Help with night shot

tripwater · Oct 30, 2009

Tonight where I live there is a mist in the air. I came across a cemetery with a lit cross. I noticed across the street, a street lamp offered a dark orange contrast to the light blue of the cross. Almost like good and evil.

1/13 sec at f2.8 ISO 100. Canon 50D with Tamron 90mm macro lens ( only lens I have at present )

I am happy with the shot itself but wondering what the deal is with the dithering rings around both lights fading into the blackness? I know that compressing to a jpg will cause some of this but my raw file seems to have this to a lesser extent when viewing in Lightroom.

Any thoughts on how to avoid this or clean this up in post? I would really like for the light to fade into the darkness and not have dithering rings

Thanks

( I apologize for the large image size, I just wanted to be sure that the dithering I am pointing out was noticeable.)

musicaleCA · Oct 30, 2009

This is caused by your wide-open aperture. What you're seeing is how the lens renders point-light sources wide-open. Best bet is to stop down to somewhere in the middle of the range like f/8-10 to lessen that. Go further and you end up with long lines extending from point light sources, the number of which is equal to the number of aperture blades in the lens.

ssnxp · Oct 30, 2009

musicaleCA said:
This is caused by your wide-open aperture. What you're seeing is how the lens renders point-light sources wide-open. Best bet is to stop down to somewhere in the middle of the range like f/8-10 to lessen that. Go further and you end up with long lines extending from point light sources, the number of which is equal to the number of aperture blades in the lens.

I'm not the OP, but thanks! Good to know. :thumbup:

tripwater · Oct 31, 2009

musicaleCA said:
This is caused by your wide-open aperture. What you're seeing is how the lens renders point-light sources wide-open. Best bet is to stop down to somewhere in the middle of the range like f/8-10 to lessen that. Go further and you end up with long lines extending from point light sources, the number of which is equal to the number of aperture blades in the lens.

This is very interesting. Thank you for the info, I will keep that in mind!

Stil on teh subject of graininess, last night as an experiment, my roommate and I took some shots of wine glasses with a light box and blocking off light to everything but the glass edges. Even at 1/8 sec f32 ISO 100 we noticed a considerable amount of grain in our shots. We even swapped lenses to his lens and same result. For some reason no matter what the aperture, I am getting a bunch of grain in my shots in low lighting. I see other people's night shots of cities and and silhouette shots they seem black where black needs to be not pixelated and grainy. Most of the grain it seems to me is in the gradient blending from dark to lighter areas. This may be something I can't fix in camera and just be part of art but would like to know.

Now I will preface by saying this picture was one of the best out of the series. Many were much worse depending on how the light hit the glass. Maybe I am expecting too much here but would like to know none the less

Here is one of the shots we took:
This one was at f11. We took another at f32 and got the same results

Here is at 100% crop

To me, this seems like the kind of result you should expect if you were shooting at a faster ISO of say 1600-3200. Again, I may be expecting too much but starting to notice a trend in my shots with low lighting and would like to learn how to fix this before I ruin some great opportunity shots!

musicaleCA · Oct 31, 2009

First, it's not grain, it's noise. Second, it's not bad in the shots above. Third, it's worse in shadow areas than highlights. Fourth, if you underexpose you will get considerably more noise. Fifth, that looks like a reflection in the glass, not noise. Sixth, lenses don't affect noise. Seventh, neither does aperture.