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03-17-2011, 04:36 AM   #106
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QuoteOriginally posted by Ray Pulley Quote
The K5 was here when I got home this evening, so I ran a few tests.
I just noticed a potential issue with your shots:
The focus target (on the LHS) seems to be the sharpest when the ruler is indicating backfocus. I'm assuming you used exactly the same (embossing + sharpening) processing on all shots. Probably that assumption is wrong as the contrast in the DOF in the last shot is not as high as in the earlier shots.

Furthermore, the focus target doesn't seem to be aligned to the camera. It seems to show a "yaw" rotation. The RHS of the target gradually goes out of focus. Is that just a post-processing effect? It seems to be uneven comparing the top with the bottom of the focus target.

If the LensAlign tool really had a "yaw" rotation w.r.t. to the sensor plane than the FF/BF read outs will be wrong (the above two observations regarding focus target sharpness and yaw rotation are consistent with each other).

A focus target which is not in perfect alignment may facilitate erratic focusing.

I would have thought that the alignment aids of the LensAlign tool would rule out such errors. Could you please check whether there is any merit to my observations (e.g., rerun the tests with another alignment)?


Last edited by Class A; 03-17-2011 at 04:44 AM.
03-17-2011, 04:45 AM   #107
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Yes

QuoteOriginally posted by Tommot1965 Quote
nice one Ray..great test mate..

any chance you could test a wider FL..say 16-17 FL...at 2.8
I have a lot of lenses to check, several of which are wides. My workhorse is the 16-50 f2.8, so that will be a priority.

I also have a DA15 to check.

Note that zooms will likely only be corrected at one focal length. I normally would set the 16-50 at 50mm so I can use the same test setup as the FA 50, but it that is not where I use it most, so it makes sense to test it at several settings and see where the best compromise adjustment is.

Ray
03-17-2011, 04:47 AM   #108
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Worrisome

QuoteOriginally posted by Gimbal Quote
The performance of the 1.03 seems to be very inconsistent. At first I thought it was a big improvement, a couple of days later I'm not so sure. It still seems to front focus a lot in real usage.
The odd behavior was worrisome. I will have to see how it performs in more real life shots.

Ray
03-17-2011, 04:48 AM   #109
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QuoteOriginally posted by Class A Quote
Great test, Ray, thanks!


That is a bit disconcerting but I wonder if the FA 50/1.4 plays a part in this. It is one of the few lenses my K100D often hesitates to lock correct focus.

Was it really problem free without AF adjustments? If we can confirm a difference in behaviour regarding AF adjustments vs no adjustments that would very much point to a bug to me (as long as the adjustments are moderate).
It was consistently BF. I have the series but only looked at them. I will look again when I get a chance.

Ray

03-17-2011, 04:51 AM   #110
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good stuff Ray

Im interested as My 17-50 doesn't seem to like much before 35mm in Low light..might be me/lens/camera..or a combination of all three...
03-17-2011, 05:08 AM   #111
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QuoteOriginally posted by Class A Quote
I just noticed a potential issue with your shots:
The focus target (on the LHS) seems to be the sharpest when the ruler is indicating backfocus. I'm assuming you used exactly the same (embossing + sharpening) processing on all shots. Probably that assumption is wrong as the contrast in the DOF in the last shot is not as high as in the earlier shots.

Furthermore, the focus target doesn't seem to be aligned to the camera. It seems to show a "yaw" rotation. The RHS of the target gradually goes out of focus. Is that just a post-processing effect? It seems to be uneven comparing the top with the bottom of the focus target.

If the LensAlign tool really had a "yaw" rotation w.r.t. to the sensor plane than the FF/BF read outs will be wrong (the above two observations regarding focus target sharpness and yaw rotation are consistent with each other).

A focus target which is not in perfect alignment may facilitate erratic focusing.

I would have thought that the alignment aids of the LensAlign tool would rule out such errors. Could you please check whether there is any merit to my observations (e.g., rerun the tests with another alignment)?

A couple of notes:

I forgot to add that the target distance was 25x FL and the background was a black backdrop. There are no ther light sources in the room.

The FA 50 @ f1.4 is SOFT wide open, or at least my copy is. Frankly, I have no idea how the camera gets a good lock in low light wide open given what I have seen when testing at 1.4.

Because of this, I was boosting the contrast in PP to show the focus zone more clearly. I forgot to do so on the last shot which is the bottom in the image above. Other than de-saturating, no there PP was apllied. The shots were jpg out of the camera at default settings.

As I mentioned in an earlier post, I do not have an optical bench, and in this case the test is performed on two tripods. Alignment is done by the little hole in the center of the target. It is hard to see in these shots, but using more light, you simply center the hole in the rear of the fixture (which is smaller and surrounded by red) in the hole in the front. This is done by looking at an image, so it is not 100% foolproof.

