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01-16-2008, 10:11 AM   #1
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Two ways to adjust focus?????

OK, I'm a little confused. I've come across two different threads - both here and on DPReview - that show two different ways to adjust focus on the Pentax DSLRs - one way is mechanical via the screws on the bottom and the other way is electronic via the service menus.

Are these two different ways to achieve the same objective - fix back or front focus issues? Or do they actually have different purposes or outcomes??

And the funny thing is yhat I don't even know if my DS even has a focus problem.

01-16-2008, 10:19 AM   #2
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There is currently no way to adjust the camera to fix front or back focus issues yourself. I don't know what you're talking about. Can you link to the threads you reference?
01-16-2008, 10:27 AM   #3
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The firs way you mentioned I've never heard of so I will not reccomend it.

The second way was in Firmware v1.10 Pentax left the debug mode in the camera and with a few presses of buttons you could access it and repair your front and back focus issues.
01-16-2008, 10:31 AM   #4
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QuoteOriginally posted by codiac2600 Quote
The second way was in Firmware v1.10 Pentax left the debug mode in the camera and with a few presses of buttons you could access it and repair your front and back focus issues.
I thought I'd read with this method the setting is lost after turning off the camera (which didn't make much sense, but I didn't read that countered)?

01-16-2008, 10:51 AM   #5
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confused about the camera model

QuoteOriginally posted by ChipB Quote
OK, I'm a little confused. I've come across two different threads - both here and on DPReview - that show two different ways to adjust focus on the Pentax DSLRs - one way is mechanical via the screws on the bottom and the other way is electronic via the service menus.

Are these two different ways to achieve the same objective - fix back or front focus issues? Or do they actually have different purposes or outcomes??

And the funny thing is yhat I don't even know if my DS even has a focus problem.
What was being discussed was, on the K10D (not the *ist Ds) when using firmware 1.1 - someone got the secret button sequence to get the camera into debug mode. Debug mode allows techs to modify, adjust, tune etc. the performance of the camera. In this case it was a way to fine tune the AF system.

When Pentax got wind of this - they came out with firmware 1.2 and they changed the seceret code. Then they came out with firmware 1.3 which allowed for the new lenses to focus using the in lens motors. Sort of "you want to use the latest lenses? You have to give up the 'secret' code."

If you are using a *ist Ds - then this discussion is meaningless for you since that model is on firmware 2.02.

The Elitiist - formerly known as PDL
01-16-2008, 11:00 AM   #6
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Hers's a link to the "electronic" way to adjust focus on the *ist series of DSLRs: self focus adjust for dl,ds,ds2,k100d. [Page 1]: Pentax SLR Talk Forum: Digital Photography Review Note that this includes the DS (which I own) and I've confirmed on my camera that this menu sequence exists.

Here's the link to the "mechanical" way: I have fixed my front focus problem - how to [Page 1]: Pentax SLR Talk Forum: Digital Photography Review

So, back to my original question - what's the actual results difference??
01-16-2008, 03:59 PM   #7
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OK

QuoteOriginally posted by ChipB Quote
Hers's a link to the "electronic" way to adjust focus on the *ist series of DSLRs: self focus adjust for dl,ds,ds2,k100d. [Page 1]: Pentax SLR Talk Forum: Digital Photography Review Note that this includes the DS (which I own) and I've confirmed on my camera that this menu sequence exists.

Here's the link to the "mechanical" way: I have fixed my front focus problem - how to [Page 1]: Pentax SLR Talk Forum: Digital Photography Review

So, back to my original question - what's the actual results difference??
I stand corrected - about the *ist Ds at least. Now to your question:

Since I am not about to take my cameras apart - here is what I think.
The firmware method should only change how the AF sensor determines if an object is in focus. The AF sensor(s) are located in the bottom of the light box - light is guided to the sensors through half - silver mirror elements in the mirror is self. So the firmware "changes" how the AF subsystem determines what is in focus.

The "Hardware" fix is actually moving the sensor to get it perpendicular to the light going through the lens. This is more of a manufacturing variablility control - and it is physically moving the sensor.

