| Author | Thread |
|
|
01/31/2006 05:04:46 AM · #1 |
Well, after having it for several weeks and just taking snaps around the house to get the feel of it -- I final had the chance to take my new D70 out for a real-world test drive. I've seen the night shots that have been posted in the past couple of months, and have wanted to try my hand at it -- so that is what I did. I walked up to the lake near about a mile from my house and tooks some images. This was after 11:00 pm (5+ hours after the sun had set).
I was cold so I wasn't out very long -- and these images have had no post-processing other than default raw conversion, resize and save for web. All were shot without a tripod, with the camera sitting on something. The settings for all three were ISO 800, f1.8, 25 sec.
Next time I'll take my tripod and remember to use the timer (many were spoiled by shake as I pressed the button). I'll also buy a cheap stop watch and use bulb mode to give a longer shutter speed so a lower ISO can be used. But that was the intention when I went -- to know what I needed to do next time to make it better.
The reason I'm posting them is that I have some questions on how to do this better. Here's a sample:
  
the questions
In all of them, so some degree, in the upper left hand corner there is a purple glow -- What is it? what causes it? ... and, most importantly, how do I prevent it?
In the last one, there are 3 vertical curved stripes (top, middle-right). This is the only image of the set they appear in. If it's important, it is the southern sky. What are they?
David
/edit: clarity
Message edited by author 2006-01-31 05:23:59.
|
|
|
|
01/31/2006 05:11:53 AM · #2 |
Originally posted by David.C:
In all of them, so some degree, in the upper left hand corner there is a purple glow -- What is it? what causes it? ... and, most importantly, how do I prevent it?
|
Some 25s shots with a DSLR...Perhaps you forget to close the optical viewfinder? Light also enter there. |
|
|
|
01/31/2006 05:18:00 AM · #3 |
Hi David - maybe some bad news. I've found exactly the same thing
About 11 minutes exposure at F8 ISO200, exactly the same glow, exactly the same place.
I noticed it on some previous shots and tried to close every hole, but it remained there.
My brother-in-law did some star-trails with his D70 over the week-end, will check with him if he's seen the same thing. |
|
|
|
01/31/2006 05:25:23 AM · #4 |
The purple glow is heat gain on the sensor in the corner where it is closest to the heat-generating part of the camera workings. It's a known problem. You won't notice it anyway if you process these to look more night-like, probably, and if you DO you can isolate the area and remove the color cast pretty effectively.
You talk about using bulb and a stopwatch; you DO have a remote release, right? If not, you have to get one; you cannot avoid camera shake in bulb mode without one.
Robt. |
|
|
|
01/31/2006 05:28:35 AM · #5 |
Originally posted by Gabriel:
Originally posted by David.C:
In all of them, so some degree, in the upper left hand corner there is a purple glow -- What is it? what causes it? ... and, most importantly, how do I prevent it?
|
Some 25s shots with a DSLR...Perhaps you forget to close the optical viewfinder? Light also enter there. |
New to DSLR, so I never even thought to close it -- it came with a cap for it though -- I'll try that next time.
thanks.
Originally posted by wsteyn:
Hi David - maybe some bad news. I've found exactly the same thing
About 11 minutes exposure at F8 ISO200, exactly the same glow, exactly the same place.
I noticed it on some previous shots and tried to close every hole, but it remained there.
My brother-in-law did some star-trails with his D70 over the week-end, will check with him if he's seen the same thing. |
Thanks
David
|
|
|
|
01/31/2006 05:40:09 AM · #6 |
Just for the heck of it, here's a quick remake of the first one in PS. Minimized but did not eliminate the magenta, need a higher-res image to do it properly.
R. |
|
|
|
01/31/2006 06:50:14 AM · #7 |
Originally posted by Bear_Music:
The purple glow is heat gain on the sensor in the corner where it is closest to the heat-generating part of the camera workings. It's a known problem. You won't notice it anyway if you process these to look more night-like, probably, and if you DO you can isolate the area and remove the color cast pretty effectively. |
Thanks. So it's something I have to learn to handle in PP instead of during the shoot -- not exactly what I was hoping for, but I can live with it. ;)
Any idea what the lines are in the third image? My first reaction was they reminded me of the satalites I use to watch while sitting on a bridge with some friends when our college schedule permitted. But I quickly discounted that since they are north-south lines and satalites (if I recall correctly) would be east-west. That, and I don't think a satalite would be in the scene long enough to create a noticable trail. Could be wrong though.