While it is probably possible to get better alignment, I see no practical purpose in doing so and do not think there would be any improvement in real world shooting. Also, in this case it is not at all necessary to highlight the difference in the focus point chosen by the camera before and after 1.03 was applied.

Lastly, these are hand crops done on my laptop in the room where I was testing, so there is no doubt some difference in how I cropped them. This will not affect the focus zone, of course, but could show minor differences in the size or even rotation of the cropped image. It is even possible for a small difference in aligment to creep in from flipping the MF lever and focusing the lens to infinity between shots.

At the end of the day, the prrof is in shooting, which is most often done handheld in far worse conditions than this, so worrying over small veriances in tests like these will just drive you crazy

Ray
03-17-2011, 05:40 AM   #112
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QuoteOriginally posted by Class A Quote
I just noticed a potential issue with your shots:
The focus target (on the LHS) seems to be the sharpest when the ruler is indicating backfocus. I'm assuming you used exactly the same (embossing + sharpening) processing on all shots. Probably that assumption is wrong as the contrast in the DOF in the last shot is not as high as in the earlier shots.

Furthermore, the focus target doesn't seem to be aligned to the camera. It seems to show a "yaw" rotation. The RHS of the target gradually goes out of focus. Is that just a post-processing effect? It seems to be uneven comparing the top with the bottom of the focus target.

If the LensAlign tool really had a "yaw" rotation w.r.t. to the sensor plane than the FF/BF read outs will be wrong (the above two observations regarding focus target sharpness and yaw rotation are consistent with each other).

A focus target which is not in perfect alignment may facilitate erratic focusing.

I would have thought that the alignment aids of the LensAlign tool would rule out such errors. Could you please check whether there is any merit to my observations (e.g., rerun the tests with another alignment)?

FYI -

The lensalign is made up of die-cut parts that look like a thin foamcore material. The parts simply snap into grooves and tabs, so one should not kid themselves that we have any sort of optical lab quality fixture here.

There is no way to know exactly how square the rear panel is to the front, or exactly how square the ruler is to the rest of the fixture, or more importantly, how square the ruller is to the alignment hole arrangement. They look ok, but there could well be some mis-alignment in all of these parts. I would be shocked if there wasn't.

The main point is that it is far better than a paper taped to a table or folded up at an angle where you cannot even start to know how well everything is aligned.

I try to not get wrapped around the axle over these level of details because it really isn't going to make any difference in the real world.

Ray
03-17-2011, 08:42 PM   #113
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QuoteOriginally posted by Ray Pulley Quote
The FA 50 @ f1.4 is SOFT wide open, or at least my copy is.
All copies are.

QuoteOriginally posted by Ray Pulley Quote
Frankly, I have no idea how the camera gets a good lock in low light wide open given what I have seen when testing at 1.4.
The AF system doesn't "see" at f/1.4. The standard AF aperture is f/5.6, some cameras have more sensitive, f/2.8 centre AF areas.


QuoteOriginally posted by Ray Pulley Quote
Other than de-saturating, no there PP was apllied.
Looks like an "emboss" filter to me.

QuoteOriginally posted by Ray Pulley Quote
It is hard to see in these shots, but using more light, you simply center the hole in the rear of the fixture (which is smaller and surrounded by red) in the hole in the front.
I trust that you closed the sighting gate before taking the shots. The red dot should only be visible during the initial alignment phase.

QuoteOriginally posted by Ray Pulley Quote
At the end of the day, the prrof is in shooting, which is most often done handheld in far worse conditions than this, so worrying over small veriances in tests like these will just drive you crazy
Well, if you refer to hand holding as an argument you might as well not calibrate your lenses.
Seriously though, I agree that in your particular case the firmware effect seems to be big enough that minor alignment issues may not play a role. However, in general "AF fine adjustments" are done to get the last bit of performance out of the AF system. If the adjustment values are found by reading out the FF/BF on a ruler whose "0" mark is not exactly in the same plane as the focus target then one doesn't get optimal results.

QuoteOriginally posted by Ray Pulley Quote
The lensalign is made up of die-cut parts that look like a thin foamcore material. The parts simply snap into grooves and tabs, so one should not kid themselves that we have any sort of optical lab quality fixture here.
Oh no. This kills any doubts I had about getting the tool out of laziness. What is the exact model name for the version you have? It comes in all sorts of variants and you seem to have one that can be disassembled for transport.

QuoteOriginally posted by Ray Pulley Quote
The main point is that it is far better than a paper taped to a table or folded up at an angle where you cannot even start to know how well everything is aligned.
Actually, I have to disagree. With a paper taped to a table you don't need any accuracy regarding the 45 angle of the camera (camera pitch) to the table unless you want the markings on the focusing chart to translate into a known distance. Camera roll and yaw are easy to control with markings in the viewfinder by aligning them to the focus target (this implies reliance on the viewfinder alignment but the supremely thorough among us can verify the alignment when looking at the final images).

