Pentax DSLR AF accuracy

Thank you for the informative post Wally.
--
Lance B
Lady Astor: 'Winston, you're drunk'
Winston Churchill: 'And you madam, are ugly, but tomorrow I'll be sober'
Lady Astor: 'Winston, if you were my husband, I would poison your tea!'
Winston Churchill: 'Madam, if you were my wife, I'd drink it!'
GMT +10hours

Wally OZ said:

I wish I had known about that adjustment I certainly would have
tried it with the D.

Click to expand...

A also adjusted my D70 manually Now it has almost perfect accuracy in any lighting conditions. But adjusting sub mirror has side effect of making top and bottom AF sensors slightly off the exact focusing point in different directions. Anyway I never use them. The pentax AF plate manual adjustment doesn't have that side effect. I know the D70 also has that 3 magic screws but they are too difficult to reach.

As to pentax the procedure is pretty stupid. Just rotate all 3 screws by the same amount using hexagonal driver 1.5 mm size. Clock wise rotation bring focus point closer to the camera (eliminating back focus). Take care - they are pretty sensitive - start from about 15 degree and look at the result.

I guess the istD has similar internal design but I had no chance to disassemble it.

Oleg_V said:

Wally OZ said:

I wish I had known about that adjustment I certainly would have
tried it with the D.

Click to expand...

A also adjusted my D70 manually Now it has almost perfect
accuracy in any lighting conditions. But adjusting sub mirror has
side effect of making top and bottom AF sensors slightly off the
exact focusing point in different directions. Anyway I never use

Click to expand...

Thanks Oleg, I also read that, I did test for it after the adjustment expecting errors on the other sensors but did not observe any, all seem to work accuratley, mind you the backfocus I was adjusting for was ever so slight, I think I turned the screw maybe 10 degrees at the most.

I never used the other sensors until recently, I find them useful for nearest object focus with the 400mm OS lens, with any luck I will be testing it on Sunday with the Airbus A380 landing in Sydney.

Oleg_V said:

them. The pentax AF plate manual adjustment doesn't have that side
effect. I know the D70 also has that 3 magic screws but they are
too difficult to reach.

Click to expand...

Do you have a pic of the D70 " magic screws", how difficult to reach?

Is that the reason even Nikon don't seem to fix it, i.e too hard.

Oleg_V said:

As to pentax the procedure is pretty stupid. Just rotate all 3
screws by the same amount using hexagonal driver 1.5 mm size. Clock
wise rotation bring focus point closer to the camera (eliminating
back focus). Take care - they are pretty sensitive - start from
about 15 degree and look at the result.

I guess the istD has similar internal design but I had no chance to
disassemble it.

Click to expand...

In your testing did you observe a difference with different lighting?

I am convinced daylight/shade is the only way to test focus.

Wally OZ said:

Do you have a pic of the D70 " magic screws", how difficult to reach?

Click to expand...

No. But I read service manuals for film AF bodies.

Wally OZ said:

Is that the reason even Nikon don't seem to fix it, i.e too hard.

Click to expand...

Recent nikon bodies have more accurate AF. Anyway service guys use completely different procedure for adjusting AF - via software configuration.

Wally OZ said:

In your testing did you observe a difference with different lighting?

Click to expand...

Yes - that was my point in the first post. Seems that its impossible to adjust AF correctly for any lighting and thats definitely the design flaw of pentax.

Oleg_V said:

Oleg_V said:

Do you have a pic of the D70 " magic screws", how difficult to reach?

Click to expand...

No. But I read service manuals for film AF bodies.

Oleg_V said:

Is that the reason even Nikon don't seem to fix it, i.e too hard.

Click to expand...

Recent nikon bodies have more accurate AF. Anyway service guys use
completely different procedure for adjusting AF - via software
configuration.

Click to expand...

I read posts to that effect, I assume the software has limits and seeing the mechanical adjustments, I presume the optics have to be correctly aligned before you can adjust the software, you can see many posts where the fault isn't fixed till it goes back second or third time, maybe they do the software fix and it has limits eventually they do both.

Oleg_V said:

Oleg_V said:

In your testing did you observe a difference with different lighting?

Click to expand...

