How do you test a lens vignetting?

How do you test a lens vignetting?

You can test lenses for vignetting by shooting images of a perfectly evenly illuminated white or grey card. Getting even illumination isn’t always as simple as it sounds since this is a pretty sensitive test. Sunlight is a good light source.

How do you tell if your lens is a bad copy?

How sharp is the subject in all four photos? If it looks about the same in each corner, your lens is very likely a good copy. If one or more corners is clearly less sharp than the others, repeat this test. If your results continue to show a lack of sharpness in the same corner(s), your lens is very likely decentered.

How can you tell if a lens is sharp?

And the solution is… first test your lens for sharpness, as there’s a high possibility that your lens is soft. Most lenses are not very sharp at their widest aperture. Instead, they are sharp when stopped down by 1 stop or sometimes 2 stops.

Is my lens decentered?

When testing zooms for decentering you should do it at the extremes and in the middle. If your lens has field curvature the corners will look worse than the center. To check centering you need to compare the corners to each other, not compare the corners to the center.

How often should a lens be calibrated?

You need to calibrate only if and when you notice that your camera’s autofocus isn’t producing a clear photo with a certain lens. It can depend on how much wear your equipment gets. But for some, this may occur about every six months to two years for each camera and lens combination.

What should I check before buying a lens?

Check the lens for fungus, scratches and dust. The best way to do that is to shine some light through the lens (with a simple flashlight – even the LED light from your smartphone should suffice) – any imperfections should then be clearly visible.

What is lens testing?

Lens testing is seen as a way to “make sure you got a good one”. This is a fairly recent phenomenon which correlates well with the rise of digital SLRs. The reason for this is probably that users can now take a shot and examine it in exquisite (or perhaps excruciating) detail a few seconds later.

What do the numbers on the lens testing chart mean?

The images you shoot can be analyzed for sharpness and chromatic aberration quite easily. The numbers on the lens testing chart represent the line pairs per mm (lp/mm) values of the test patterns they are next to. These patterns should be pretty accurate down to the set marked 5.0.

What are the resolution patterns for the lens testing?

The lens testing resolution patterns are based on those used for the NBS 1010A test chart. There’s a high contrast set on the left of center and a low contrast set on the right of center. In the center is a checkerboard pattern which is used for focusing.

What size target should I use for lens testing?

If you were doing lens testing using a full frame DSLR, you’d put the targets at the center and corners of a 24″ x 36″ rectangle to get the same magnification ratio. The target itself is shown below: You can download a high resolution printable version of this image (as a Zipped JPEG) via THIS LINK .