with separate microlens/prism. It takes two arrays of this type to do crosspoint.


Steve
09-13-2018, 10:23 AM   #15
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QuoteOriginally posted by stevebrot Quote
70% of vs. 30% less.

I would think that difference would be quite obvious with a simple test.*


Steve

* Still find it hard to believe that the center point sensor supports two FOV on top of the physical complexity of supporting cross-point and f/2.8 sensitivity.
I done the test.
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