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11-06-2011, 06:40 PM   #1
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K5: What's the latest findings in Mixed lighting Front Focusing issue?

IMPORTANT UPDATE:
- The FF issue *may not* be low light related in this particular case
- see updated post at post #44 on page 3.


Did we ever collect enough data on the forum to determine if this is a individual sample variation or a model wide problem.
Has it actually been addressed by firmware updates?
On a recent outing, I took some snap shots (snap shots indeed - crowded theatre, on stage performance, weary of shutter noise disturbing other viewers, these are quick shots taken) at the Qi Live show featuring Steven Fry @ QPAC Brisbane.
I used a K5 + FA77 combo. Matrix metering/ Center AF point. No flashing. All the auto focus shots display a huge amount of FF in the region of I suspect a meter or 2.


100% crop - My intended focus spot is of course, Mr. Fry. But note the actual in focus area is on the front row audiences. (the back of the head is clearer than the performer's faces!). My seat is about 15 meters back.

Here is one I manual focused on the action:


I didn't give it much thought when I fired off the first batch AF sots. Until at the interval I had a quick check and decided to manual focus for the rest of the event. In between I fired a few AF test shots and all the AF shots exhibited the huge FF.
My K5 is running firmware 1.03, the 1.10/1.11 updates appear to be adding features for the GPS unit and didn;t list any focus issues in the fix list. This FA77 has also been calibrated in normal lighting conditions - certainly an error of FF by meters is not a known issue under other conditions!
I am happy to MF for use Live view zoom to check focus spot. But like a head count of how many here still experience mixed lighting front focus.


Last edited by Katsura; 11-25-2011 at 12:00 AM.
11-06-2011, 06:43 PM   #2
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Here are a couple of samples from a trip in Japan this May. Of the Miyajima floating torii gates.
The gates are lit by mercury(?) flood lights at night.
Here is one took via Phase detect AF:


And here is one taken in live view via Contrast measure AF:


The live view AF is more accurate while the phase detect AF shows signs of FF. The lens used in a FA*28-70, again, calibrated to be accurate otherwise.
This pair of picture is from about a dozen I took and each pair shows accurate focusing in Live View mode and FF in Phase detect mode.
Do note that the live view pictures white balance AND metering is not accurate compared to the standard mode. The live view seem to expose much brighter and has a more yellow tint in white balance than the actual subject.
The standard mode exposes more accurately and the colour, at least according to my naked eyes, is a lot closer, to what the subject actually looks like.
I didn't change any settings between the live view and standard mode shots - what is to account for the large difference between the white balance (I think this has got something to do with the AF accuracy!) and exposure?
11-06-2011, 07:36 PM   #3
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I'm interested too, I haven't found a solution, I'm guessing a -20 adjustment would work for my camera. So a few thousand dollars worth of gear, professional gig and I'm manual focusing... old school I guess.
My current thinking is to get an ees screen for my viewfinder...
I have thought about a laser pointer, and testing if it works as AF assist light, but I can't have a visible dot in my shots.
11-06-2011, 09:33 PM   #4
Brooke Meyer
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I don't think it is an equipment problem.

I've taken thousands of performance photos with two uncalibrated K-5s using a Tamron (28-75), Pentax (50-135) and a Sigma (100-300) and the only difference between the two K20's I used to use in that the K-5 is really quiet and non patron annoying and the ISO performance is lots better. Oh,yeah , the frame rate and buffer

Through experience, I have learned to shoot manual exposure and RAW or don't expect much. Wouldn't matter if it was Canon or Nikon. Same with using the AF button on the back & center point and recompose if necessary. Wouldn't matter if it was Canon or Nikon. Acquire and track the subject. You cannot throw it up, mash the shutter half way and expect instant magic. Pre focus. Listened to a 40 year experienced, nationally known and heavily awarded Press photographer who is now winning lots of Wildlife contest for stunning birds and he said the same thing, Shoots Nikon D3.

I shot this last Friday night at a local Arts Ball. 50-135 pretty open at f4, 1/125 & ISO 12,800 plus a Pentax 540 straight up and the catch light panel reversed like a flag. Had mixed light all night long, Fluorescent, Tungsten, LED, Flash, you name it. Controlled everything in RAW based on experience and watching the histogram and image.

If you invest the time to learn, you will be rewarded.

Attached Images
 
11-06-2011, 09:55 PM   #5
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Brooke are you saying that you only manual focus?

