Reflection

[jin]

I was shooting butterfly egg with flash through objective but can't seem to get rid of the reflection from the surface even with many diffuser, reduce flash power.

However I was able to get rid of reflection by using continue LED light source but I 'need' to shoot using flash for sharper image due to vibration in the system.



Kindly advice :-)

P/s: what are those white things inside the egg?

[Harold Gough]

You could use a polariser in front of the flash and another, rotated to minimise reflections, on the lens. Of couse, that will significantly reduce the intensity of the light reaching the lens.

Harold

[rjlittlefield]

Search on "cross polarization". There are a lot of good articles on the web. A recent one is http://www.diyphotography.net/getting-s ... ized-light. There's a detailed discussion of the theory HERE.

One important not mentioned in those discussions: if you're using polarized illumination and diffusion, you have to polarize after diffusion. Otherwise the diffuser will probably depolarize the illumination and then you're back where you started.

--Rik

[DQE]

Circular polarizers are recommended for general photography if one wants to use autofocus, as I understand it.

In the context of this thread, is the use of circular polarizers acceptable or necessary for DSLR-based setups? Is there any benefit from using linear polarizers for this application?

[rjlittlefield]

Circular polarizers are definitely acceptable. They may or may not be necessary. Linear polarizers often mess up autofocus and/or metering, and if you look very closely they can interact with the anti-aliasing filter on your sensor. That said, I'm still using linears because they're what I have handy. The demo/discussion at http://www.photomacrography.net/forum/v ... php?t=3945 was done with linears.

For polarizing the illumination, linear film has the advantage that it's much less expensive than anything circular.

From a theoretical standpoint, the key thing to remember is that the "front side" of a circular polarizer is just a linear polarizer. The "circular" part refers to what happens on the back side of the polarizer, where a quarter-wave plate changes the polarization pattern to essentially be spinning, with no preferred orientation.

--Rik

[rjlittlefield]

P/s: what are those white things inside the egg?

Those are markings on the caterpillar that is developing inside. They normally indicate that the caterpillar is close to hatching. But not always. Some species hibernate as fully formed caterpillars inside the eggshell. Those will not hatch until they get cues that spring has arrived.

--Rik

[jin]

You could use a polariser in front of the flash and another, rotated to minimise reflections, on the lens. Of couse, that will significantly reduce the intensity of the light reaching the lens.

Harold

Hi Harold,
will try as soon as a poloarizer sheet becomes available in near future. Placing it front of flash head is possible but not the objective due to space constraint.

One important not mentioned in those discussions: if you're using polarized illumination and diffusion, you have to polarize after diffusion. Otherwise the diffuser will probably depolarize the illumination and then you're back where you started.
Harold

Hi Rik,
thanks for the tip to repolarize if a defuser is placed infront of the polarizer.

Those are markings on the caterpillar that is developing inside. They normally indicate that the caterpillar is close to hatching. But not always. Some species hibernate as fully formed caterpillars inside the eggshell. Those will not hatch until they get cues that spring has arrived.

thanks for telling me 'marking' inside the egg - it hatched 4 days later, initially I thought it was prasited :-)

In the context of this thread, is the use of circular polarizers acceptable or necessary for DSLR-based setups? Is there any benefit from using linear polarizers for this application?

Hi Phil,
Since I'll not be able to place the polarizer front of the objective so I think the use of circular will not be applicable in this case.

[johan]

Hm, if space in front of the objective is an issue have you considered putting it between objective and sensor instead? How are you shooting, subject <= objective <= microscope <= camera or subject <= objective <= adapters <= tube <= bellow <= sensor? It might be worth trying an infinite setup to use the 'gap' to add extras like a pol