Any tips on shooting @ 45 degrees for focus test

shoshone

shoshone

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Jamie
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My tripod head doesn't have any degree marks (ball head).

I understand it is crucial to take test shots at 45 degrees. I have tried creating a diagonal from a square but I'm not convinced I've really got it right?
:thinking:
 
Get the camera level using a spirit level and then have the piece of paper at 45deg...
 
pxl8 said:
Get the camera level using a spirit level and then have the piece of paper at 45deg...
Click to expand...


Thanks for that. I have a spirit level on the tripod, but a ball head? I'm just being thick arn't I. Ah I should get a hot shoe spirit level shouldn't I!
:amstupid:

Jamie
 
The tripod normally has markings for getting the head level so as long as the bubble also says level you should be ok - you don't need to be perfectly accurate for a focus test. The 45 deg angle is more so you can easily tell if you're front or back focused than you'd be able to do if you had the paper at 90deg.
 
pxl8 said:
The tripod normally has markings for getting the head level so as long as the bubble also says level you should be ok - you don't need to be perfectly accurate for a focus test. The 45 deg angle is more so you can easily tell if you're front or back focused than you'd be able to do if you had the paper at 90deg.
Click to expand...

The last time I did this I was pretty sure my 24-70 was back focussing, however it varied so much through the zoom range and apertures. I'm trying again so that I can set the microadjustment on the new body.

Has anyone tried this focus test as an alternative ??

http://www.openphotographyforums.com/forums/showthread.php?t=4708

Jamie
 
The problem with a test like that is you don't get any information about front or back focusing, only right or wrong. The 45deg test is much better, esp. if you're going to tweak the AF micro adjust.

I've set up the adjustments on my 1DIII but did it in a "real world" setting by hand holding and taking shots, checking, rinse, repeat. I felt this way the results would be better than an in a clinical testing environment.
 
pxl8 said:
The problem with a test like that is you don't get any information about front or back focusing, only right or wrong. The 45deg test is much better, esp. if you're going to tweak the AF micro adjust.

I've set up the adjustments on my 1DIII but did it in a "real world" setting by hand holding and taking shots, checking, rinse, repeat. I felt this way the results would be better than an in a clinical testing environment.
Click to expand...

pxl8, many thanks for that observation. I'll try real life like you, any reason for not using a tripod?

Jamie
 
Just because I rarely use a tripod and when I do I'm probably shooting tethered anyway so focus is manual. I felt it was better to get the best results from the mircoadjust for how I normally hold and shoot the camera. I did end up with some adjustments on all my lenses and I do notice slightly sharper results so I must have done something right :lol:
 
pxl8 said:
Just because I rarely use a tripod and when I do I'm probably shooting tethered anyway so focus is manual. I felt it was better to get the best results from the mircoadjust for how I normally hold and shoot the camera. I did end up with some adjustments on all my lenses and I do notice slightly sharper results so I must have done something right :lol:
Click to expand...

OK many thanks
Jamie
 
You should be doing focus tests on a flat object at 90 degrees from the lens not on one at 45 degrees, it needs to be high contrast ie black and white to give the focus point something to lock onto, your scale for determining if its focused correctly should be angled at 45 degrees with the 0 point level with the centre of the flat target.

See the info below (This info/photos is from POTN and belongs to them, its here just for reference)

To make sure there is no user error in question this problem must be verified with testing, and the test should be done (according to Canon Japan):

- from 2.5m
- with a 50mm lens
- in at least 12EV light (ISO 100, 5.6 1/125 equiv.)
- on sturdy tripod (mirror lock and external/timed release)
- "One shot" focus mode
- manual focus point (center).
- Largest aperture of the lens. This means use smallest f-number you can get.

The testing target can be built from a paper with some scale, and a cardboard focus point with white rectangle of black background. Canon test setup is something like this:

test.gif


The drawing is not in scale, sorry). The focus rectangle should be tack sharp and on the scale you can see how depth-of-field distributes. If rectangle is out of focus the scale tells you how much it is out and into what direction.

Image of this test (from Canon's Finnish repair centre), with 200mm lens:

focus.jpg


Other usable test is at http://www.hkdotcom.net/Francis Ph...Test/index.htm - you can use that chart in above Canon type testing, but you don't want to focus to the chart itself as told on that page. It is important that what you focus to is a flat plane facing to the camera - any 3D information there makes test results unreliable.

