Views on retention or removal of antialiasing filter - spectrum enhanced DSLR mods

[rcheshire]

Hi. Just canvassing opinion about retaining or removing the anti-aliasing filter for spectrum enhanced DSLR mods. The question came up about soft focus with Canon cameras because of the strength of the AA filter. I guess referring to the low pass filter.

Yes, No, Doesn't matter, Not compatible with spectrum enhanced mods?

Thanks

Rowland

[Merlin66]

I have the FULL spectrum mod (both filters removed) on my 1000D which I use for spectroscopy.
The loss of focus when using standard camera lens is minor BUT with EF lens the astronomik MC clip in filter can be used to correct.
Unless you really need to access the UV below 400nm and the NIR above 700nm you can safely leave the front ant-alias/ dust shake filter in the camera.

[rcheshire]

http://www.canonwatch.com/eos-5d-mark-iii-hacked-anti-aliasing-filter-removed-more-sharpness/

I think this illustrates what I'm on about, although I don't own a MKIII.

[Merlin66]

Interesting.
I can't speak for the 5D III, but on the others, 450D through to the 1100D the front anti-alias/ dust filter acts also as a UV-IR cut filter. Removing it will increase the pass wavelengths into the camera and possibly cause UV or IR bloating in "normal" family photography.
Each filter (the Colour Balance filter - on the CCD, and the Anti-alias filter - at the front) is 1mm thick. So for each filter removed, you change the "body depth" by 0.3mm.
This change makes a minimal impact on the focus of standard lenses when only the Colour balance filter is removed i.e. normal astro mod.

[rcheshire]

I'm beginning to think it's best removed for astro mods.

[gregbradley]

Definitely removed. But you will also get moire in video shots. Moire in still shots in terrestial scenes with fine repeating patterns is less likely to occur than is often thought.

After using my Nikon D800E which has no AA filter for a while I would definitely prefer a non AA camera over an AA camera in the future.

But it does come down to your use of the camera. Some cameras are better suited for some uses than others. Much like telescopes that way.

Some cameras try to appeal to all users but in the end their is a bit of a compromise for all in that scenario.

As far as UV/IR filter goes, isn't that the culprit for reducing Ha sensitivity as DSLR UV/IR filters cut off too early and reduce Ha?
Astrodon has an article about these. He now sells his replacement UV/IR filter.

I am not 100% sure now as when I modded DSLRs it was before the dust shaker models with 2 filters.

If I were a wedding DSLR videographer I would want the AA filter for sure as moire would damage many of your scenes.
For general wedding photography it would be an issue only occassionally and I would have to test to know for sure. I have taken about 700 shots with my D800 and seen moire only about 4 times so far. So moire is clearly overrated except for video where it is a big issue.
I took a few videos of cityscapes and the moire is bad bad bad, but less so when you increase the size of the video. But video of landscape would be totally fine. Also moire is a bit weird. You can look at an image at one size and it has bad moire, you then increase the size of the image only to see no moire in the image at all. So it seems your computer monitor can show moire when there is none in the image.


Greg.

[Merlin66]

Greg,
The loss of the Ha responce is due to the Colour Correction filter, not the AA/ Dust filter.
Filter #1 curve is the AA/Dust filter
Filter#2 curve is the Colour Correction.