[charleychen]

Hi,

I just purchased a marumi super dhg circular polarizer and decided to take some test shots today. All of my images came out less sharp than without the CPL. Is this expected? Or am I doing something wrong?

Thanks.

---

Last edited by charleychen; 05-01-2011 at 08:13 PM.

[alohadave]

Can you post examples of with and without?

It's certainly possible that the filter is causing problems.

[DogLover]

Hi,

I just purchased a marumi super dhg circular polarizer and decided to take some test shots today. All of my images came our less sharp than without the CPL. Is this expected? Or am I doing something wrong?

Thanks.

I have that exact same filter and get great results with it. There's definitely nothing inherently wrong with that filter. Is it possible to get a bad copy of a filter?

[Ratmagiclady]

What focal length of lens, too? I believe some can have problems with extreme wide angles. It's also possible the polarizer's cooked. Does it look sharp enough when you look through it?

[DaveHolmes]

It's also possible the polarizer's cooked

As in warped?

[Jonathan Mac]

Anything you place in the light path will affect the image. Filters will almost always make images softer, dependent on the quality of the filter.

[bdery]

Anything you place in the light path will affect the image. Filters will almost always make images softer, dependent on the quality of the filter.

Indeed. A good quality filter will have no visible effect, but any filter WILL degrade your image.

[newarts]

Indeed. A good quality filter will have no visible effect, but any filter WILL degrade your image.

True and as you point out the degree of degradation matters a lot. It is certainly possible to have degradation that is non-detectable for practical purposes.

The light loss of at least one stop due to the filter resulted in at least twice the exposure time or a one stop larger larger aperture - the first would increase the probability of motion smear and the second might result is a fuzzy image due to a lower f-stop - either of which could be the reason for a softer image.

I suggest doing a good test - like put the camera on a tripod & shoot a photo of something with a crisp edge: shoot with 2 sec delay with and without the filter at the same f-stop. It'll be helpful if the edge is tilted with respect to the optic axis a bit so at least one point on it will be in focus - critically compare the best focus with and without the filter.

I'd like to hear the results.of such a test.

[SOldBear]

If you have a good filter (and Marumi is a good brand), the loss of sharpness may be negligible.

But with a polarizer, you also lose contrast, and that can be perceived as you lose sharpness too.

The sum of two effects make things appear worse than they actually are.

[charleychen]

I did not do any structured testing. I'll try to follow a bit more rigor and post my findings.

[newarts]

I did not do any structured testing. I'll try to follow a bit more rigor and post my findings.

Great! Thanks... whatever your findings they will be of benefit to the group.

[bdery]

I suggest doing a good test - like put the camera on a tripod & shoot a photo of something with a crisp edge: shoot with 2 sec delay with and without the filter at the same f-stop. It'll be helpful if the edge is tilted with respect to the optic axis a bit so at least one point on it will be in focus - critically compare the best focus with and without the filter.

I'd like to hear the results.of such a test.

I do that with all my filters before deciding to trust them or not.

The ones I keep are the ones where I cannot see a difference.

[Ratmagiclady]

As in warped?

Well, sometimes the foil between the layers of glass can be degraded, a bit of delamination in there, etc: I say 'cooked' cause of how I discovered this phenomenon, ...by absentmindedly leaving a polarizer out in the hot sun for, *koff,* Well, Maybe a day and a half.