Yes - that was my point in the first post. Seems that its
impossible to adjust AF correctly for any lighting and thats
definitely the design flaw of pentax.

Click to expand...

oops...I did read that but forgot..

Thanks for the very useful information.

Wally OZ said:

I read posts to that effect, I assume the software has limits and
seeing the mechanical adjustments, I presume the optics have to be
correctly aligned before you can adjust the software,

Click to expand...

Of cause you are right

Wally OZ said:

you can see
many posts where the fault isn't fixed till it goes back second or
third time, maybe they do the software fix and it has limits
eventually they do both.

Click to expand...

I noticed that the accuracy of AF testing using AF chart is generally not enough. Only shooting in real situation, analyzing the results and applying corrections one can obtain more or less perfect results. Thats why the AF adjustment via in camera menu would be an extremely useful.

Oleg_V said:

I noticed that the accuracy of AF testing using AF chart is
generally not enough. Only shooting in real situation, analyzing
the results and applying corrections one can obtain more or less
perfect results. Thats why the AF adjustment via in camera menu
would be an extremely useful.

Click to expand...

Now there's an excellent idea!! who is going to do it first, should be real easy to do, everything else can be adjusted at the moment so why not focus.

Hi Lance sorry I took so long to reply I was floored.

Are you planning on shooting the A380 on Sunday morning?

Wally OZ said:

Hi Lance sorry I took so long to reply I was floored.

Are you planning on shooting the A380 on Sunday morning?

Click to expand...

I wasn't as I didn't even know it was arriving, but I may have a look if I get the chance now that I know it is coming to Sydney. Where are you going to get your vantage point from and what time does it arrive?

--
Lance B
Lady Astor: 'Winston, you're drunk'
Winston Churchill: 'And you madam, are ugly, but tomorrow I'll be sober'
Lady Astor: 'Winston, if you were my husband, I would poison your tea!'
Winston Churchill: 'Madam, if you were my wife, I'd drink it!'
GMT +10hours

Wally OZ said:

Now there's an excellent idea!! who is going to do it first, should
be real easy to do, everything else can be adjusted at the moment
so why not focus.

Click to expand...

Hope DSLR developers also read the forum.

10 am Sunday coming from Brisbane, leaving Monday morning to go to Melbourne that's all I know.

I can't decide if I go to the little observation deck or hang around botany bay or one of the back streets of Marrickville/Sydenham as it goes overhead, but then I miss the landing, I will likley decide on the day depending on the weather.

I hope it does at least one touch and go and not just plonk itself on the ground.

http://www.sydneyairport.com.au/SACL/default.htm

http://www.thecouriermail.news.com.au/common/story_page/0,5936,16908716%255E1702,00.html

Ah you see, your eyes are focused on the focusing screen, where the image is being formed, so we are looking at what the sensor will see when it makes an exposure. The AF sensor, doesn't - and like mentioned here, has problems dealing with different wavelenghts. Our eyes don't.

RiceHigh said:

Not really, our eyes don't focus and we just see if the focused
image on the focusing screen is in-focus or not by judging the
sharpness viewed in the finder image. This requires all the
camera's optical alignment is accurate in the very first place.

Click to expand...

--
Richard with DS + DA 18-55, DA 50-200 @ +0800GMT
left-eyed photography - http://www.richx.org

Wally OZ said:

10 am Sunday coming from Brisbane, leaving Monday morning to go to
Melbourne that's all I know.

I can't decide if I go to the little observation deck or hang
around botany bay or one of the back streets of
Marrickville/Sydenham as it goes overhead, but then I miss the
landing, I will likley decide on the day depending on the weather.

Click to expand...

I would guarantee that the Obs deck will be packed with sightseers for the new plane!

The other vantage points are on Qantas Drive or near where the M5 tunnel meets The Grande Parade at Kyeemagh at the Cooks River mouth. Many a photographer has been spotted there.

To get to the car park, I think you have to come from the south along the Grande Parade and turn left into it from under the M5 overpass before you get to the tunnel under the airport runway. Is that clear?

Wally OZ said:

I hope it does at least one touch and go and not just plonk itself
on the ground.

Click to expand...