Originally posted by Bear_Music:
You talk about using bulb and a stopwatch; you DO have a remote release, right? If not, you have to get one; you cannot avoid camera shake in bulb mode without one. |
Remote is on order -- should be here by the weekend.
Originally posted by Bear_Music:
Just for the heck of it, here's a quick remake of the first one in PS. Minimized but did not eliminate the magenta, need a higher-res image to do it properly.
R. |
Thanks Bear. I know, I know. Night shots should at least look like they were taken at night -- otherwise, what's the point. But this outing I was focused on camera capability, not composition -- so I didn't bother editing them, although I likely will before the week is out.
***
So, a quick recap of things to look into when I get a chance to go out again.
- tripod
- remote
- timer
- longer shutter speed to get less ISO
- a smaller aperture probably wouldn't hurt (f1.8 is a bit large for landscapes).
- composition :D
- post-process
anyone have anything else I should keep in mind?
thanks
David
|
|
|
|
01/31/2006 07:06:12 AM · #8 |
I have no idea what the lines are. Re: your list, "longer shutter speed for less ISO" isn't always the best idea ΓΆ€” your color throw from heat on the sensor will get worse the longer you expose. You'll need to compromise here. It's less of a problem with the 20D as the sensor seems to be better insulated from the heat source AND we have superior high-ISO performance.
Your tripod needs to be nice and solid, and it needs to be at a comfortable working height WITHOUT extending the center column. This latter is especially important for long exposures, were vibration can creep in from stray breezes and such. Bogen/Manfrotto 3021 Pro is a very good tripod at a not totally outrageous price, but it's still a couple of bills by the time you get a decent head on it.
As for the remake, yeah I know you just were posting some quickies for illustration; I was just bored and figured it might help other readers to see these really ARE night shots :-)
R. |
|
|
|
01/31/2006 10:28:57 AM · #9 |
I like the warm glow/surreal quality the test shots have.
In addition to all the things mentioned earlier in the thread, something that I thought I'd point out. When Bear_Music edited it, obviously, he darkened it to look more night-like. By simply dropping ISO, closing down the aperature, or increasing the shutter speed, you could produce the same result in-camera. Of course, if you decrease the time the shutter is opened, you'll loose the star trails, if they are important to you.
Basically, if you want the surreal light you have, which is kinda cool, you're on the right track. If you want it to look more nightlike, I'd experiment more with a smaller aperature and lower ISO to start (assuming you want the star trails). The closer you get it to your vision straight out the camera, the better.
Looking forward to more of these shots. :-) |
|
|
|
01/31/2006 11:33:03 AM · #10 |
Ive had success with ISO 1600 F5.6 and usually not much more that 1 minute on the shutter speed. Otherwise you will start getting the sensor heat.
|
|
|
|
01/31/2006 11:36:21 AM · #11 |
Originally posted by Gabriel:
Originally posted by David.C:
In all of them, so some degree, in the upper left hand corner there is a purple glow -- What is it? what causes it? ... and, most importantly, how do I prevent it?
|
Some 25s shots with a DSLR...Perhaps you forget to close the optical viewfinder? Light also enter there. |
The mirror flipping up closes off that light path.
The reason some SLR cameras have curtains or covers for the viewfinder is to avoid stray light from entering through the viewfinder when the mirror is down and your eye is not over it such as when the camera is on a tripod and you are using a remote. That stray light will affect the metering and lead to underexposure.
