I was up near Dream Lake on Saturday for sunrise (which wasn't all that grand) and was early enough to try a star trail image. This image was shot a f/8.0 for 50 minutes. Canon 20D with 17-40mm lens.
Here are my questions. I can't remember where I set my focus. I thought it was on the tree, but I can't be sure. It was windy as heck up there.
1) Does this blur look to be wind related or is it improper focal distance?
2) Can you tell just by looking?
3) What should I be focusing on in the future?
4) Is f/8.0 about right?
Thanks for any help.
Cheers,
Alex
Posted by bill meikle on September 7, 2008 at 11:36 PM
Alex, since everything including the star trails seem soft it does feel that your focus was set incorrectly. Set focus to infinity in future for the stars at least?
The aperture you use depends on several things, if you are just shooting stars it should be fine, if you have a close object you will need to figure out your depth of field and set the F stop accordingly.
Posted by Brett Deacon on September 7, 2008 at 11:54 PM
Hi Alex. If the wind was anything like it was when I was at Dream Lake last weekend, it could definitely be a culprit. But I agree with Bill that focus is probably the main issue. I've discovered this to be a pain if your manual focus ring rotates slightly past infinity, which means you may have to visually verify the infinity focus point through a dark viewfinder. For what it's worth, I experimented with star trails a while back and got the most interesting (albeit noisy) results shooting at ISO 800 and f4. The image above probably would have been considerably brighter with a higher ISO and wider aperture.
Best,
Brett
Posted by Todd Caudle on September 8, 2008 at 12:34 AM
You should never EVER try to hand-hold a star trail shot. It just isn't gonna work.
I am by no means an expert on star trails (actually quite a novice) but I did spend a lot of time this summer experimenting with star trail photography. I found the following website to be the most helpful when practicing. As my first star trail photo turned out nearly a carbon copy of yours, I would say that it is definately the focus. I would guess that you were correct and focused on the tree. Where the focus should have been set for the stars to be in focus is at the "hyperfocal" distance of your lens. Many lenses have this area marked on the lens with small green brackets on the manual focus scale of your lens (yours may not be this way but my 28-135 Canon is). The hyperfocal distance is not necessarily focused at infinity either...as many new lenses will focus beyond infinity (bizarre concept, I know). I first set my lens at infinity thinking that would focus the stars but that was not the case at all. What I found that makes focusing easier is to set your lens at AF and focus on the moon (if there is one) and after the lens finds focus switch the lens to MF and then be careful not to touch the focal ring. If there is no moon you can focus the lens on a far away object in the distance before the light fails.
Anyway, that is my knowledge of star trails in a nut shell, the hyperfocal distance was the key element for me to take these types of pictures in focus. I believe if you read the article below it will help shed some light on your questions, it helped me a ton. If there is anything else I can help with let me know!
Sorry, forgot to add that this is one of my "successful" star trail shots, successful meaning that it is in focus. It is not that great of a photo but it was pretty exciting to see one in focus after being frustrated up all night.
One thing I forgot to mention is check and see if the 20D has a noise reduction setting on the menus, this will allow you to keep your ISO low. The image of mine above is taken at f/4 as the article I mentioned recommends, with ISO at 200 for 30 minutes. Just bare in mind that if you take an image of 30 minutes with noise reduction on it will actually take 60 minutes to process (the first 30 being the actual exposure, the second 30 a dark shot taken for noise reduction).
Anyway, my 2c worth, if I can give you any more info, I will be glad to.
Todd - sorry I forgot to put it in the post but this was on a tripod (but I'd be impressed if I could hand hold a 50 minute star shot and get it this sharp )
Thanks again,
Alex
Posted by bill meikle on September 8, 2008 at 11:08 AM
thanks for the url Alex, cool stuff.
Posted by John Mumaw on September 8, 2008 at 7:22 PM
Actually, the 'noise reduction' feature for long exposures is a 'dark frame subtraction', where the camera's software maps hot pixels from the long exposure and eliminates them. It doesn't do a thing to reduce/eliminate noise.
The key to keeping noise down is to take these long exposures when it's a cold evening.
Less heat on the sensor = less noise.
The image I posted above was taken last April when the ambient temp. was 30°.
It's a 3.5 hour exposure mated with a 3.5 hour dark frame subtraction. I slept through the entire episode, with my alarm set so I could close the shutter and let the DFS take over.
I used a Canon 40D with a 24-105 lens @ 35mm. I focused on the arch itself.
In order to get that length of time, I used a Canon ACK-E2 adapter and a small portable battery powered generator.
I wanted an ISO of 100 and an aperture of f5.6, but sadly I accidentally changed the settings on the camera to ISO 400 and f18 as I tripped the shutter in the dark, which botched my experiment.
Still, it turned out well enough for a Web presentation (I think).
