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Landscape mode infinty default-focus
- Thread starter ga-ga
- Start date
)ga-ga
Senior Member
Hi Ian,
Thanks for coming in.....
I'm only just getting to analyse the pics myself -
thought I'd post em first for everybody to muse over........
while I just had dinner....
I think at least one is a red-herring.........
I think Chevron 70 is locked on the fir trees (or one branch) and so not properly focused on the Chevrons.....
see if you can come to logical conclusions without that one.........
my understanding of the 1.5x is 1.5 times the focal length......
thats by firm belief unless anybody wants to convince me otherwise....
I'm pretty confident about the distances of 50 & 500 metres (quite useful)
regards ga-ga
Thanks for coming in.....
I'm only just getting to analyse the pics myself -
thought I'd post em first for everybody to muse over........
while I just had dinner....
I think at least one is a red-herring.........
I think Chevron 70 is locked on the fir trees (or one branch) and so not properly focused on the Chevrons.....
see if you can come to logical conclusions without that one.........
my understanding of the 1.5x is 1.5 times the focal length......
thats by firm belief unless anybody wants to convince me otherwise....
I'm pretty confident about the distances of 50 & 500 metres (quite useful)
regards ga-ga
ga-ga
Senior Member
Tom,
sorry, I forgot to say thanks for that -
I had overlooked that possibility and thats just the sort of imput I was looking for!......
regards ga-ga
sorry, I forgot to say thanks for that -
I had overlooked that possibility and thats just the sort of imput I was looking for!......
regards ga-ga
ga-ga
Senior Member
as I said in reply to Ian
I think at least one is a red-herring.........
I think Chevron 70 is locked on the fir trees (or one branch) and so not properly focused on the Chevrons.....
I'll retake that tomorrow - and maybe do a bit of gardening to make sure I can get a focus through the branches......!!
In the mean time......
If we look at the degree of sharpness on the fir tree in the set of 46.8 shots ....
the landscape default is coming back into sharper focus than in the shot focused on the chevrons.... does anybody concur?.......
suggesting that the landscape default is between 50 & 500 metres ......???
this would tie in with the conclusion I'm being drawn to.......
regards ga-ga
I think at least one is a red-herring.........
I think Chevron 70 is locked on the fir trees (or one branch) and so not properly focused on the Chevrons.....
I'll retake that tomorrow - and maybe do a bit of gardening to make sure I can get a focus through the branches......!!
In the mean time......
If we look at the degree of sharpness on the fir tree in the set of 46.8 shots ....
the landscape default is coming back into sharper focus than in the shot focused on the chevrons.... does anybody concur?.......
suggesting that the landscape default is between 50 & 500 metres ......???
this would tie in with the conclusion I'm being drawn to.......
regards ga-ga
We are discussing where Landscape default focus actually comes so
that you can use it for just the shots you've mentioned.
It would be nice if we can prove that infinity but at the moment
I'm not sure.
I've just uploaded two sets of pics focused at 50m,500m and
lanscape default - with and without a 1.5x teleconverter (which
makes the focusing more precise).
http://www.pbase.com/johngregson/infinity
Lets all have a look and make any observations we can see....
regards ga-ga
I am pretty new to photography on a whole. So most of this what
your mentioning is beyond me so maybe if I explain the two kind of
shots you may be able to help.
One would be to go and shoot a seascape shot. Say some rocks some
water. Ideally I would want F11 and max shutter speed of say 10-15
seconds. the next kind of shot would be a moon shot between
tree's. Again if possible would it be best to use F11 and a slow
shutter speed of say 10-15 seconds.
On reading this for infinity I presume I would cover the lense with
my hand and switch on the camera in manual mode. Have the settings
presetup. Press half way down on the manual focus setting and then
remove my hand and then press completley down on the button?
Obvbiously for the moon shot I would want to zoom in as close as
possible and then follow the same procedure.
If I am going wrong here in any of my simple procedures, lease can
you advise if where and how to correct what is wrong. I hope my
questions make sense
Howie
Thanks in advanced.
Well, at f=46.8 / F=2.8 hyperfocal distance is appr. 150 meters, near sharp at appr. 75m, far sharp infinity. Doesn't that explain it all?? I think I'm going ga-ga too......................................