I photograph fast moving subjects (acrobats, dancers etc), have taken thousands of images too. I can understand pre focusing on musicians, who stand still.
Did your AF focus correctly last Friday night?
11-06-2011, 09:58 PM   #6
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QuoteOriginally posted by Brooke Meyer Quote
I've taken thousands of performance photos with two uncalibrated K-5s using a Tamron (28-75), Pentax (50-135) and a Sigma (100-300) and the only difference between the two K20's I used to use in that the K-5 is really quiet and non patron annoying and the ISO performance is lots better. Oh,yeah , the frame rate and buffer

Through experience, I have learned to shoot manual exposure and RAW or don't expect much. Wouldn't matter if it was Canon or Nikon. Same with using the AF button on the back & center point and recompose if necessary. Wouldn't matter if it was Canon or Nikon. Acquire and track the subject. You cannot throw it up, mash the shutter half way and expect instant magic. Pre focus. Listened to a 40 year experienced, nationally known and heavily awarded Press photographer who is now winning lots of Wildlife contest for stunning birds and he said the same thing, Shoots Nikon D3.

I shot this last Friday night at a local Arts Ball. 50-135 pretty open at f4, 1/125 & ISO 12,800 plus a Pentax 540 straight up and the catch light panel reversed like a flag. Had mixed light all night long, Fluorescent, Tungsten, LED, Flash, you name it. Controlled everything in RAW based on experience and watching the histogram and image.

If you invest the time to learn, you will be rewarded.
Brilliant shot as demonstrated by your photo, but that is not the point nor the aim of discussion intended here.

If I'd known the set up the stage I would have used a longer lens to start with and certainly not the FA77 for this event (purple fringe monster). And yes I would happily manual focus and adjust exposure manually had I been the press photographer for the event, as I said. I feel bad even getting my camera OUT for the shots. They are indeed, snap shots intended for Facebook rather than to put up in a gallery.

However, as you can see, although my MF shots are adequate for Facebook, the AF shots missed it by meters.

Hence the aim of the thread is to gather the information, if others experience the FF issue when doing quick and dirty AF shots in setups like this.
11-06-2011, 10:03 PM   #7
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QuoteOriginally posted by Turtle Quote
I'm interested too, I haven't found a solution, I'm guessing a -20 adjustment would work for my camera. So a few thousand dollars worth of gear, professional gig and I'm manual focusing... old school I guess.
My current thinking is to get an ees screen for my viewfinder...
I have thought about a laser pointer, and testing if it works as AF assist light, but I can't have a visible dot in my shots.
It WOULD be interesting to find out if a laser pointer will help. obviously, not going to help on a stage show. But it might help to determine the cause of this problem.
11-07-2011, 03:14 AM   #8
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Katsura, the EXIF of your images has been stripped of the Manufacturer's Notes section. What does that section of the EXIF say about your focus point, AF adjustments, and exposure?

(A tool like PhotoMe is very useful here - I prefer the 0.79R17 version).

11-07-2011, 05:22 AM   #9
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Center point AF, I think -0.3 Exposure on the 1 events photos and -3 Ev on the 2 gate ones.

The stripping is done by the Album uploader here - the same photos posted at DPR retained the exif data.
11-07-2011, 05:33 AM   #10
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QuoteOriginally posted by Katsura Quote
The stripping is done by the Album uploader here - the same photos posted at DPR retained the exif data.
Incorrect. Your DPR images are also missing much of their EXIF, including the Manufacturer's Notes.

Using the wealth of information available in your FULL EXIF should be your first point of reference for debugging this kind of issue. I suggest downloading PhotoMe and opening up your straight-out-of-camera JPG's or RAW's. Then you'll see the full record.
11-07-2011, 05:52 AM   #11
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Night shots K-5

Here are a couple of pics taken at 05:15 in the morning ,Pentax K-5 and Sigma 300mm f2.8 EX DG




11-07-2011, 06:07 AM   #12
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QuoteOriginally posted by Ducatigaz Quote
Here are a couple of pics taken at 05:15 in the morning ,Pentax K-5 and Sigma 300mm f2.8 EX DG
Great sharp images. No FF visible

Gee, how old would that Dragon Lady be?
11-07-2011, 06:14 AM   #13
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QuoteOriginally posted by rawr Quote
Incorrect. Your DPR images are also missing much of their EXIF, including the Manufacturer's Notes.

