Fli, Fla, Flare
Posted 15 July 2003 - 05:38 AM
I read about the flare issues related to the sigma lenses in some threads.
Now i tried it myself with our brand new sigma 28-300mm f3.5-6.3 DL
Aspherical IF Hyperzoom. I just gave it a try in the sunset to check if this
is a problem with all sigma lenses and not only with the wide angle ones.
here you can see some results, which are at least for me a bit disappointing
I mean i haven't expected flares which are not round at all as you can see it
in the first picture on the left side.
here is a nice one but it has this odd green flare on the left side:
So my question is if anybody knows how to control the flare effect
a bit, apart from not shooting into the light
Looking at the exif data i guessed that the aperture might control the
size of the rings? But its just guessing?
Posted 16 July 2003 - 01:32 AM
Posted 18 July 2003 - 11:39 PM
Stupid me... I can't figure out how to add the image to my post (what a neophyte) Any direction to a how to section would be most appreciated.
Posted 19 July 2003 - 03:55 AM
lens flares are created by directly shooting into a light source. As long as the flash unit isn't
in front of the lens it isn't the source for any flare effect B)
There are two different types of flares. The first which causes the rings or circles and the other
which produces the streaks around the light source.
As far as I could figure out the lens flare depends on the combination of the following things:
1. the angle of the light source to the camera
2. the number of optical elements in the lens
3. the number of aperture blades
4. the material of the optical elements of the lens
5. the cleaness of the lens
(6. the aperture)
1. The cause of the lens flare is that some parts of the light are reflected at the edge of the
optical elements of the lens instead of going through it. These reflections create new light
sources. Every element between the light source and the film or ccd can cause reflections
and can so create new light sources which than result in flares.
2. With the number of the lens elements the number of flare rings or circles within the picture
will grow as well. This means a zoom lens will create much more flare rings then a normal lens.
3. The streaks around the lights source are depending on the number of aperture blades used
in the lens. As the area where two blades are more reflective then others this will create
additional light sources forming the strikes. As you can see on my last image the sigma lens
uses 8 aperture blades resulting in 8 strikes. You can only see the lower one, but can easily
imagine, that the lower one can be mirrored. The upper one can hardly be seen because the
sky is too bright.
4. The material of the elements is important as well. Different glasses causes different reflections.
This is the reasons why the lenses are different in price i guess . Zeiss for examples produced
a glass with a coating which almost reduced all reflections on the lens parts. This where then
used from the nasa to take pictures from the sun.
5. If you have dirt on the lens this produces reflections as well which then can cause some flare.
So my conclusion is if you want to prevent the flare dont shoot into a light source. If you still want
to capture the light source try to shoot with a big aperture number e.g. 20. this reduce the light
going the the lense and there reduce the number of reflections. But i can't prove this so far. If anybody
has any ideas about this, I would like to hear it.
After reading some about the flare effect I still wonder how this bubble flare could be created on
my first image. Normally the flare are circles and not these. I do not know how to describe this
correctly but look at the left bottom of the image.
Posted 19 July 2003 - 06:55 AM
Thanks for the flare info.
Can you direct me to a place where I can learn how to add images to my posts? I haven't found any place in the wetpixel site that explains this?
Posted 19 July 2003 - 07:06 AM
I do not know any links where this is explained , but it's not that hard .
The only thing you need is some webspace where you can put your image.
Then you can use the [img] button and enter the url of the picture and the
image will be included in the text.
In my case I put my images on my webspace at the university server and
then linked to it with the img button.
I didn't tried the upload function for attachments so far. I guess then you
only get a download link in your text instead that the picture is displayed.
Posted 20 July 2003 - 08:27 PM
to reduce flare. It helps a lot.
Dual Ikelite Strobes
Photo site - www.reefpix.org
Posted 03 August 2003 - 10:46 PM
Posted 04 August 2003 - 02:01 AM
Posted 07 August 2003 - 04:57 AM
My guess is that stray light is getting into the port to cause the reflection. Does your dome port have a shade on it? Is the back of the dome (the flat part) black? It should be. All should be 'blacked out' except for the front of the dome.
Dual Ikelite Strobes
Photo site - www.reefpix.org