I would suggest that you do a test --- only if you can consistently see bad things happening -- and send it back to Pentax to get fixed. If you take it on yourself - be prepared to face the potential of screwing things up royally and only being able to blame the guy in the mirror.

This leads to another question that I have - When people state they have FF/BF issues - just what "mode" are they using? On my *ist Ds when I --- wait for it --- READ THE MANUAL, it stated that if you are in Portrait mode - the subject would be the point in focus (dead center in DOF). When in Landscape mode - the forground would be OOF and the background would be adjusted to fall within the DOF. Same for macro mode - forground in focus - backgrounde OOF. In P or Green mode - the camera would decide (based on focus distance) what f:stop to pick - and maybe adust the focus to be a little off of what the distance scale should be?

I will leave it up to the measurbaters to hash this out. I de-coupled AF from the shutter button and have not moved off of AV for several years now. If you let the camera make all the decisions - well you get the idea. Take control - it is quite liberating.

Oh - no issues with BF/FF on either camera (*ist Ds and K10D).

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01-16-2008, 04:06 PM   #8
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QuoteOriginally posted by PDL Quote
I stand corrected - about the *ist Ds at least. Now to your question:

Since I am not about to take my cameras apart - here is what I think.
The firmware method should only change how the AF sensor determines if an object is in focus. The AF sensor(s) are located in the bottom of the light box - light is guided to the sensors through half - silver mirror elements in the mirror is self. So the firmware "changes" how the AF subsystem determines what is in focus.

The "Hardware" fix is actually moving the sensor to get it perpendicular to the light going through the lens. This is more of a manufacturing variablility control - and it is physically moving the sensor.

I would suggest that you do a test --- only if you can consistently see bad things happening -- and send it back to Pentax to get fixed. If you take it on yourself - be prepared to face the potential of screwing things up royally and only being able to blame the guy in the mirror.

This leads to another question that I have - When people state they have FF/BF issues - just what "mode" are they using? On my *ist Ds when I --- wait for it --- READ THE MANUAL, it stated that if you are in Portrait mode - the subject would be the point in focus (dead center in DOF). When in Landscape mode - the forground would be OOF and the background would be adjusted to fall within the DOF. Same for macro mode - forground in focus - backgrounde OOF. In P or Green mode - the camera would decide (based on focus distance) what f:stop to pick - and maybe adust the focus to be a little off of what the distance scale should be?

I will leave it up to the measurbaters to hash this out. I de-coupled AF from the shutter button and have not moved off of AV for several years now. If you let the camera make all the decisions - well you get the idea. Take control - it is quite liberating.

Oh - no issues with BF/FF on either camera (*ist Ds and K10D).

The Elitist - formerly known as PDL

Food for thought. when you say for portrait mode the focus point is in the center of the focus range, this means the camera front focuses, because depth of field in terms of distance is 1/3 in front 2/3 behind the pointof critical focus.

are we really talking about a deliberate setting here?

01-16-2008, 06:07 PM   #9
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All existing Pentax DSLRs can be calibrated the hardware or software way. Ideally, the actual phyical AF sensor module would be calibrated precisely 100%. But in reality, this is often impossible, especially with the cheap labour and lousy QC these days, the software way is employed to do any fine tuning and is much easier than the hardware way. But still, it is best to get the actual AF sensor as precise as possible to avoid any potential FF/BF issue. With the DS, you can still enter the debug mode with the latest 2.02 FW. But if you don't see any problem, better leave it as is.
01-16-2008, 06:28 PM   #10
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More Food

QuoteOriginally posted by Lowell Goudge Quote
Food for thought. when you say for portrait mode the focus point is in the center of the focus range, this means the camera front focuses, because depth of field in terms of distance is 1/3 in front 2/3 behind the pointof critical focus.

are we really talking about a deliberate setting here?
OK - here goes major speculation:

When the camera is in some "specific" mode - I am using landscape - portrait - and macro - those modes make assumptions as to what the user wants in focus. Since you have told the camera - by picking a mode or in the P or Green functions - the camera is assuming that you want certain portions of the image to be emphasised.