The purple glow is, as Bear stated earlier, due to heat generation inside the camera. Rather than exposing one frame for that long, it's better to make several shorter exposures and "stack" them, either in a dedicated stacking program or in PS (I think you can just stack them alll as layers and adjust the opacity of each layer to 100%/#frames, but I'm not certain). Stacking will do two things: It will reduce random noise in the final image and it will eliminate the purple glow in the corner of the image. Stacking is pretty common in astrophotography where cumulative exposure times can run into the hours.
|
|
|
|
01/31/2006 11:47:07 AM · #12 |
Originally posted by Bear_Music:
You talk about using bulb and a stopwatch; you DO have a remote release, right? If not, you have to get one; you cannot avoid camera shake in bulb mode without one.
Robt. |
You can, on cameras that have T instead of (or in addition to) B on the shutter speed settings. The difference is that with T you press the shutter button and the shutter opens. It stays open until the button is pressed again. To eliminate camera shake, you would cover the lens by holding a black card over it, open the shutter, remove the card after a few seconds (to allow the transient vibrations to settle), time the exposure, replace the card over the lens, press the shutter again.
Unfortunately, the Canon DSLRs that I know of do not have T, only B. Yet another way (in addition to not allowing a standard mechanical cable release) that Canon drives sales of their overpriced (IMO) electronic remote releases.
|
|
|
|
01/31/2006 12:52:50 PM · #13 |
| The NOAA currently has 5 Polar Orbiting Satellites in service. They orbit from pole to pole (North/South), and are visible to the naked eye.(//noaasis.noaa.gov/NOAASIS/ml/genlsatl.html) They would be my guess as to your trails. |
|
|
|
01/31/2006 01:10:47 PM · #14 |
A friend of mine has a good video tutorial on night photography on his web site - well worth a watch. Video Tutorials
The purple on your shots is caused by the sensor heating up through the exposure. Not much you can do about that short of buying a camera with better long exposure performance. I'm lucky enough to be able to shoot 2+ hour exposures without problems (haven't tried any longer than that)
Not sure about the vertical lines though - it seems doubtful that something you couldn't see would leave visible trails, in that short a period of time.
For star trails, I find ISO400 at about f4/f5.6 works really well - though that depends on the noise performance of a D70 at ISO400.
Is stray light during metering the only reason for the eyepiece covers ? I've seen problems during exposures when I've metered with my eye over the lens and shot, but with the sun shining on the back of the camera.
The 1DII manual is sufficiently vague on this topic:
'If you take a picture without looking through the viewfinder, stray light may enter the eyepiece and affect the exposure. To preveint this, turn the eyepiece shutter level as shown by the arrow...'
Message edited by author 2006-01-31 13:16:12. |
|
|
|
01/31/2006 01:13:14 PM · #15 |
Originally posted by PhotoArt:
The NOAA currently has 5 Polar Orbiting Satellites in service. They orbit from pole to pole (North/South), and are visible to the naked eye.(//noaasis.noaa.gov/NOAASIS/ml/genlsatl.html) They would be my guess as to your trails. |
Spy satellites are also put into similar orbits so that they can have coverage of the entire earth.
|
|
|
|
01/31/2006 01:16:48 PM · #16 |
My latest night image.
Shot this with my Olympus E-1 in Philadelphia at the water works.
60 seconds
ISO 100
F/22
Focal Length 19mm
WB 5050k
Noise Reduction On
I would suggest using Noise Reduction to remove the light on the top left. The lines got me too. PhotoArt said they might be satellites but if they are why do they appear in front of the clouds? Also how long was this shot? 11 minutes? I don't think all three would pass in that short of a time. The space Shuttle takes 90 minutes to circumvent the earth and that is only at 250 miles high. I am sure NOAA's birds are a little higher then that. I could be wrong. Nice theory though.
|
|
|
|
01/31/2006 01:18:48 PM · #17 |
Originally posted by MPRPRO:
The lines got me too. PhotoArt said they might be satellites but if they are why do they appear in front of the clouds? |
Was there any ambient light when you took the shot ? How about bugs flying around ? Did you have a flashlight with you ? |
|
|
|
01/31/2006 01:30:45 PM · #18 |
Originally posted by David.C:
Well, after having it for several weeks and just taking snaps around the house to get the feel of it -- I final had the chance to take my new D70 out for a real-world test drive. I've seen the night shots that have been posted in the past couple of months, and have wanted to try my hand at it -- so that is what I did. I walked up to the lake near about a mile from my house and tooks some images. This was after 11:00 pm (5+ hours after the sun had set).