Using the wealth of information available in your FULL EXIF should be your first point of reference for debugging this kind of issue. I suggest downloading PhotoMe and opening up your straight-out-of-camera JPG's or RAW's. Then you'll see the full record.
I have PhotoMe, but what particular information are you looking for?
11-07-2011, 06:15 AM   #14
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QuoteOriginally posted by Ducatigaz Quote
Here are a couple of pics taken at 05:15 in the morning ,Pentax K-5 and Sigma 300mm f2.8 EX DG r
AF I presume?
11-07-2011, 06:23 AM   #15
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This is for the blurred AF event photo


[PhotoME]
PhotoME version: 0.79R17 (Build 856)

[Overview]
File name: C:\Temp\2011_10 Qi Live Brisbane\IMGP4453.PEF
File type: Pentax Camera RAW
File size: 17,716.9*KB
Creation date: 31/10/2011 23:10
Last modification: 31/10/2011 23:10
Make: PENTAX (PENTAX)
Camera: PENTAX K-5
Lens: K or M Lens
Software: K-5 Ver 1.03
Dimension: 4992 x 3284*px*(16.4 MP, 3:2)
Focal length: 77*mm*(equiv. 115*mm)
Aperture: F2.5
Exposure time: 1/60"
ISO speed rating: 400/27
Program: Program AE
Metering Mode: Pattern
White Balance: Auto
Focus Mode: AF-S
Image Stabilizer: stabilized
Noise Reduction: Off
Flash: Flash did not fire, compulsory flash mode

[Manufacturer notes]
Pentax Version: 70.0.0
Pentax Model Group: Group 1 (DSLR series & Various Optio models)
Preview Image Size: 640 x 480
Preview Image Length: 37049*bytes
Preview Image Start: 0x00008A20
Pentax Model: 0x12e76
Date: 2011-10-31
Time: 23:10:10
Quality: RAW
Flash Mode: Off; Internal
Focus Mode: AF-S
AF Point Selected: Center
Exposure Time: 1/60"
F Number: F2.5
ISO: 640/29
Exposure Compensation: 0
Metering Mode: Multi-segment
Auto Bracketing: 0 EV, No Extended Bracket
White Balance: Auto
Focal Length: 77*mm
Saturation: Normal
Contrast: Med High
Sharpness: Med Hard
DSP Firmware Version: Ver 1.03.22.11
CPU Firmware Version: Ver 1.03.22.11
Effective LV: 6.4*LV
Picture Mode: MTF Program (Hyper-Program); 1/3*EV steps
Drive Mode: Continuous; No Timer; Shutter Button; Single Exposure
??? (0035): 12061, 7988
Color Space: sRGB
Image Area Offset: x = 22*px, y = 10*px
RAW Image Size: width = 4928*px, height = 3264*px
??? (003D): 8192
Preview Image Borders: top = 28, bottom = 28, left = 0, right = 0
Lens ID: 4*+*24*+*0*+*0
Pentax Lens Type: FA, FAJ, DFA or DA
Lens Name(s) of the ID: smc PENTAX-FA 77mm F1.8 Limited
Camera Temperature: 29*C
AE Lock: Off
Noise Reduction: Off
Flash Exposure Compensation: 0
Image Tone: Bright
Color Temperature: Not set
SR Result: stabilized
Shake Reduction (Setup): 7
Shutter Release Half Press Time: 4.25*sec
SR Focal length: 77*mm
Shutter Count: 2741
??? (0060): 0, 0, 0, 0
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??? (0067): 1
??? (0068): 1, 0
Dynamic Range Expansion: On
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High ISO Noise Reduction: 255
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Black Point: [129, 129, 129, 129]
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EV Steps: 1/3 EV steps
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Near Distance Abberation Correction Data (LC4): Not set
Light Color Aberration Correction Data (LC5): Not set
Open Aberration Data (LC6): Not set
AF Minimum Actuation Condition Data (LC7): Not set
Focal Length (LC8): 3.8*mm
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mv' nv' Data (LC10): 67
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??? (0208): 0x0
External Flash Exposure Comp: Not set (Off or Auto Modes)
External Flash Bounce: Not set
AE Metering Segment 1: 3.9*LV (center)
AE Metering Segment 2: 4*LV (center edge)
AE Metering Segment 3: 4.1*LV (upper, mid-right)
AE Metering Segment 4: 6.1*LV (upper, mid-left)
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AE Metering Segment 15: 5.3*LV (top)
AE Metering Segment 16: 7.1*LV (bottom)
Pentax Model: 0x12e76
Manufacture Date?: 2011-02-10
Camera has been serviced?: Serviced bit not set (Value: 2?)
Production ID?: 1
Internal Serial Number?: 45678
Power Source: 114 (Flag 7 set)
Battery States: Body Battery: 5; Grip Battery: 1
Battery A/D Body No Load: 2
Battery A/D Body Load: 158
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Matrix 8: [6766,*2689,*-1263], [-515,*9159,*-452], [1758,*384,*6050]
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AF Points Unknown 2?: Center, Bit 13?, Bit 14?
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AF Defocus: 2
AF Integration Time: 10*ms
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??? (0229): 4001462
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??? (03FF): , , , , , , //, , , , , , , ,
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