self calibration question

KIPAX

KIPAX

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KIPAX Lancashire UK
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Lets say I have a person stood on grass 50 yds away and I take a pic with a 400 lens... f2.8

I can see the line of grass thats in focus is slightly behind the person..

I would set my self calibration to a minus number ..eg -x ...

Correct?

But how much different should 1 notch make..


OK Common sense would say test and see where the line moves... but canon being canon and canon saying themselves that not all focus will be the same every time.. I just wanted some idea before I start testing.. believe me its not as simple as take shot.. view.. take next ..until right.. not at all.. should be but isnt :(

anyone know given the aprox distance what -1/2/3/ etc would do.. hardly noticable move of the grass or?
 
It's easy when you've done it a few times Tony, but I spent hours at first and nearly went blind. I have to do it a lot for work now, testing lenses.

I'm getting a Canon 400L 2.8 MkII in a couple of weeks so we'll see how I get on, though I won't be doing it at 50m. There's too much DoF at that range to see things clearly enough. If a lens like that is not spot on over at least 10m to infinity, I'd send it back to Canon with a snotty note.

Anyway, for that situation I would move forward to about 20m and just put a large box on the grass, square to camera, making sure the AF point cannot lock on to anything else. See how the focus shifts over the grass.

You want minus comp to pull the AF plane closer. How much shift you get with each increment varies with lens. AF works by changes in depth of focus (not field). My experience is when you get down to +/-2 or so increments, you are very close to optimum and changes can be hard to see unless you're close. Possibly too close for the work you do.

Another way with long lenses is to stick a magazine page on to a wall. The brickwork helps to line things up square. Solid tripod, IS off, then shoot at increments of 5, then narrow that down to 2-3, then try and nail it absolutely, and finally shoot a sequence at your optimum setting, defocusing each time, to check consistency. That works well, but of course you don't have the benefit of being able to see how the focus moves with adjustment - you just know when it's right. Compare to live view AF as double-check.

If you can light the target with a flash gun on lowish power to absolutely freeze movement, so much the better. You should then run through a final-final check hand-held or monopod with IS on.
 
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KIPAX said:
Lets say I have a person stood on grass 50 yds away and I take a pic with a 400 lens... f2.8

I can see the line of grass thats in focus is slightly behind the person..

I would set my self calibration to a minus number ..eg -x ...

Correct?

But how much different should 1 notch make..


OK Common sense would say test and see where the line moves... but canon being canon and canon saying themselves that not all focus will be the same every time.. I just wanted some idea before I start testing.. believe me its not as simple as take shot.. view.. take next ..until right.. not at all.. should be but isnt :(

anyone know given the aprox distance what -1/2/3/ etc would do.. hardly noticable move of the grass or?
Click to expand...


Why not lay cones/shoes/beer cans/womens knickers etc out on the grass to see which way to bring or push your adjustment.

Canon recommend 50 x focal length so you would ideally be at 20m to test the lens.

Have you looked at Focal?

http://www.reikan.co.uk/focal/

And a discount page from this link only...

http://www.reikan.co.uk/focal/mbp45/
 
Cheers.. I ahve never had any luck wiht things like magazines or setups as the focus always moves.. not just talking about a 400.. but any lens I ever tried before.. I can never get the same result 2 or 3 times in a row...

I ahvent got a tripod..just use a monopod


so 20meters.... about 21 yds in old money :)

will try the box... would be great if it gave the same result every time.. would be easy to move change settinjgs and get right

i got this lens brand new and at f4 is pure perfect.. but suddenly had a lot of trouble this weekend and loking at the pics they are all out slightly.. subjects at half way line (around 50+yds) even at f4 i can see in focus grass just behind... only ever used f2.8 in low light with high iso so you dont notice a slight miss calibration as your pics need a certain amount of work anyway.... hard to explain..


calibrating a lens like this is by far the worse ever part of photogrpahy :(
 
KIPAX said:
Cheers.. I ahve never had any luck wiht things like magazines or setups as the focus always moves.. not just talking about a 400.. but any lens I ever tried before.. I can never get the same result 2 or 3 times in a row...