I was cold so I wasn't out very long -- and these images have had no post-processing other than default raw conversion, resize and save for web. All were shot without a tripod, with the camera sitting on something. The settings for all three were ISO 800, f1.8, 25 sec.
Next time I'll take my tripod and remember to use the timer (many were spoiled by shake as I pressed the button). I'll also buy a cheap stop watch and use bulb mode to give a longer shutter speed so a lower ISO can be used. But that was the intention when I went -- to know what I needed to do next time to make it better.
The reason I'm posting them is that I have some questions on how to do this better. Here's a sample:
the questions
In all of them, so some degree, in the upper left hand corner there is a purple glow -- What is it? what causes it? ... and, most importantly, how do I prevent it?
In the last one, there are 3 vertical curved stripes (top, middle-right). This is the only image of the set they appear in. If it's important, it is the southern sky. What are they?
David
/edit: clarity |
Great pics but when I take night long exposure I want it to look more like night that daytime with stars. Bear darkened one for you and that makes it look more realistic. Try putting the ISO back to 100 or 200 and let the timers cook a little more if needed. If there is any ambient light I usually go f18-20 ISO 100-200 and let it cook for as long as needed based on lights and illumination. No expert and yours are great. COngrats, hope you work the purple haze issue.
|
|
|
|
01/31/2006 01:34:18 PM · #19 |
Here's a couple of night shots I did recently:
45 minutes, with the focus screwed up 'past' infinity :(
15 minutes
couple of minutes, mainly to get the clouds moving
Message edited by author 2006-01-31 13:34:42. |
|
|
|
01/31/2006 01:37:58 PM · #20 |
Only real available light was the bright fullmoon. 30 second exposure with f11. Used ISO 200 to minimize noise caused by long exposure. I was really happy to notice there really was none. Didn't use mirror lock as D50 doesn't support it (as far as I know9. Used "self-timer" (at 2secs) to avoid camera shake.
Oh yeah, good tripod is mandatory for this long exposures. And like somebody already said, you need a remote to really experiment with the Bulb-mode.
Hope I was helpful for once. :) |
|
|
|
01/31/2006 01:46:59 PM · #21 |
That was 800ISO f5.6 and 30 seconds.
Ive noticed with the D-70 anything over 1-2 minutes your sensor will start heating up causing the purple area on the picture.
|
|
|
|
01/31/2006 01:50:27 PM · #22 |
Originally posted by wsteyn:
Hi David - maybe some bad news. I've found exactly the same thing
About 11 minutes exposure at F8 ISO200, exactly the same glow, exactly the same place.
I noticed it on some previous shots and tried to close every hole, but it remained there.
My brother-in-law did some star-trails with his D70 over the week-end, will check with him if he's seen the same thing. |
This one has it as well:
It is only a 30s exposure, +2EV in raw conversion. And it was cold enough to cool down the camera. :)
Shot from a monopod that I pushed 60cm into the snow. Just to try this moonlit stuff out, I was there for the aurora, but there wasn't any. :(
This is unacceptable from Nikon, they should give us all a D200! :)
|
|
|
|
01/31/2006 02:03:53 PM · #23 |
Turn on long exposure noise removal. It may help.
Nick
|
|
|
|
01/31/2006 02:09:46 PM · #24 |
Originally posted by Nikolai1024:
Turn on long exposure noise removal. It may help.
Nick |
Eeek, just don't do that on a Canon camera on a _long_ exposure. The camera will shoot for twice the exposure time, once to expose, once to shoot the dark frame.
15m exposures become 30m and so on. |
|
|
|
01/31/2006 02:12:06 PM · #25 |
Originally posted by Gordon:
Originally posted by Nikolai1024:
Turn on long exposure noise removal. It may help.
Nick |
Eeek, just don't do that on a Canon camera on a _long_ exposure. The camera will shoot for twice the exposure time, once to expose, once to shoot the dark frame.
15m exposures become 30m and so on. |
So is Nikon but that should remove noise generated by the sensor.
Nick
|
|