--
Regards,
Tom
(FinePix S602z)
http://www.pbase.com/tomcee
S602Z FAQ:
http://www.marius.org/fuji602faq.php
--
Regards,
Tom
(FinePix S602z)
http://www.pbase.com/tomcee
S602Z FAQ:
http://www.marius.org/fuji602faq.php
Means both. With the converter on, the FL goes from 11.7 to 70.2 mm, still giving 6x range but at 1.5x the former FL and size at each lens position.
Still don't understand why the DOF calculations don't fit, unless the chevrons are really only near sharp. Would help to have a more exact test, I suppose.
ianR
Veteran Member
Oh yes, of course that's the way it works.
I always thought it would be 1.5x magnification anyway but thanks for pointing that out.
regards
Ian
6900
I always thought it would be 1.5x magnification anyway but thanks for pointing that out.
regards
Ian
--
6900
ga-ga
Senior Member
Tom,
I think something like that fits........
if the 70 chevrons was misfocussed....
Dofmaster calculates 110 for the Hyperfocal though........
I'm gonna retake the 70 chevrons tomorrow (weather permiting)
and repost it ......
regards ga-ga
I think something like that fits........
if the 70 chevrons was misfocussed....
Dofmaster calculates 110 for the Hyperfocal though........
I'm gonna retake the 70 chevrons tomorrow (weather permiting)
and repost it ......
regards ga-ga
ga-ga
Senior Member
Sanman!....
I think the 70mm focused on the chevrons was mis-focussed and locked on a branch at about 50m ........ I'm going to try again tomorrow........
regards ga-ga
I think the 70mm focused on the chevrons was mis-focussed and locked on a branch at about 50m ........ I'm going to try again tomorrow........
regards ga-ga
Right, but that's what doesn't fit the DOF calculations. The tree branch and the chevrons shouldn't both be in focus.
ga-ga
Senior Member
Thats a good point !......
even if the branch has grabbed the focus at 50m according to the dof calcs the chevrons at 500 should be way out of focus..............
hmmmmm.....
looks like it needs a much larger coc......???
sorry go to go out today and its really drab anyway - no chance of a retake...
regards ga-ga
even if the branch has grabbed the focus at 50m according to the dof calcs the chevrons at 500 should be way out of focus..............
hmmmmm.....
looks like it needs a much larger coc......???
sorry go to go out today and its really drab anyway - no chance of a retake...
regards ga-ga
ianR
Veteran Member
But it can't have.
35mm is always quoted as 0.030 or 0.025. If you divide that by the same ratio as for the lens (7.8 equalling 35mm) then the CoC must be either 0.0056 or 0.007.
It can't be any bigger unless they are lying about the lens angle.
What about this.
Originally you said the chevrons were about 250mtrs away.
Well if you take a CoC of 0.007 and an F3.1 at 210mm and you can imagine that it actually was sharp focused at somewhere around 75mtrs, then it should be in focus from just under 50mtrs to about 250mtrs.
Is that possible?
Ian
--
6900
ga-ga
Senior Member
Hi Ian ---
this one is very puzzeling....
I actually paced out the distance to the firtree.....
so I'm very confident about the 50 metres.....
I originally guessed at the chevrons as 250 metres...... and revised it to 500 metres after looking at a local map.......
which now makes me pretty confident about the chevrons being 500 metres
I could pace out the distance all the way to the chevrons -
put it seems right having looked at the map......
regards ga-ga
this one is very puzzeling....
I actually paced out the distance to the firtree.....
so I'm very confident about the 50 metres.....
I originally guessed at the chevrons as 250 metres...... and revised it to 500 metres after looking at a local map.......
which now makes me pretty confident about the chevrons being 500 metres
I could pace out the distance all the way to the chevrons -
put it seems right having looked at the map......
regards ga-ga
ianR
Veteran Member
In that case either the CoC is the same as a D-60, or the real focal length of the lens at telephoto is about 32mm or the F no at the telephoto end is really 5.6, or some some of combination of inaccuracy of all three. Huge discrepencies.
There is something very seriously wrong here in any case. I'd really like to know what's going on here.
What I was trying to say is this: is it at all possible that you focused on the tree at 50mtrs but the lens backfocused to about 75mtrs? That could squeeze it just, but otherwise I'm totally stumped. There just has to be one of those factors that's seriously wrong and that's very disturbing.
regards
Ian
6900
There is something very seriously wrong here in any case. I'd really like to know what's going on here.
