how can I avoid these circles in night pics?

[jfred]

Hi All. Just had my EOS 20D for a week, so still... "experimenting" when time and work permit.

Took a couple of night shots yesterday near my house, because night scene photos are something I'm, interested in. (this isn't the most scenic shot I could have taken... just something to test the equipment without me having to walk too far!)

Just using the standard 18-55 EF lens with a skylight filter on (I always have a neutral filter on my lenses... just in case... not sure if this is a wise precaution or not)

Hugely impressed with the results, (2.5sec at f5, ASA 100, parameter set1, zoom at 42mm) but - there were strange circular patterns visible on the picture from the centre outwards (cropped and shrunk version attached). Is this caused by reflections within the lens, or the fact that there was a bright light somewhere in the picture?

Thanks in advance for any thoughts!

[Eric DeCastro]

from what I know, skylight is different then UV(0) have you tried to take the filer off then take the picture?

[jfred]

not yet! will give it a go tonight/tomorrow (assuming lack of rain outside!) and see if it helps

[T_O_M]

Had the same problem when shooting with a Tokina 19-35 with UV filter at night. Took the filter off and flare was gone.

[tim]

Hey jfred, you know me from another board ;) I'd try what Tom suggested to, and report back what you find :)

[Spod]

Hi JFred.

I had a similar problem appear on my 10D as you can see from the pic below. All the shots taken in Tate Modern suffered from the same circular distortion, but all the shots I took at the aquarium later the same day were not affected.

I've never had the problem since.

Exposure parameters where similar at both locations. The lens used for all the shots was a 24-70L with a Hoya Pro1 UV filter.

I put it down to either electrical interferance - there was a loud, deep electrical buzzing noise in the Tate Turbine Hall, or acoustic interferance - I could feel the buzz in the walls, floor, handrails and also in my body.

Of course, I've no real idea what's causing it and therefore can't help you, but I just thought I'd let you know!

[jfred]

Thanks for all the responses. I was wondering also, whether it was down to any processing the 20D was doing based on the "parameter 1" settings. Probably not, but a thought anyway.

so I plan to try:
- shooting without the filter in place
- collecting raw images as well as jpgs
- trying one or two different locations/angles and see what the results are.

[mr.photoguy]

I once did a night shot with my 20D, but used my 50mm lens.
This was the result.
http://www.pbase.com/brucescott/image/37572138/medium.jpg

I don't use any filters on my 50mm ..

I have never seen those ripples before, but I figure they may be from you using the skylight filter.
With using the long exposure, the camera may have had enough time to adsorb the ripples from off of the filter.
Aren't skylight filters mainly meant to be used in the day time?
That's something for me to look into ..
cya

[scottbergerphoto]

The top picture shows a long exposure caused by the mostly dark background resulting in overexposed lights. The highlights get clipped and the highs all blend together. The same thing is happening in the second picture.
The bottom picture shows the diaphragm blades as a result of a very small aperture and long exposure.
Scott

[attu]

scottbergerphoto, what they are talking about is the circular rotating rings in the photos as can be seen in the bottom corners of the first pic and in the top middle of the second pic, I cant see any in the third pic.
I was going to say it was due to using a low quality UV filter but as Spod was using a Hoya Pro1 UV filter on a high quality lens I guess my theory goes out the window :)

Andy

[Citizensmith]

Whenever you have point sources of light you need to be carefull. A filter on the front can be a big problem as it will cause all kinds of patterns as light passes through it, and light reflected back off the sensor re-reflects off the back of the filter. It's a good time to take a filter off basically.

The stars around lights in one of the other photos are a result of shooting at a high apperture (f16 or greater). The number of points you get is dependant on the number of blades the apperture mechanism has.

[jfred]

ok - tried again tonight without the filter (too tired to post pics, will try to catch up tomorrow or so)

no circles :) Hooray!!!

As a matter of interest, I also tried a couple of comparison night shots with my A80 on the tripod as soon as the 20D came off (don't laugh). I need to look at the pics again in more detail. The results from the 20D without the filter are... pretty damn good. The A80 results (I used manual control and the same ISO/Metering settings as the 20D, because the metering system couldn't cope!) ... were... surprisingly good too.

Anyway.. I'm glad I know what to do for next time.. and thanks for all the feedback/responses :)

[Cash--]

ahh.....thats good info.......

I took some shots of the moon the other night, and it had halo type flare stuff goin on, never really thought about the filter.....

[DocFrankenstein]

Hi JFred.

I had a similar problem appear on my 10D as you can see from the pic below. All the shots taken in Tate Modern suffered from the same circular distortion, but all the shots I took at the aquarium later the same day were not affected.

My best bet is that you used a high aperture. f/22 or f/32 maybe? It produced a circular diffraction pattern.

How many blades does 24-70 have?

[T_O_M]

Cash--

The halo effect you get when shooting the moon is the over exposure of the moon and or blur. Try using the old film photograpy lunar 11 rule. Put your camera in manual set your aperture to f11 and your shutter speed to 1/iso speed (iso 100=1/125).

[forrest64]

how can I avoid these circles in night?

Try a different brand of Whiskey?

[Spod]

My best bet is that you used a high aperture. f/22 or f/32 maybe? It produced a circular diffraction pattern.

How many blades does 24-70 have?


The shot was taken at f4, 1/80. Not sure how many blades the 24-70 has - 9 I think, but maybe 7.

The thing I find most curious is that I've never seen it again on my camera and I leave the filter on all the time!

[Jon]

I once did a night shot with my 20D, but used my 50mm lens.
This was the result.
http://www.pbase.com/brucescott/image/37572138/medium.jpg

I don't use any filters on my 50mm ..

I have never seen those ripples before, but I figure they may be from you using the skylight filter.
With using the long exposure, the camera may have had enough time to adsorb the ripples from off of the filter.
Aren't skylight filters mainly meant to be used in the day time?
That's something for me to look into ..
cya

I'd suspect those wavy lines are from car lights as they changed lanes, etc. during your exposure. Nothing to do with the filter.

Skylight filters are menat to cut out some of the UV and extreme violet light from your pictures to keep them from looking washed out under daylight conditions. If that light isn't present in your night shots, the filter won't have any impact on light transmission. BUT a poorly-made, scratched, or un/single coated filter can distort the image as the light rays go through it, day or night. I just added $700+ in filters (UV-0 and CP) to my B&H wish list so I've got consistent filters on all my lenses. And that amount's going to go up when I add the right number of each size onto the list . . .

[mr.photoguy]

I'd suspect those wavy lines are from car lights as they changed lanes, etc. during your exposure. Nothing to do with the filter.

. . .
Yes, I know .. A car drove by at about 5mph and created the wave of light.
It was done on purpose.

[Jon]

Yes, I know .. A car drove by at about 5mph and created the wave of light.
It was done on purpose.

Your post, in the context of this thread, suggested otherwise, or at least that you had a question about it.

[mr.photoguy]

Your post, in the context of this thread, suggested otherwise, or at least that you had a question about it.
Nope I was just showing one my night images as an example. (without a filter).
didn't mean to confuse anyone.