Shot at f22

[batch]

I used f22 for this shot for two reasons, 1) i wanted the the lights on the wharf to have that star sparkle, 2) the sea was quite choppy so i wanted to smooth it out. It was about 20min's before sunrise so there was some light around.
A few questions i have about this shot if anybody can help me with
1) What would be the best aperture to use turning bright lights into a star, and if anyone knows why does it only create a star with 6 points and say not 8
2)Using f22 can soften the detail, does this change if you use a long exposure
3) Filters for a 10-22 lens, i have cokin filters but they cause a lot of dark shadow around the edge of the images, can anyone suggest what i could use to make better use of this lens

Exposure: 30
Aperture: f/22.0
Focal Length: 10 mm
ISO Speed: 200
Exposure Bias: 0 EV


I found another image but using f10, the star effect on the lights are not as sharp

Exposure: 13
Aperture: f/10.0
Focal Length: 13 mm
ISO Speed: 200
Exposure Bias: 0 EV

[CaptainNH]

Firstly, beautiful shots - I particularly like the composition in the first shot.

Originally Posted by batch

1) What would be the best aperture to use turning bright lights into a star, and if anyone knows why does it only create a star with 6 points and say not 8

The beauty of using small apertures to produce star-burst is that you can control the size of the star-burst by changing the aperture - the smaller the aperture, the bigger the flare. Experimentation is the key.

The number of points on the star depends on the number of aperture blades in your lens - the 10-22mm lens has 6 blades, hence 6 points. Apparently, if you have an odd-number of blades, you get double the number of points, but I've never tested it. Can anyone with a 50mm f/1.8II (which has 5 blades) confirm?

Originally Posted by batch

2)Using f22 can soften the detail, does this change if you use a long exposure

Provided you have a solid tripod, generally no. The sharpness of lenses suffers at small apertures, but that is a physical effect of the lens construction, not the decreased shutter speed. You will introduce some noise into the image with extended exposures though - the extent is dependant on the ISO and the camera.

Originally Posted by batch

3) Filters for a 10-22 lens, i have cokin filters but they cause a lot of dark shadow around the edge of the images, can anyone suggest what i could use to make better use of this lens.

What you're seeing is probably vignetting - you're seeing the edges of your filter in your shot as a result of the ultra-wide angle lens. See if it disappears if you zoom in tighter. The 10-22mm is generally prone to vignetting at 10mm anyway. If it bothers you, you can always devignette in post-processing.

You don't say if you're using Cokin screw-in or the "Creative System" type filters. Ultra-wide lenses need either thin screw-in filters (which generally have no thread on them - you'll lose the ability to stack filters or fit a lens cap) or the Creative System holder for resin filters (probably a Z size for the 10-22mm lens).

There's been some discussion of this recently - Grad ND Filters

[CaptainNH]

Originally Posted by CaptainNH

The number of points on the star depends on the number of aperture blades in your lens - the 10-22mm lens has 6 blades, hence 6 points. Apparently, if you have an odd-number of blades, you get double the number of points, but I've never tested it. Can anyone with a 50mm f/1.8II (which has 5 blades) confirm?

Probably bad form to answer your own questions, but I realised that I had my 50mm 1.8 with me.

A quick two minute experiment revealed that the 5-bladed 50mm gave me 10 points, the 8 bladed 85mm f/1.8 gave me eight points.

[batch]

Thanks Neil for the compliment, and responding to my questions so comprehensively. The filters i have are the resin slide in. I think the holder and the filter may be to small for the lens but didn't want to spend money on something that wasn't going to work.

[milosh]

Wow, great composition and exposure in the first photo!

I just wanted to add, maybe you already know this, that you can get a wide angle Cokin P series holder (it holds only one filter instead of three). Many people say that they use the wa holder with Sigma 10-20 without significant problems.

[BryanC]

Originally Posted by CaptainNH

Probably bad form to answer your own questions, but I realised that I had my 50mm 1.8 with me.

A quick two minute experiment revealed that the 5-bladed 50mm gave me 10 points, the 8 bladed 85mm f/1.8 gave me eight points.

A little side info about why this happens: When there's an even number of blades, each point where blades meet have another point directly across from it. So, what happens is that the spikes from these points opposite each other overlay, making 2 look like 1. When there's an odd number of blades, there aren't points directly across from each other, no overlaying, so you see all of the spikes from each point. Technically, an 8 bladed lens does have 16, but you only see 8 because of the pairs that overlay on top of each other. Hopefully, I made some sense with this explanation...

[milosh]

Originally Posted by BryanC

A little side info about why this happens: When there's an even number of blades, each point where blades meet have another point directly across from it. So, what happens is that the spikes from these points opposite each other overlay, making 2 look like 1. When there's an odd number of blades, there aren't points directly across from each other, no overlaying, so you see all of the spikes from each point. Technically, an 8 bladed lens does have 16, but you only see 8 because of the pairs that overlay on top of each other. Hopefully, I made some sense with this explanation...

Thanks for this, I was wondering what's going on in there..this makes perfect sense now.

[OsmosisStudios]

Then you can get things like this, where the flare doesnt quite overlap

[jojonac]

This is why I love DPS...I have known for the last two years about the effect you can get with high aperture...I just didn't know why!

Thanks guys