Focus test

[Paul Verrips]

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If i want to test my M9 with my lenses for correct focus, wich focuschart do i need to use? Any type or a specific type?

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[Paul Verrips]

If i use the LCD screen to check infocus on my M9(upgraded-P), how far can i zoom before it's behind judgement? There are 4 zoom steps.

[lars_bergquist]

If i want to test my M9 with my lenses for correct focus, wich focuschart do i need to use? Any type or a specific type?

 

For close focus: The classical staggered matchboxes, or playing cards, or anything else with moderately fine print on it. Distant focus: a picket fence, or a row of light poles, receding into the distance – and remember which post or pole you focused on!

 

If i use the LCD screen to check infocus on my M9(upgraded-P), how far can i zoom before it's behind judgement? There are 4 zoom steps.

 

If you use the screen for a quick check, you can go three steps, in my experience. But take the trouble to take the pictures into your computer, at least, for more precise viewing.

 

The old man from the Age of Scale Focusing

[adli]

I found the best solution for close focusing to be:

1. Put a tiny object (3-4 mm) on a surface with fine texture.
   
2. Focus on the tiny object, camera approximately 30 degrees above surface, on a tripod
   
3. The texture on the surface will easy show a stripe across the picture which is in focus
   

[wattsy]

I agree with Lars that the best test for near focus is the 'staggered matchbox' test rather than the ruler at an angle test that is often recommended. The staggered object approach tends to eliminate parallax errors and it more closely resembles real world use. You can see straight away if you have front or back focus problems.

 

Another quick and dirty technique I sometimes use if I have doubts about a lens or camera is to focus on an object (at any distance) as I would in normal use and take a shot. I then take another couple of shots after manually tweaking the focus of the lens a tiny amount in both directions. You can then zoom in on the rear LCD and directly compare the three shots (if you keep holding the 'set' button whilst using the left and right buttons, the image stays at the same zoom level for each shot). Even allowing for the crappy quality of the preview you can easily get a feel for which of the three shots looks in best focus. Of course, this test doesn't necessarily prove a problem with the camera or lens – it might just be that the user needs glasses or has inconsistent technique – but it is a good indicator that you might not be achieving ideal focus (for whatever reason) in real world conditions.

[erl]

A standardized procedure is important, otherwise you risk differing results each time you test. Below is a summary of the method I have adopted.

 

I set up a 1 mtr rule with a black line I have marked on it, and position it on a picket fence line. I then set the camera ona tripod and shoot oblique pics at 1, 2, 5, 10, 20mtrs. Each range is exposed at varied apertures starting at max for the lens and progressively closing down at least 4 stops. Longer ranges are focused on the tall picket with the ball on top as the black line can not be 'seen' at long ranges.

 

See two sample pics below.

Close range target.

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Longer range target

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M9 + 75mm Cron used for these examples.