This was my very first attempt at photographing star trails.
Anyway, my point is to keep experimenting!
Posted by Cynthia Spence on September 10, 2008 at 4:58 PM
Nice shot John!
My experience with star trails is that the same f stop rules apply...lots of depth of field then use a higher f stop...if what you need to focus on is at infinity then use a lower f stop. of couse the lasts trails I took were with film...and I've kept my film camera just in case I want to take future star trail shots...film works well and a new set of batteries usually lasts long enough in a film camera. I've heard there is a program that will interpolate the trails once you've taken a reference shot, it then fills in the trails for you...this is to help with the digital noise problem. Never seen a photo yet that has used it.
Discussion
9 repliesI was up near Dream Lake on Saturday for sunrise (which wasn't all that grand) and was early enough to try a star trail image. This image was shot a f/8.0 for 50 minutes. Canon 20D with 17-40mm lens.
Here are my questions. I can't remember where I set my focus. I thought it was on the tree, but I can't be sure. It was windy as heck up there.
1) Does this blur look to be wind related or is it improper focal distance?
2) Can you tell just by looking?
3) What should I be focusing on in the future?
4) Is f/8.0 about right?
Thanks for any help.
Cheers,
Alex
The aperture you use depends on several things, if you are just shooting stars it should be fine, if you have a close object you will need to figure out your depth of field and set the F stop accordingly.
Best,
Brett
(your focus is off...)
I am by no means an expert on star trails (actually quite a novice) but I did spend a lot of time this summer experimenting with star trail photography. I found the following website to be the most helpful when practicing. As my first star trail photo turned out nearly a carbon copy of yours, I would say that it is definately the focus. I would guess that you were correct and focused on the tree. Where the focus should have been set for the stars to be in focus is at the "hyperfocal" distance of your lens. Many lenses have this area marked on the lens with small green brackets on the manual focus scale of your lens (yours may not be this way but my 28-135 Canon is). The hyperfocal distance is not necessarily focused at infinity either...as many new lenses will focus beyond infinity (bizarre concept, I know). I first set my lens at infinity thinking that would focus the stars but that was not the case at all. What I found that makes focusing easier is to set your lens at AF and focus on the moon (if there is one) and after the lens finds focus switch the lens to MF and then be careful not to touch the focal ring. If there is no moon you can focus the lens on a far away object in the distance before the light fails.
Anyway, that is my knowledge of star trails in a nut shell, the hyperfocal distance was the key element for me to take these types of pictures in focus. I believe if you read the article below it will help shed some light on your questions, it helped me a ton. If there is anything else I can help with let me know!
http://www.danheller.com/star-trails.html
Sorry, forgot to add that this is one of my "successful" star trail shots, successful meaning that it is in focus. It is not that great of a photo but it was pretty exciting to see one in focus after being frustrated up all night.
One thing I forgot to mention is check and see if the 20D has a noise reduction setting on the menus, this will allow you to keep your ISO low. The image of mine above is taken at f/4 as the article I mentioned recommends, with ISO at 200 for 30 minutes. Just bare in mind that if you take an image of 30 minutes with noise reduction on it will actually take 60 minutes to process (the first 30 being the actual exposure, the second 30 a dark shot taken for noise reduction).
Anyway, my 2c worth, if I can give you any more info, I will be glad to.
Thanks for the links and the advice - darn focus.
Todd - sorry I forgot to put it in the post but this was on a tripod (but I'd be impressed if I could hand hold a 50 minute star shot and get it this sharp
Thanks again,
Alex
The key to keeping noise down is to take these long exposures when it's a cold evening.
Less heat on the sensor = less noise.
The image I posted above was taken last April when the ambient temp. was 30°.
It's a 3.5 hour exposure mated with a 3.5 hour dark frame subtraction. I slept through the entire episode, with my alarm set so I could close the shutter and let the DFS take over.
I used a Canon 40D with a 24-105 lens @ 35mm. I focused on the arch itself.
In order to get that length of time, I used a Canon ACK-E2 adapter and a small portable battery powered generator.
I wanted an ISO of 100 and an aperture of f5.6, but sadly I accidentally changed the settings on the camera to ISO 400 and f18 as I tripped the shutter in the dark, which botched my experiment.
Still, it turned out well enough for a Web presentation (I think).
This was my very first attempt at photographing star trails.
Anyway, my point is to keep experimenting!
My experience with star trails is that the same f stop rules apply...lots of depth of field then use a higher f stop...if what you need to focus on is at infinity then use a lower f stop. of couse the lasts trails I took were with film...and I've kept my film camera just in case I want to take future star trail shots...film works well and a new set of batteries usually lasts long enough in a film camera. I've heard there is a program that will interpolate the trails once you've taken a reference shot, it then fills in the trails for you...this is to help with the digital noise problem. Never seen a photo yet that has used it.