If the focus chart has a "roll" or "pitch" rotation, you'll recognise it by the fact that the FF/BF will be different on the RHS vs the LHS. If they are both the same, the focus chart is well aligned.

The big advantage of a paper focus chart is that there is no doubt that the focus target and the read out position are in the same plane (given good alignment). If your LensAlign tool is warped this is not true and you'll get rather useless readouts.

QuoteOriginally posted by Ray Pulley Quote
I try to not get wrapped around the axle over these level of details because it really isn't going to make any difference in the real world.
Well, I think it can make a difference. I understand that you don't want to go overboard but if "about right" is good enough then one doesn't really need a LensAlign tool. Cheaper solutions are just fine in this case.

03-17-2011, 10:32 PM - 1 Like   #114
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Agree to Disagree

QuoteOriginally posted by Class A Quote
All copies are.


The AF system doesn't "see" at f/1.4. The standard AF aperture is f/5.6, some cameras have more sensitive, f/2.8 centre AF areas.
f2.8 sensors would not be closer to the center. They would be closer to the edges of the lens, which would be necessary for use in an f2.8 lens because it has a larger diameter than an f5.6 lens (focal length being equal). They may or may not be more sensitive, but they would have a larger base distance to use in computing the focus solution, which would make for a more accurate calculation.

Pentax positions the AF sensors at a diameter near the size that corresponds to f5.6 so that slower lenses will AF. Otherwise, if the sensors were positioned at a diamater that equated to f2.8 they would simply be blocked when a lens slower than f2.8 is used because there would be no glass out there on a f5.6 lens to gather any light from.

QuoteQuote:
Looks like an "emboss" filter to me.
You mentioned sharpening. No sharpening was applied other than whatever default the camera applied.


QuoteQuote:
I trust that you closed the sighting gate before taking the shots. The red dot should only be visible during the initial alignment phase.
Nope. No such gate.


QuoteQuote:
Well, if you refer to hand holding as an argument you might as well not calibrate your lenses.
In that case, Pentax need not calibrate them either


QuoteQuote:
Seriously though, I agree that in your particular case the firmware effect seems to be big enough that minor alignment issues may not play a role. However, in general "AF fine adjustments" are done to get the last bit of performance out of the AF system. If the adjustment values are found by reading out the FF/BF on a ruler whose "0" mark is not exactly in the same plane as the focus target then one doesn't get optimal results.
I find that in many cases an adjustment of 1 either way at f1.4 will not get a perfectly centered focus adjust. This is irrelevant in real world use.


QuoteQuote:
Oh no. This kills any doubts I had about getting the tool out of laziness. What is the exact model name for the version you have? It comes in all sorts of variants and you seem to have one that can be disassembled for transport.
The model is embossed into the pics above.


QuoteQuote:
Actually, I have to disagree. With a paper taped to a table you don't need any accuracy regarding the 45 angle of the camera (camera pitch) to the table unless you want the markings on the focusing chart to translate into a known distance.
I would start with the fact that focusing on a point at an angle is a basic flaw in this method. The paper methods I have seen (and used) are also far too close to the target. There are other issues with your method, but you are happy, so that is fine.


QuoteQuote:
Camera roll and yaw are easy to control with markings in the viewfinder by aligning them to the focus target (this implies reliance on the viewfinder alignment but the supremely thorough among us can verify the alignment when looking at the final images).
QuoteQuote:
If the focus chart has a "roll" or "pitch" rotation, you'll recognise it by the fact that the FF/BF will be different on the RHS vs the LHS. If they are both the same, the focus chart is well aligned.

The big advantage of a paper focus chart is that there is no doubt that the focus target and the read out position are in the same plane (given good alignment). If your LensAlign tool is warped this is not true and you'll get rather useless readouts.
Sorry, you are going to have a hard time convincing me that something you taped to your kitchen table has a high degree of accuracy..

QuoteQuote:
Well, I think it can make a difference. I understand that you don't want to go overboard but if "about right" is good enough then one doesn't really need a LensAlign tool. Cheaper solutions are just fine in this case.
You talk like you would only be happy with a true optical bench test setup, but then are perfectly happy taping a piece of paper to some (maybe) flat surface and pointing your camera at it on a tripod. I find the disconnect rather odd.

Ray
03-18-2011, 12:45 AM   #115
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Ray


stop answering Posts and get on with that wide FL test....
03-18-2011, 01:42 AM   #116
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QuoteOriginally posted by Ray Pulley Quote
f2.8 sensors would not be closer to the center.
I didn't say that. No further comments.