I ahvent got a tripod..just use a monopod


so 20meters.... about 21 yds in old money :)

will try the box... would be great if it gave the same result every time.. would be easy to move change settinjgs and get right

i got this lens brand new and at f4 is pure perfect.. but suddenly had a lot of trouble this weekend and loking at the pics they are all out slightly.. subjects at half way line (around 50+yds) even at f4 i can see in focus grass just behind... only ever used f2.8 in low light with high iso so you dont notice a slight miss calibration as your pics need a certain amount of work anyway.... hard to explain..


calibrating a lens like this is by far the worse ever part of photogrpahy :(
Click to expand...

Can be a frustrating business. I now find it easy (made my own large version of a Spyder LensCal, v easy with a bit of foam board) but there is certainly nothing worse than inconsistent AF. You never know if it's you or the lens.

I know you use your kit a lot Tony so maybe it's a bit worn inside. Or maybe the camera has taken a knock, but you should certainly get a very good idea of what's what using the box and grass for reference. Monopod should be fine. Keep the pics and notes if you need to send to Canon.

PsiFox said:
Interesting Link. Have you used the software?
Click to expand...

There's a long thread about this software elsewhere on here. I'm not convinced by it TBH. It's not proved 100% reliable and you still need a good target and set-up and that is the only bit that takes a bit of time. I bet everyone that has used it has also double-checked by doing it manually, so what's the point ;)
 
HoppyUK said:
There's a long thread about this software elsewhere on here. I'm not convinced by it TBH. It's not proved 100% reliable and you still need a good target and set-up and that is the only bit that takes a bit of time. I bet everyone that has used it has also double-checked by doing it manually, so what's the point ;)
Click to expand...
That's a bit rich coming from a pro tester. What if all your readers do the same thing after you have given results from some of your lighting tests? You may be out of a job.

Just saying.
 
Brick walls are good although you may need to find a long wall!

Taken this afternoon with the 100-400 I bought in the classifieds

testyni.jpg
 
One unit of MA is equal to 1/8th of the single sided depth of focus. If you know your subject distance then a DoF calculator will give you an idea of the DoF each side of your subject and you should get a reasonable assessment of where you're heading.....in parctice, it might be different.
Note...depth of focus is not the same as depth of field but the approximation should be a least as good as your guesstimate of where focus actually lay.

Bob
 
tiler65 said:
That's a bit rich coming from a pro tester. What if all your readers do the same thing after you have given results from some of your lighting tests? You may be out of a job.

Just saying.
Click to expand...

:thinking: You've lost me there.

admirable said:
Brick walls are good although you may need to find a long wall!

Taken this afternoon with the 100-400 I bought in the classifieds

testyni.jpg
Click to expand...

That isn't what I meant by a using a brick wall, though it's a perfectly good test. It's basically the same as the box sitting on the grass mentioned above, with an excellent view of what's happening fore and aft.

Just that the target needs to be big enough to absolutely ensure the AF doesn't pick up on anything at a different distance and that looks like it's at relatively close range, and not the 20-50m Kipax is wanting to check it at.
 
HoppyUK said:
:thinking: You've lost me there.
Click to expand...

The point being that 'I bet everyone that has used it has also double-checked by doing it manually, so what's the point' is saying why bother with any testing reviews.
 
HoppyUK said:
That isn't what I meant by a using a brick wall, though it's a perfectly good test. It's basically the same as the box sitting on the grass mentioned above, with an excellent view of what's happening fore and aft.

Just that the target needs to be big enough to absolutely ensure the AF doesn't pick up on anything at a different distance and that looks like it's at relatively close range, and not the 20-50m Kipax is wanting to check it at.
Click to expand...

It is at close range (15ft) and taken at 400mm the same as Kipax, there's no reason why it couldn't be done at 20m. Surely at 20m you have to zoom in to see sharpness? I've also done the test that's square on to a newspaper or cereal packet but I prefer this.
 