--
Lance B
Lady Astor: 'Winston, you're drunk'
Winston Churchill: 'And you madam, are ugly, but tomorrow I'll be sober'
Lady Astor: 'Winston, if you were my husband, I would poison your tea!'
Winston Churchill: 'Madam, if you were my wife, I'd drink it!'
GMT +10hours

Thanks for the links.

Wally OZ said:

http://www.sydneyairport.com.au/SACL/default.htm

http://www.thecouriermail.news.com.au/common/story_page/0,5936,16908716%255E1702,00.html

Click to expand...

--
Lance B
Lady Astor: 'Winston, you're drunk'
Winston Churchill: 'And you madam, are ugly, but tomorrow I'll be sober'
Lady Astor: 'Winston, if you were my husband, I would poison your tea!'
Winston Churchill: 'Madam, if you were my wife, I'd drink it!'
GMT +10hours

Lance B said:

Wally OZ said:

10 am Sunday coming from Brisbane, leaving Monday morning to go to
Melbourne that's all I know.

I can't decide if I go to the little observation deck or hang
around botany bay or one of the back streets of
Marrickville/Sydenham as it goes overhead, but then I miss the
landing, I will likley decide on the day depending on the weather.

Click to expand...

I would guarantee that the Obs deck will be packed with sightseers
for the new plane!

Click to expand...

Me thinks you are right, it could only hold about 100 persons max and then you wouldn't see much unless you are at the front, specially if it comes in over the Bay and parks on the side nearest the bay.

Lance B said:

The other vantage points are on Qantas Drive or near where the M5
tunnel meets The Grande Parade at Kyeemagh at the Cooks River
mouth. Many a photographer has been spotted there.
To get to the car park, I think you have to come from the south
along the Grande Parade and turn left into it from under the M5
overpass before you get to the tunnel under the airport runway. Is
that clear?

Click to expand...

I can find that Thanks, sounds like the best spot.

Wally OZ said:

Lance B said:

Wally OZ said:

10 am Sunday coming from Brisbane, leaving Monday morning to go to
Melbourne that's all I know.

I can't decide if I go to the little observation deck or hang
around botany bay or one of the back streets of
Marrickville/Sydenham as it goes overhead, but then I miss the
landing, I will likley decide on the day depending on the weather.

Click to expand...

I would guarantee that the Obs deck will be packed with sightseers
for the new plane!

Click to expand...

Me thinks you are right, it could only hold about 100 persons max
and then you wouldn't see much unless you are at the front,
specially if it comes in over the Bay and parks on the side nearest
the bay.

Wally OZ said:

The other vantage points are on Qantas Drive or near where the M5
tunnel meets The Grande Parade at Kyeemagh at the Cooks River
mouth. Many a photographer has been spotted there.
To get to the car park, I think you have to come from the south
along the Grande Parade and turn left into it from under the M5
overpass before you get to the tunnel under the airport runway. Is
that clear?

Click to expand...

I can find that Thanks, sounds like the best spot.

Click to expand...

Just a thought. Another spot is near the container terminal but I can't remember the name of the road. Suffice to say is that you go right to the end of the Port Botany road and turn right along Bunnerong Road(I think) and then turn right again which takes you down behind the Port Botany container terminal. You can then get the plane landing from over Kurnell if it is coming in from that direction. It will depend on the wind of the day I guess. They normally land and take off into the wind, so if there is a north or north wester they will most probably come in over the Bay.

--
Lance B
Lady Astor: 'Winston, you're drunk'
Winston Churchill: 'And you madam, are ugly, but tomorrow I'll be sober'
Lady Astor: 'Winston, if you were my husband, I would poison your tea!'
Winston Churchill: 'Madam, if you were my wife, I'd drink it!'
GMT +10hours

Thanks Lance, I know where you mean, I don't know the name of the roads either, are you going to go down on Sunday, I can listen in to the air traffic control but if the winds a light and variable they may not even stick to normal procedures [land in opposite direction to previous traffic] so it will be left to some very quick decisions [on my part] at the last minute when I hear what instructions they are given that may only give me 5 minutes to move to another position and that is not enough as we both know.

My guess is that if winds allow they will be coming in over gladesville to show it off to as many people as possible.

