Ali Shah wrote:
>
> I should have said quality rather than "expensive"
> however, quality lenses tend to be pricey. When you
> refer to poor filters - such as the Hoya Green Label
> or the cheapy Sunpak, I know it can ruin the best
> photos. The HMC/SMC class Hoya's, BW's, Heliopan, etc
> tend to be better quality. On a WA Zoom with the
> element exposed the way it is...I wouldnt want to ruin
> that element.
>
You are a stubborn man, Ali. You apparently didn't read the suggested
reference and continue to generalize and make assumptions based on
price, reputation, etc.
"Please note that this particular filter is not indicative of Vivitar or
Vivitar VMC filters, in general. It just tested as a poor sample. Other
filter makers, even the most highly regarded, have been found to have
poor samples in selections taken from used and new stocks of filters.
The use of the term "poor" means star test images, viewed on a vertical
auto collimeter, which show images that are: multiple and overlapping,
fuzzy, off center, and images which rotate when the lens is rotated.
More often than not, only one of these faults are found in an examined
filter. These filters (including the test filter) often look
perfectly good when examined without the aid of instrumentation!"
Are you sure the fancy coated Hoyas use any different glass than the
cheap ones? Sure, B&W and Heliopan "tend to be better quality", so your
odds are better, but why take a chance?
With a digital camera, checking a filter takes only a few minutes and
costs nothing. Shoot a couple of images with good detail with and
without filter and do a little pixel peeping. With the camera tripod
mounted and a stationary subject, you can stack the images in layers and
readily see any differences. I personally would prefer a cheap filter
that has shown no image degradation to an expensive one that hasn't been
tested - less money, better odds.
Even at that, I simply don't use a filter unless in circumstances where
the lens might be at risk. One problem with digital is that the front
surface of the sensor assembly is much flatter than film ever is, and
may be shinier than most emulsions. So there is a problem with some
lenses of light reflected from sensor assembly to lens and back to the
sensor. I know its been a particular problem with some of the MF 90/x.x
macro lenses. Part of the process of adapting lenses for digital has
been ever more complex coatings to reduce this problem.
None of the surfaces in a lens are perfectly flat, but those of a filter
are intentionally very flat, and thus perfect mirrors. I wish I had
saved the url or image; I did see an example posted somewhere of a ghost
image in a night shot with a bright light in it that disappeared without
the filter. Hmmmmm, dark interiors of abandoned buildings with bright
sunlight shining through broken places, I wonder....
Moose
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