Make sure that viewfinder focus rectangle sees only one possible focus point. Always use One Shot focus mode with centre point only for testing. Alighn the test so that the plane of focus is not slanted - if you think you can't do the test ask someone more experienced to do it for you.

FACT:
Do not to fully trust you own tests - they just indicate something. If you get repeatedly off focus results, take the camera to repair and let them test it again there and make their own conclusions. In the end Canon is the only authority that can confirm any focus errors in your camera body.

FACT:
Focus error can be "front" focus or "back" focus. Front means camera focuses closer to you, back means the camera focuses further away from intended focus point.

FACT:
Slight focus shifting (repeated tries give slightly different focus lock) is normal to autofocus systems. Focus shifting may be increased by dust and dirt inside camera body parts, dust or dirt on lens back, dust or dirt on filters/lens.

FACT:
Focusing can get out of calibration if you drop your camera or handle it rough.

FACT:
Resetting camera does not fix focusing.

FACT:
I may have forgotten some facts.
 
FACT:
Canon Digital Photography Forums don't allow image hotlinking ;-)
 
mho said:
You should be doing focus tests on a flat object at 90 degrees from the lens not on one at 45 degrees, it needs to be high contrast ie black and white to give the focus point something to lock onto, your scale for determining if its focused correctly should be angled at 45 degrees with the 0 point level with the centre of the flat target.

See the info below (This info/photos is from POTN and belongs to them, its here just for reference)

To make sure there is no user error in question this problem must be verified with testing, and the test should be done (according to Canon Japan):

- from 2.5m
- with a 50mm lens
- in at least 12EV light (ISO 100, 5.6 1/125 equiv.)
- on sturdy tripod (mirror lock and external/timed release)
- "One shot" focus mode
- manual focus point (center).
- Largest aperture of the lens. This means use smallest f-number you can get.

The testing target can be built from a paper with some scale, and a cardboard focus point with white rectangle of black background. Canon test setup is something like this:

test.gif


The drawing is not in scale, sorry). The focus rectangle should be tack sharp and on the scale you can see how depth-of-field distributes. If rectangle is out of focus the scale tells you how much it is out and into what direction.

Image of this test (from Canon's Finnish repair centre), with 200mm lens:

focus.jpg


Other usable test is at http://www.hkdotcom.net/Francis Ph...Test/index.htm - you can use that chart in above Canon type testing, but you don't want to focus to the chart itself as told on that page. It is important that what you focus to is a flat plane facing to the camera - any 3D information there makes test results unreliable.

Make sure that viewfinder focus rectangle sees only one possible focus point. Always use One Shot focus mode with centre point only for testing. Alighn the test so that the plane of focus is not slanted - if you think you can't do the test ask someone more experienced to do it for you.

FACT:
Do not to fully trust you own tests - they just indicate something. If you get repeatedly off focus results, take the camera to repair and let them test it again there and make their own conclusions. In the end Canon is the only authority that can confirm any focus errors in your camera body.

FACT:
Focus error can be "front" focus or "back" focus. Front means camera focuses closer to you, back means the camera focuses further away from intended focus point.

FACT:
Slight focus shifting (repeated tries give slightly different focus lock) is normal to autofocus systems. Focus shifting may be increased by dust and dirt inside camera body parts, dust or dirt on lens back, dust or dirt on filters/lens.

FACT:
Focusing can get out of calibration if you drop your camera or handle it rough.

FACT:
Resetting camera does not fix focusing.

FACT:
I may have forgotten some facts.
Click to expand...


FACT:

I'm going to have to read this several times over, because this time left me high and dry....when I got to the bit about not 45 degrees..and then 'your scale for determining if its focused correctly should be angled at 45 degrees with the 0 point level with the centre of the flat target'...I must have flipped.

Forgive me for being so obtuse....I'll read this over again until I understand what you just said.
 
I think it's suggesting you focus on something that's flat on to the camera but also have a 45deg slope to check the front/back focusing situation if the focus is out. The reason being, and a sensible one, is that focusing on an angle is likely to be unpredictable.

So you want something like this (seen from the side)

Code: 
\|
 |\

The verticals are the focus target, the angles are some kind of scale showing front/back focusing errors.
 
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