Now I was raised during a time when images had three basic parts - forground - middle ground and background. When using these "modes" the camera is emphasising a certain 'ground' to be the area of interest. e.g.
Macro -- forground in focus - the edge of the middle ground is the focus point - so AF (since it knows the f:stop) tends to FF - thereby throwing the background OOF and at the rear edge of DOF.
Portrait -- forground not all that important - background OOF. AF knowns the subject needs DOF to be dead center at the focal point - so the AF system sets the focus to maximize the DOF at the focal point.
Landscape -- background is the primary subject - forground to be ignored - middle ground less so. AF subsystem moves the focus to have the DOF contain all of the background.

All of this would be easier to visuallize if the d*mn lenses had DOF scales on them. I used to do this on purpose when shooting with my manual 35mm SLR. I think it is interesting to note that all of the so called "test" images I have seen are shot with wide open lenses where the DOF is a few millimeters.

Now let me be clear - this is mostly speculation on my part - as I do not measurebate - nor do I shoot "modes" anymore. I did that for the first week or so with my *ist Ds - within 6 months I was shooting 99.999% in AV, with a de-coupled AF (OK on the *ist Ds) and using RAW. When I started reading about BF/FF I took a look and could not see a problem with my camera. When I got my K10D, the same thing - in fact it has never had its shutter tripped in "Green" mode. I am not bragging - it is just something I do not use - I am the photographer - I want to be in control.

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01-16-2008, 06:35 PM   #11
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I have major back-focusing problems with my k10d, it shows up especially when using large apertures on glass longer than 50mm.. Since fast glass in the tele range is so damned expensive, I rarely see the problem

I'm not joking, it is a problem but, I've managed to deal with it. I know where to put the focusing ring in relation to what I see in my viewfinder for my most used glass. It only ever bites me when I slap on some chunk I don't use often.
01-16-2008, 06:52 PM   #12
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QuoteOriginally posted by Tom M Quote
I have major back-focusing problems with my k10d, it shows up especially when using large apertures on glass longer than 50mm.. Since fast glass in the tele range is so damned expensive, I rarely see the problem

I'm not joking, it is a problem but, I've managed to deal with it. I know where to put the focusing ring in relation to what I see in my viewfinder for my most used glass. It only ever bites me when I slap on some chunk I don't use often.
Again, I ask when you say back focusing is this because you expect the center (distance wise) to be equal front and back of the focus point? in reality it isnt, it should be as I stated earlier 1/3 front 2/3 back. This is why I raised the point. Are we expecting something that is not within the rules of optical physics?
01-16-2008, 10:54 PM   #13
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QuoteOriginally posted by ChipB Quote
So, back to my original question - what's the actual results difference??
I have made this adjustment via service menu on my K100D, and yes it does correct any bf/ff. Trouble is if you have problem with only one lens and you adjust the camera, what's going to happen when you use the other no-problem lenses?

Hence I changed it back to neutral.
01-17-2008, 11:31 AM   #14
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Sorry, haven't meant to ignore a thread I started.

Thanks to all for your comments about this - definately food for thought. Sounds like there's as many for as against doing anything. For those of us on a *very* tight budget (I'm retired - the words "fixed income" mean a LOT more now) whose cameras are out of warranty, either of these methods could fix or alleviate a bothersome issue.

Note, I'm not promoting either of these - I just hadn't seen them together so pros and cons of them individually or collectively could be discussed.
01-17-2008, 12:09 PM   #15
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Sorry, haven't meant to ignore a thread I started.

Thanks to all for your comments about this - definately food for thought. Sounds like there's as many for as against doing anything. For those of us on a *very* tight budget (I'm retired - the words "fixed income" mean a LOT more now) whose cameras are out of warranty, either of these methods could fix or alleviate a bothersome issue.

Note, I'm not promoting either of these - I just hadn't seen them together so pros and cons of them individually or collectively could be discussed.
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