Wally, thanks for the exhaustive comments. I also read yesterday the other thread about different light wavelengths and am kicking myslef for not considering it previosuly. So obvious it makes me laugh! If it were not for the fact I am a reluctant pixel peeper I would re-test my Sigma 70-200/2.8 which was previous rested under tungsten and fluro (I now realise) and got a couple of inconsistent results using that D70 test chart of the net (45 degree shooting one).

In the end and at the request of Richard Day I went out shooting real world shots of subjects at f/2.8 and a variety of focal lengths. Be damned if I can pick FF but if it is it might be as you suggest, rear edge of focus ay f/2.8 sits on the subject perhaps -- since in the normal world I like "one stop down" are you going to see it? No. Anyway, pretty much done with trying to prove there is a porblem as it never affects what I do (unlike Richard's Sigma 100-300 EX which backfocused into the next universe!)

Also thanks for the reminder on the A380 - I knew it was coming but somehow I forgot when, I might just slip out to one of those spots for a gecko and indulge my flying interest for a while (some of the members of this forum are off to NZ for the 'Warbirds over Wanaka' next Easter -- I'd love to be one of them since I missed Avalon again...)

Regards,

--
Brett



The Journey is the Thing

The A380 may be arriving earlier and do a fly over sydney harbour, found this at

http://www.asiatraveltips.com/news05/1111-A380.shtml

While times are subject to change, the current schedule (local times) for the A380's Australian visit is:

Saturday 12 November - 8:00am Arrive Brisbane

Sunday 13 November
6:00am Depart Brisbane
8:30am Flyover Sydney Harbour for Qantas aerial photography (weather permitting)
9:10am (approx) Arrive Sydney

Monday 14 November
11:15am Depart Sydney
12:30pm (approx) Arrive Melbourne

Funny how information in Australia is so vague about this, last night's ABC news said it is comming next week!! I actually phoned them in case there was a genuine change of plans as it is already delayed with engine changes, , got through to the ABC news room and asked if that was correct and I got an "OH S* T !! did we say that??, oh hell the news is over we must correct that, that's wrong."

Brett St Pierre said:

Wally, thanks for the exhaustive comments. I also read yesterday
the other thread about different light wavelengths and am kicking
myslef for not considering it previosuly. So obvious it makes me
laugh! If it were not for the fact I am a reluctant pixel peeper I
would re-test my Sigma 70-200/2.8 which was previous rested under
tungsten and fluro (I now realise) and got a couple of inconsistent
results using that D70 test chart of the net (45 degree shooting
one).

Click to expand...

Same here the penny just didn't drop, I have known since January that the tests had to be done outdoors just didn't realise wht it means, I posted my info lots of times, most people just ignored it and kept complaining,

Of course it varies, we have simply forgotten what we alreardy knew, our old lenses used to have a RED R, of course it varies and not just with IR.

Brett St Pierre said:

In the end and at the request of Richard Day I went out shooting
real world shots of subjects at f/2.8 and a variety of focal
lengths. Be damned if I can pick FF but if it is it might be as you
suggest, rear edge of focus ay f/2.8 sits on the subject perhaps --
since in the normal world I like "one stop down" are you going to
see it? No. Anyway, pretty much done with trying to prove there is

Click to expand...

It is only at 200mm 2.8 by f4 it is exactly as it should be, the 70mm end is not affected, it starts to kick in past 100mm, not certain about the exact spot, another thing I have forgotten

Brett St Pierre said:

a porblem as it never affects what I do (unlike Richard's Sigma
100-300 EX which backfocused into the next universe!)

Click to expand...

People rave about the 100-300 EX oh well, sorry to hear that, Richard din't need that.

Brett St Pierre said:

Also thanks for the reminder on the A380 - I knew it was coming but
somehow I forgot when, I might just slip out to one of those spots
for a gecko and indulge my flying interest for a while (some of the
members of this forum are off to NZ for the 'Warbirds over Wanaka'
next Easter -- I'd love to be one of them since I missed Avalon
again...)

Click to expand...

I promised myslef next time to go to Avalon, when is it on next?

Brett St Pierre said:

Regards,

--
Brett



The Journey is the Thing

Click to expand...