Author Topic: a300 Filter Questions  (Read 3988 times)

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Offline Genisis

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a300 Filter Questions
« on: July 18, 2009, 08:52:36 PM »
  Just starting to get some of the filters I need to take some good pics.  I have a bought a UV Filter, circular polarizer and a 75/300 lens.
  The question I have is, should you use the two filters together or are they really meant to be used separately?  The salesman that I got the  polarizer from stated that you can use them together.  However, when I did...the shot seemed darker to me than it should have been.  Settings were all auto and I was outside on a clear sunny day....just seemed to dark.
  Any suggestions on the correct use of the filters will be appreciated.  Thanks!

Offline Rob aka [minolta mad]

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Re: a300 Filter Questions
« Reply #1 on: July 18, 2009, 09:22:35 PM »
You can use them together, the images wouldnt be darker though, as the camera should compensate for the light reduction that the filter causes.

When you say the shot was darker this would have been down to where the camera was metering from rather than the filter.

Was all the image dark or just some of it, ie was the brighter parts of the image ok (lik the sky, for example) and the rest of the image dark ???


Rob

Offline Faldrax

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Re: a300 Filter Questions
« Reply #2 on: July 18, 2009, 09:27:22 PM »
You can leave the UV in place, but there is no advantage to doing so, and it might reduce the quality of the final shot be being there (there are endless discussions on the various forums on the merits of leaving a UV on lenses or not).

Personally I always take the UV off when I fit a polariser on - in part that is to avoid vignetting - where the corners of the final shot are darkened by the shadow from the filter rim. I have spent the extra to get a specially thin polariser, so to stack it with a UV seems the wrong thing to do :-)

A CPL will (as a side effect) drop the light by (I think) 2 stops, but the cameras exposure meeter should automatically adjust for this and just mean a larger aperture / slower shutter to compensate.

Note: Rob replied while I was typing, but thought I might as well post anyway, to confirm what he said:-)
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Offline Genisis

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Re: a300 Filter Questions
« Reply #3 on: July 18, 2009, 09:38:00 PM »
This pic is with UV filter only


This pic is with UV Filter and Circular polorizer


Letting the pics speak for themselves here....so, from what I gather from Faldrax...it does appear to have dropped my light by about 2 steps.  Dont know hwy the camera didnt compensate.

Any ideas from seeing the pics?  Im leaning towards using them separately.

Offline Rob aka [minolta mad]

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Re: a300 Filter Questions
« Reply #4 on: July 18, 2009, 10:19:31 PM »
Using them separately wont make any difference to exposure, and regards to quality if have always used my polariser on top of my UV filter and have never noticed any degradation of quality.

Looking at the images i still say that the camera has metered from differant places as the top image the houses are alot higher up that the bottom image.

Without doing a proper test its impossible to be certain what has gone on.
What you need to do is to mount the camera on a tripod and take an image with and without the polariser attached, keeping the settings the same ie in auto or A priority, set your camera to centre weighted metering and i'll guarantee that the images will be the same.


Also you have got dust on your sensor.


Rob

Offline Genisis

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Re: a300 Filter Questions
« Reply #5 on: July 19, 2009, 12:46:12 AM »
  Thanks for all or replies so far.  Im going to just that.  I will put it on a tripod and give it a good steady test and see.  Thanks again.

Offline chappo1

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Re: a300 Filter Questions
« Reply #6 on: July 19, 2009, 01:18:53 AM »
What exposure metering is your camera set to?  Matrix, centre weighted or spot?
If you have it set to matrix metering and you have more sky then the camera will compensate and the houses will be darker.
As you gain confidence you can try setting the camera to aperture priority (where you control the depth of field) and to spot metering where you point the spot to the area you want metered (push the button down half way to lock in the exposure) and then recompose the shot.
This will be irrespective of the filters you are using.
I recommend that with your camera on the tripod you do some experiments with the settings (remember to note down what you changed in a notebook) and evaluate the results.  It is a great way to learn....john
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Offline winjeel

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Re: a300 Filter Questions
« Reply #7 on: July 19, 2009, 02:45:41 AM »
I think the main problem is the camera setting: "auto". I had a quick look at the exif data, and it says that the exposure was set on auto and so was the white balance. The 1/160sec shutter speed is fine, but f10 aperture could be knocked down a little, to maybe f9 or f8. I feel that perhaps you were shooting into the sun a little, perhaps without a hood on. Also, I think that possibly the polariser might have fooled the auto white balance. If it was set for sunny, then the colours might be just that bit more vibrant than what they are. If you want more info on this, check out my How To guide here. Hope this helps.
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Offline pointblank

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Re: a300 Filter Questions
« Reply #8 on: July 19, 2009, 04:37:58 AM »
I noticed another significant issue, the position towards the sun under which the polarizer was used; for the best effects the sun is at 90 degrees of your viewpoint.

The polarizer will increase the total exposure time but on a normal bright day you should be able to easily get away with it. Metering is important as well as otherwise the shot will indeed be unbalanced as chappo1 is mentioning up here. Check the link below for reference on this filter.

http://www.great-landscape-photography.com/polarizing-filter.html

By the way, you got a few dust spots inside your camera, I can spot 3 easily. Oh, regarding the UV filter, it will not have any effect apart from protecting your lens (but your polarizer does that for you now). All digital camera's are designed to ignore UV light.
« Last Edit: July 19, 2009, 04:40:10 AM by pointblank »

Offline winjeel

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Re: a300 Filter Questions
« Reply #9 on: July 19, 2009, 05:23:08 AM »
I think I need to clean my monitor, as I missed those spots, Pointblank. :) But you're right, I can see them now. I've gone to the top of this page and typed in the Google Search "sensor cleaning" and this was the first page I found. Hope it helps.
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