QuoteOriginally posted by Ray Pulley Quote
No sharpening was applied other than whatever default the camera applied.
You could have just admitted that your "Other than de-saturating, no there PP was apllied." comment was wrong. No further comment.

QuoteOriginally posted by Ray Pulley Quote
In that case, Pentax need not calibrate them either
Well yes, but Pentax doesn't say that hand-holding invalidates all precision adjustments anyhow.

QuoteOriginally posted by Ray Pulley Quote
The model is embossed into the pics above.
Thanks.

QuoteOriginally posted by Ray Pulley Quote
I would start with the fact that focusing on a point at an angle is a basic flaw in this method.
Rest assured it isn't; not for the levels of accuracy you are aspiring to. I could point you to an explanation as to an angled chart works but, frankly, I sense from your tone that you made up your mind anyhow, that I somehow must offended you or someone you like, and that I could spend all day without getting through to you. I don't know how I earned your disrespect but you are of course entitled to your opinion.

QuoteOriginally posted by Ray Pulley Quote
Sorry, you are going to have a hard time convincing me that something you taped to your kitchen table has a high degree of accuracy..
True, but maybe that's neither my fault nor the fault of the method. It is your choice if you don't want to add to your knowledge.
03-18-2011, 05:34 AM   #117
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QuoteOriginally posted by Class A Quote
I didn't say that. No further comments.
It is clear that you do not understand this, so I can see why you would not comment. BTW, I would advise looking up the definition of "centre", which you used in describing the more "sensitive" f2.8 AF points.




QuoteQuote:
Rest assured it isn't; not for the levels of accuracy you are aspiring to. I could point you to an explanation as to an angled chart works but, frankly, I sense from your tone that you made up your mind anyhow, that I somehow must offended you or someone you like, and that I could spend all day without getting through to you. I don't know how I earned your disrespect but you are of course entitled to your opinion.
You are far too sensitive, but it is also clear that you have no interest in anything but your own opinion, so I will not point you to the counter explanations why your angled chart method has flaws.

QuoteQuote:
It is your choice if you don't want to add to your knowledge.
Thanks Yoda....

Ray

Last edited by Ray Pulley; 03-18-2011 at 05:50 AM.
03-18-2011, 06:08 AM   #118
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Ray, for the benefit of other readers of this thread, this will be the last time I'll respond to an ad hominem argument.

QuoteOriginally posted by Ray Pulley Quote
It is clear that you do not understand this, so I can see why you would not comment. BTW, I would advise looking up the definition of "centre", which you used in describing the more "sensitive" f2.8 AF points.
What I meant was that cameras with f/2.8 AF areas, have them located in the centre of the viewfinder. Do you know any camera that has an off-centre AF area with sensitivity higher than f/5.6? (In the sense that the user can select an AF area that is not the centre AF area in the middle of the frame but still has sensitivity better than f/5.6.) If I'm not commenting than because I don't think this is leading anywhere, not because I don't have the technical background. I'm happy to be patient, but not if I sense that they other party has no interest in a mutual knowledge exchange.

QuoteOriginally posted by Ray Pulley Quote
You are far too sensitive, but it is also clear that you have no interest in anything but your own opinion, so I will not point you to the counter explanations why your angled chart method has flaws.
Maybe I overreacted, I can see that. But if my assumptions had no basis then why didn't you post your counter explanations nevertheless? BTW, I'll sleep well at night because I'd be very surprised if you could come up with a substantial argument against angled charts. Please, by all means, surprise me. It would help us all.

QuoteOriginally posted by Ray Pulley Quote
Thanks Yoda....
I take that as a compliment.
03-18-2011, 06:11 AM   #119
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We Have Gotten Off Topic

QuoteOriginally posted by Class A Quote
Ray, for the benefit of other readers of this thread, this will be the last time I'll respond to an ad hominem argument.


What I meant was that cameras with f/2.8 AF areas, have them located in the centre of the viewfinder. Do you know any camera that has an off-centre AF area with sensitivity higher than f/5.6? If I'm not commenting than because I don't think this is leading anywhere, not because I don't have the technical background. I'm happy to be patient, but not if I sense that they other party has no interest in a mutual knowledge exchange.


Maybe I overreacted, I can see that. But if my assumptions had no basis then why didn't you post your counter explanations nevertheless? BTW, I'll sleep well at night because I'd be very surprised if you could come up with a substantial argument against angled charts. Please, by all means, surprise me. It would help us all.


I take that as a compliment.
We are getting far afield from the original topic, so let's just leave it at that.

I do apologize if you felt dis-respected.

Thanks,

Ray
03-18-2011, 06:39 AM   #120
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QuoteOriginally posted by Ray Pulley Quote
I do apologize if you felt dis-respected.
And I apologise for overreacting.
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