What I was trying to say is this: is it at all possible that you focused on the tree at 50mtrs but the lens backfocused to about 75mtrs? That could squeeze it just, but otherwise I'm totally stumped. There just has to be one of those factors that's seriously wrong and that's very disturbing.
regards
Ian
--
6900
Ian,
I think I'm getting lost on this one: at f-46.8 and F=2.8 hyperfocal distance is somewhere between 120 and 160 meters (depens how conservative or progressive you count theCOC). Half the hyperfocal distance (say 60meters) to infinity would be sharp. Where my thinking went wrong??
--
Regards,
Tom
(FinePix S602z)
http://www.pbase.com/tomcee
S602Z FAQ:
http://www.marius.org/fuji602faq.php
I think I'm getting lost on this one: at f-46.8 and F=2.8 hyperfocal distance is somewhere between 120 and 160 meters (depens how conservative or progressive you count theCOC). Half the hyperfocal distance (say 60meters) to infinity would be sharp. Where my thinking went wrong??
--
Regards,
Tom
(FinePix S602z)
http://www.pbase.com/tomcee
S602Z FAQ:
http://www.marius.org/fuji602faq.php
ga-ga
Senior Member
ga-ga
Senior Member
Get Dofmaster Tom ......
http://www.dofmaster.com
its free under request of a contribution to a good cause........
regards ga-ga
http://www.dofmaster.com
its free under request of a contribution to a good cause........
regards ga-ga
O.K. I used this one http://poet.tomud.com/pub/hyperfocal.xls
But with DOF Master it gives even more logical figures:
Hyperf.dist 110 meters F=46.8 f=2.8. So default focus at hyperf.dist (110 meters) gives 55 meters to infinity sharp. Am I still missing the point, or just loco??
--
Regards,
Tom
(FinePix S602z)
http://www.pbase.com/tomcee
S602Z FAQ:
http://www.marius.org/fuji602faq.php
But with DOF Master it gives even more logical figures:
Hyperf.dist 110 meters F=46.8 f=2.8. So default focus at hyperf.dist (110 meters) gives 55 meters to infinity sharp. Am I still missing the point, or just loco??
--
Regards,
Tom
(FinePix S602z)
http://www.pbase.com/tomcee
S602Z FAQ:
http://www.marius.org/fuji602faq.php
ianR
Veteran Member
Back focusing is where the lens/camera doesn't really focus at the thing it's pointed at but behind it. Front focusing is the opposite.
There was a camera that had a really bad problem with this as I recall but I don't remember the details.
It's extremely unlikely but I was just suggesting the idea that although you focused at 50m the lens really focused at something well behind that.
It's amazing whatever it is.
Ian
6900
There was a camera that had a really bad problem with this as I recall but I don't remember the details.
It's extremely unlikely but I was just suggesting the idea that although you focused at 50m the lens really focused at something well behind that.
It's amazing whatever it is.
Ian
--
6900
ianR
Veteran Member
Hi Tom
It IS confusing isn't it.
The figures I was using was if the Fno is 3.1 at telephoto and 46.8mm and a CoC of 0.007, then 72mtrs gives a DOF from 42m to 250M, based on the idea that the chevrons were at 250m
But, ga-ga has said that the chevrons are definitely nearer the 500m mark so that's irrelevent now .
Your figures look right so no way can the chevrons be in focus if he was focusing on the tree. Neither with the add-on or not. If the default is to the hyperfocal then yes that would be right. But the default doesn't seem to have as much DOF does it??
To me the one that has the most DOF is MF fir tree. It's true that the others may be affected by lighting conditions but forgetting those, this one should be impossible in any case.
Loved the test shots by the way, superbly devised test with the colour, polystyrene, plastic, fake hair etc.
regards
Ian
6900
It IS confusing isn't it.
The figures I was using was if the Fno is 3.1 at telephoto and 46.8mm and a CoC of 0.007, then 72mtrs gives a DOF from 42m to 250M, based on the idea that the chevrons were at 250m
But, ga-ga has said that the chevrons are definitely nearer the 500m mark so that's irrelevent now .
Your figures look right so no way can the chevrons be in focus if he was focusing on the tree. Neither with the add-on or not. If the default is to the hyperfocal then yes that would be right. But the default doesn't seem to have as much DOF does it??
To me the one that has the most DOF is MF fir tree. It's true that the others may be affected by lighting conditions but forgetting those, this one should be impossible in any case.
Loved the test shots by the way, superbly devised test with the colour, polystyrene, plastic, fake hair etc.
regards
Ian
--
6900
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