This is an article written for PSRI about cleaning the sensor of your camera.
Wednesday, February 17, 2016
Monday, February 15, 2016
Admit it! A lot of you are afraid to shoot the stars at night: afraid of mistakes, blurring, messing up the images somehow. Well, I am here to help you succeed with a few simple tips that will get you on the right track: good images right from the start. It isn't hard at all but you must follow my formula at first, then you can feel free to try other options after you get some experience.
First, there are some important things to remember about night photography: cameras and lenses.
- A full frame DSLR will give the best results. Why? Because the pixels are larger, therefore more photons are absorbed and less noise is visible. If you have a mirrorless or APS-C sensor, try it and see if the noise can be controlled.
- A fast wide angle lens. Glass is god at night...if you have a cheap lens forget night photography, so invest in one good quality wide-angle lens if you are serious about night photography. I usually use a Canon 15mm F2.8 fisheye because it can give 180 degrees of view: more sky is better in night photography; my other lens is the Canon F 2.8 24-70mm. You can use an F4 lens: I have used the Canon 17-40mm. All these images were taken with one or the other of those two lenses. Fisheyes can be amazing at night; I correct the perspective in PS and noise in ACR (adobe camera raw).
- Sturdy tripod with ballhead: I have a Gitzo that is over 10 years old with a reallyrightstuff ballhead. This stuff is kind of expensive but there are loads of other options out there.
- To shoot star points you don't need a cable release unless you think it looks cool.
Ok, now that we have our equipment ready. What next? Get your night infinity setting! During the day, you are going to go into "live view" on your camera, make sure you have the wide angle lens attached and set the widest F-stop you have: F1.4, F2.8, or F4 with the camera on Aperture Priority. ISO isn't important for this part, whatever works for you; let the camera choose shutter speed. Put your lens on "manual"(MF) not automatic: this is to get the infinity setting you will need. Point the camera at an object about thirty feet away and set the live view to 10x : there is usually a button to enlarge the live view image. While in this mode, focus with the focus ring manually until that object is absolutely sharp, then review the image for sharpness: if it is sharp, look at the setting on the distance scale, it is usually just short of the infinity mark; the infinity mark is not a good place to put the lens as it keeps searching for infinity. You will find that the sharpest point will be perhaps a quarter or half inch left of the infinity mark. Memorize this spot! If you can't remember this spot on one lens, tape it with an easily removable tape. Do this procedure in daylight or you will go crazy at night.
Now you are ready to go!
The Milky Way is pretty weak in the Northern Hemisphere between December and February. It is more vivid in summer...the featured image of the light painted rocks at Arches was taken in January; the Milky Way is visible but faint. The following image was taken in Rhode Island, at a beach, in the middle of summer. Notice the difference.
Ok, now you are excited to go: grab the camera, tripod and put the lens on the camera. Make sure you do the following things:
- Put the camera and lens on manual. Be certain to shoot in RAW.
- Set the distance scale on the lens to the infinity setting you figured out during the day.
- Set the aperture for the fastest F-stop on your lens. It is 2.8 for me.
- Now, this is important, so pay attention: If your widest aperture is 1.8, use an ISO of 1600, if it is 2.8 use an ISO of 3200, if it is an F4, use 6400. These are good starting points, and may need adjustment up or down depending on results.
- I usually use Auto White Balance and by shooting in RAW, you can adjust the color of the image in PS.
- What about exposure length? Now comes the math part, but you can do this! The most important number is 500 for night photography (some people use the number 400) OK, what is this 500 thing?
Here is how it works: Your exposure is your focal length multiplied by seconds but less than 500. simple isn't it? If your focal length multiplied by time in seconds exceeds 500, you will not have star points, but star blurs or short trails and it looks like hell. Another important point: don't let your seconds ever exceed 30 since the Earth is rotating and the rotation will be obvious in stars at a greater than 30 second exposure. You want to get as close to 30 seconds to allow more light into the camera, but not exceed it. Sounds complicated but it isn't: here are a couple of examples: my F 2.8 lens is 15mm and I want to get as close to or at 30 seconds but not exceed it or the 500 point:
15 x 30= 450 so that keeps my exposure under 500 and not above 30 seconds...
So my camera setting would be: F2.8, ISO 3200, 30 seconds (at the infinity setting) with an Auto White balance.
If I had a F4 and 24mm lens: 24 x 25 seconds would give me 600, which is too high...so I reduce it to a 20 second exposure and it gives me 24 x 20=480. There is the best setting: F4, 20 seconds, ISO 3200, (preset infinity setting), and AWB.
Look at each image and make sure it is clear: x10 on the LCD. If the image is too dark, go up to the next ISO..If 3200 is not giving enough light, use 6400...I personally don't use long exposure noise reduction as it doubles the exposure while it shoots a dark frame.
Another important item: I always bring a strong flashlight to light something of interest in the foreground...it will improve your night images if there is some foreground element of interest. This is when you can practice a little light painting. If you don't want to light paint, shoot the foreground before dark, then combine it with the night sky image taken much later in the same spot.
Shoot away from light pollution on crystal clear nights with little moisture in the air. Also, there are apps for your smartphone that can help locate the Milky Way for you: I use Stellarium, but there are others: StarWalk and SkySafari.
Practice will make your images amazing...be sure to dress warm while shooting at night or you will get cold and cranky and as everyone knows: multiplying cold x cranky= bad images.