HoppyUK said:
Just that the target needs to be big enough to absolutely ensure the AF doesn't pick up on anything at a different distance and that looks like it's at relatively close range, and not the 20-50m Kipax is wanting to check it at.
Click to expand...

I think in the past the size of target has been a problem.. I did so much testing with smaller lens using box and ruler before i realised the white ruler wasnt helping..

I have tommorow morning free so am going to have a good test and see what I can find out..looking at 20 yards and somehting big enough on some grass..

It would be easier to send off to canon but would cost a fortune and i havent got the time either.. this is my first day not using it in i dont know how long.... currently busiest time of yr..until end of month i think :)
 
tiler65 said:
The point being that 'I bet everyone that has used it has also double-checked by doing it manually, so what's the point' is saying why bother with any testing reviews.
Click to expand...

Not at all. The Reikan software has been proven to be unreliable with some camera/lens combos by far too many of the beta testers for it to be trusted IMHO. I don't follow your reasoning; it's not the tester that's at fault, but the procedure.

admirable said:
It is at close range (15ft) and taken at 400mm the same as Kipax, there's no reason why it couldn't be done at 20m. Surely at 20m you have to zoom in to see sharpness? I've also done the test that's square on to a newspaper or cereal packet but I prefer this.
Click to expand...

Well yes, that's my point. For the test to work at greater range you would need a much larger target than the water tap to ensure a reliable AF lock-on. And you most certainly would have to zoom in to view the result with any degree of accuracy, even at f/2.8, and view damn carefully!

That's the problem with a lot of AF adjustment tests. Depth of field is often generous at normal shooting distances and the tempation to move close, to reduce DoF and see the changes more clearly, is one of the (many) things that can throw it out. Though by far the most common probelm is user-error.

The optimum AF setting is often a bit of a compromise between close and distant accuracy, so if you get it perfect at very close range there's adanger you will throw it out at more normal shooting distances. Zooms can vary across the focal length range too.
 
HoppyUK said:
It's not proved 100% reliable and you still need a good target and set-up and that is the only bit that takes a bit of time.
Click to expand...

It depends on how many cameras and lenses you have. Setting up the target takes very little time. It's the process of {[defocus - shoot - defocus - shoot - defocus - shoot - change MA setting] - repeat at various MA settings} followed by checking each of those images for the sharpest. That's what takes a huge amount of time.

With Focal you set everything up and start the software. After about two minutes it's finished. So you swap lenses, move the target, start the software and wait another two minutes. I did a dozen different lenses in less time than it took for me to do one lens manually.


HoppyUK said:
I bet everyone that has used it has also double-checked by doing it manually, so what's the point ;)
Click to expand...

I double-checked it by comparing the values to the three that I'd done previously. Very little effort. The point is, it was so easy that I did all of my lenses, not just three (well, one lens with 1.4x and 2x TCs).
 
Tony, I have a spare tripod if you want to borrow one.
 
hollis_f said:
It depends on how many cameras and lenses you have. Setting up the target takes very little time. It's the process of {[defocus - shoot - defocus - shoot - defocus - shoot - change MA setting] - repeat at various MA settings} followed by checking each of those images for the sharpest. That's what takes a huge amount of time.

With Focal you set everything up and start the software. After about two minutes it's finished. So you swap lenses, move the target, start the software and wait another two minutes. I did a dozen different lenses in less time than it took for me to do one lens manually.




I double-checked it by comparing the values to the three that I'd done previously. Very little effort. The point is, it was so easy that I did all of my lenses, not just three (well, one lens with 1.4x and 2x TCs).
Click to expand...

It's a great idea, so long as it's reliable, but right now I don't have that confidence. Given what we know about significant failures with some camera/lens combos so far, how do you know the dozen different lenses you've adjusted are right?

Anyway, I don't plan to be using it any time soon. I really don't mind spending a few minutes, and that's all it is, doing it properly/manually. Get it right, and it's set for good.
 
KIPAX said:
I think in the past the size of target has been a problem.. I did so much testing with smaller lens using box and ruler before i realised the white ruler wasnt helping..

