Macro photography and circular polarizing filter

[rtbaum]

I am new to this community, this being my first post. I have added a 90 mm macro lense to my kit and am curious about the potential benefits of using a circular polarizing filter for macro photos. Any suggestions?

[rpcrowe]

IMO, the only time a CPL might be beneficial in a macro shot is if reflections were a problem. OTOH, you lose two stops or so with a CPL and those extra two stops would probably be handy in macro work since DOF is always razor thin...

[Glenn NK]

I use a CPL with my macro lens on occasion to remove reflections which can blow out or overexpose. To a large extent, a polarizer will remove reflections from non-metallic objects such as plants - so it can be useful.

Quite often, the part of the image that will blow out will be some out of focus leaf in the background that has a strong reflection - very annoying and difficult to deal with once the image is taken.

Another solution is a diffuser that softens direct sunlight thereby lessening the impact of reflections, but at times the diffuser won't be large enough to cover the flower of interest and the entire background and there will be a nasty reflection showing up in the image.

The drawback of the CPL is that it is highly directional, and the flower I'm shooting may be at such an angle to the sun that the CPL is of little or no use.

Perhaps it comes down to this: If one takes a high percentage of closeup floral or macro images, both tools will be of benefit, whether used singly or in combination. If one takes the occasional floral image and can live with reflections, the cost may not be worthwhile.

There is a third option that I learned of many years ago from the magazine Pop Photo: Shoot flowers in the rain, or on a cloudy day. Cloud cover acts somewhat like a polarizer removing many reflections. When reflections are largely removed, colour saturation increases markedly (which of course applies to the use of diffuser and polarizer). Another advantage of rain is that raindrops on a flower can add to interest to the image. Worried about rain? I used my non-sealed 30D many hours in light drizzle and showers simply by draping a terry towel over the camera; I now have a purpose made rain coat made by Kata (model E-72).

Reflections will be inevitable, and in fact are desirable to provide some modeling and interest. And if light didn't reflect, we'd have no photography and no vision.

Glenn

PS. Richard's comment about the loss in f/stop from a polarizer is valid, however, I rarely if ever shoot flowers without a tripod. And if one is focus stacking (to achieve greater dof), then shooting without a tripod is IMO, madness.

[Photon Hacker]

There is a third option that I learned of many years ago from the magazine Pop Photo: Shoot flowers in the rain, or on a cloudy day. Cloud cover acts somewhat like a polarizer removing many reflections.

If you mean clouds polarize light (Not just diffuse it), could you please explain the physics of that phenomenon?.

[Glenn NK]

If you mean clouds polarize light (Not just diffuse it), could you please explain the physics of that phenomenon?.

Clouds diffuse the light, making it less directional and softer, thereby reducing reflections. Reducing reflections will improve colour saturation. A CPL obviously uses a different method entirely, but the result is reduced reflections and improved saturation of colour.

Sorry about the misleading comment.

Glenn

[Geoff F]

I have tried a polariser for insect shots, Randy, but found it actually made the problems worse.

It just darkened the scene which caused more flash to be used. And without flash I just got an excessively dark overall scene.

Using flash output compensation to reduce the power seems to work best for me. Or try to avoid direct sunlight. But even then I still sometimes get some 'hot spots' from those shiny insects.

[John C]

I have found that a CPL filter is sometimes useful for maintaining color accuracy for flowers that are in full sun, especially for blues and reds. You can't always wait for an overcast day and some flowers really need full sun to open fully.

For other macro shots, such as insects as mentioned above or less intensely lit subjects in general, the CPL just tends to remove light so that you need to adjust the exposure accordingly (it doesn't help in these cases.).

[rtbaum]

I appreciate the advice from all of you. I recently purchased a used Tamron 90 mm macro and have been lurking in various photo sites, C in C has been one the more informative in my opinion. I have more questions about technique that will post in the future. Currently, I am working at proper focus and depth of field; Kind of enjoying revisiting days of yore when there was no such thing as AF.

[Glenn NK]

One of my favourite tools for flower photography in the sun:

http://www.digitaljuice.com/products...FaQbQgod104aoQ

Scroll about 2/3 down the page to where it shows the five modes. Four of the modes are as a reflector, while removing the reflective cover reveals the diffuser core. While I use the diffuser mode most often to reduce the harshness of sunlight, I often use the one of the reflector sides to illuminate the dark side of a flower.

Glenn

[Hero]

Did you btw know that the colouring on the shields of some insect (namely beetles) is there due to polarisation? You pretty much kill that pretty neat trick when using a polarisation filter.

[revi]

Did you btw know that the colouring on the shields of some insect (namely beetles) is there due to polarisation? You pretty much kill that pretty neat trick when using a polarisation filter.

Are you sure it's the polarisation that causes the colour? I was always taught that some of the metallic greens and blues were due to iridescence, or interference between incoming and reflected light (see here for instance ).

(the reflection can also partly polarise the light, so using a polariser would lose part of the colours, but still...)

[Hero]

Are you sure it's the polarisation that causes the colour? I was always taught that some of the metallic greens and blues were due to iridescence, or interference between incoming and reflected light (see here for instance ).

(the reflection can also partly polarise the light, so using a polariser would lose part of the colours, but still...)

Could well be, just know that using polarisers around beetles makes them dull black, and since the colour changes with the angle you look at it I just assumed it was due to polarisation.