I have tommorow morning free so am going to have a good test and see what I can find out..looking at 20 yards and somehting big enough on some grass..

It would be easier to send off to canon but would cost a fortune and i havent got the time either.. this is my first day not using it in i dont know how long.... currently busiest time of yr..until end of month i think :)
Click to expand...

Tony
Its a pitty you dont live closer to me you could have borrowed mine and do a comparison test between two to see how far out (if it is ) assuming that mine is ok not that i have noticed anything wrong with it :)
 
HoppyUK said:
It's a great idea, so long as it's reliable, but right now I don't have that confidence. Given what we know about significant failures with some camera/lens combos so far, how do you know the dozen different lenses you've adjusted are right?
Click to expand...

Richard,

I don't think anyone is saying that Reikan gives the wrong result it's simply that it fails to get a result with some combinations. There will always be people whose methodology isn't up to scratch and then blame the tools....skewing the reported failure rate in the process.

I have run the software on three 1srs bodies and in excess of ten lenses and achieved good and consistent results with the beta and released versions.
I have one lens (EF50/1.2L) that tests perfectly on both 1D MkIV's and prompts an inconsistency report each time I test in on the 1Ds MkIII. My procedure is sound based on all other lenses running through the setup fine and it is only one body/len combination that fails. Failure does not give the wrong result, it gives a message advising that any result is not to be viewed as good.

I think criticism needs to be based on good evidence and maybe personal experience rather than spurious reports....that wasn't meant to sound harsh...sorry.

Bob
 
Canon Bob said:
Richard,

I don't think anyone is saying that Reikan gives the wrong result it's simply that it fails to get a result with some combinations. There will always be people whose methodology isn't up to scratch and then blame the tools....skewing the reported failure rate in the process.

I have run the software on three 1srs bodies and in excess of ten lenses and achieved good and consistent results with the beta and released versions.
I have one lens (EF50/1.2L) that tests perfectly on both 1D MkIV's and prompts an inconsistency report each time I test in on the 1Ds MkIII. My procedure is sound based on all other lenses running through the setup fine and it is only one body/len combination that fails. Failure does not give the wrong result, it gives a message advising that any result is not to be viewed as good.

I think criticism needs to be based on good evidence and maybe personal experience rather than spurious reports....that wasn't meant to sound harsh...sorry.

Bob
Click to expand...

Not harsh Bob, I haven't used it as you've guessed. I was going to give it a bash, but since there seemed to be plenty of other respected folks doing that, like you and Tim D for example, that was good enough for me :) I accept what you say, but until it is proven to work 100% with everything, there is always potential for doubt.

For example, I have the brand new Tamron 24-70mm 2.8 VC lens here now for a magazine review. It's got new AF, new IS, new everything. Quite possibly it's never been run through the Reikan software by anyone yet, so should I have a go, find that the AF is all over the place, and publish those findings, knowing that this software is new and not totally bug-free?

Or do I spend half an hour doing it manually, and then know for sure what it can do? It's excellent BTW, dead accurate at zero and very consistent. If anything, a smidge more consistent than my Canon 24-105L though we're talking mms over about 3m distance, barely detectable even at 100%.

I guess, my cynicism aside, I just don't see the point of the Reikan method. Bit of a gimmicky toy ;)
 
Well it was all over the place ..I could get a good shot at +10 and one at -10 and inbetween.. also bad pics...

The worse thing was when the sun out... I cant get a single pic in focus in bright sun but I can when overcast.. but again dodgy..

I HAve 2 mkIVs but the 400 has never been on the other one (So the test i did on that didnt mean much accept it was still dodgy) ... so i used the mkiv usualy on the 400 onto the 70-200 which I know is spot on and every shot perfect... so its not the camera..

i am well upset.. gonna send it off to canon first thing monday and hope it dont cost a fortune.. i got this brand new but its over a yr ago.. i think lens warranty is only a yr.. cant rremember.. gotta look it up.
 
I know you've been 'darn sarf' now with your 400 but I recommend Focal. n.b. no connection with the company.

I've found it pretty darn good with my longer lenses with/without TCs.
 
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