Splotchy skies
I am a fledgling to photography and I've a nikon D80 kit which includes the 18 - 55mm AF-S II lens. While I am for the most part satisfied with the photos I've been getting, I've noticed a problem with blue skies/night skies. When viewed at 100% the blue field is splotchy and grainy. This happens while shooting in auto or program mode cloudy, shade, sunny... whatever. Any suggestions on this issue would be greatly appreciated.
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-Fleetwood Mac
Large Jpeg! I've been wary of RAW images because of my ignorance in post processing photos. Another alligator to tackle, but well worth the effort for great shots! I know there's some lurking out there for me.
Thanks for your response!
It is best to avoid using the Auto modes, as they may allow the camera to set your ISO higher than might be preferable and this will contribute to noise and jpg artifacts.
Shooting in Manual or Av or Tv is generally a better plan.
Viewing images at 100% on a computer monitor can be entertaining, but does not necessarily mean that the artifacts you can see will be visible in a print at a normal viewing distance.
Moderator of the Technique Forum and Finishing School on Dgrin
Don't be affraid of RAW! I used to be wary of it, but now, i'm getting really POed is somehow my camera changes settings withought me knowit it.....
Anyway, you need to get into habbit, and just leave it in RAW at all times. You'll be pleasantly surprised! And PP is a lot of fun, you really get to know your images, and can compare before and after shots. Why would you want to miss that?? I know time might be an issue here, but ones you pop, you can't stop. Every time i shoot, i can't wait to start PPing
Auto mode, just forget about it. I shoot strictly manual, 100% It gives you so much more control, you'd be surprised what you can do. Good luck, keep shooting and learning, it's addicting!
www.intruecolors.com
Nikon D700 x2/D300
Nikon 70-200 2.8/50 1.8/85 1.8/14.24 2.8
The advice given by the others is good. I'm going to amplify somewhat, repeating some of the earlier advice for completeness.
The major change you need to make is to dispense with auto-exposure and handle your exposure settings manually. Just set your camera's exposure mode to "manual".
For night sky shooting, the biggest problem you have is lack of light. Your auto-exposure compensates for this problem in a number of ways. It does this sometimes in a "not so logical" manner. The basic concept is to take manual control of these exposure subfunctions, so you can minimize artifacts in your picture. After setting your camera's exposure mode to manual, compose and focus your shot, and then set your aperture to 1-2 EV stops below the widest setting available for the zoom length you are going to use. The idea here is let in the maximium possible amount of light, without causing color fringing (at the widest aperture, unless you are using very high end lenses, a prism effect will manifest that misregisters the primary colors, causing color banding around high contrast edges). Don't worry about DOF; you are focusing on infinity, so opening way up on the aperture will cause no problem. Next set your ISO to 100 (temporarily at least, to minimize grain). Finally, meter the shot and set your shutter speed. You will almost certainly arrive at a very long shutter speed (10 seconds or more), which will cause the "splotchiness" you reported (your sensor's photocells are overheating). Boost ISO in small increments (say, 1/3 EV) and remeter as you go to arrive at faster shutter speeds. The idea is to arrive at an optimal combination of ISO and shutter speed. What's "optimal" depends on your camera, since camera's differ in their relative ability to handle high ISO artifacts ("luminance noise") and slow shutter artifacts ("chromatic noise"). But, as a generality for low light situations, try to get ISO under 300, and shutter speed no more than 3-5 seconds. This strategy will reduce, but definitely not eliminate, the grain and splotchiness. You'll need to learn some Photoshop techniques to address the remaining artifacts (these techniques will soften the image, requiring extra sharpening toward the tail end of post-processing). Finally, shoot in RAW, TIFF, or highest quality JPG mode (this will prevent JPG artifacts).
Regarding having the same issues with daytime blue skies, the underlying cause of the probelm, and strategy to remediate, are likely the same. Although lack of light is not a problem here, you still have the issue that your camera's auto-expsoure may not be selecting an optimal mix of shutter speed, aperture, and ISO to minimize artifacts (e.g., if your camera is more sensitiive to ISO noise than chromatic noise, the algorithm should aim for lower ISO at the expense of a faster shutter speed, but it may not be doing this). Using the night time strategy above will work here, but with even better results. You will most likely be able to leave your ISO at 100, and still have a fast shutter speed (hopefully under 1/60 second). This will likely leave your image artifact free, requiring little or no post-processing in Photoshop.
No doubt much of the above is cryptic. I would advise that you get a good book about how to set exposure, or do a Google search on phrases like "setting camera exposure manual mode". Then, come back and reread the two paragraphs above.
Finally, full Photoshop CS3 is expensive and has a long learning curve. You might want to start out with Photoshop Elements (about $100), which is geared specifically to digital picture workflow (will cost about $500 less than PS CS3, and will be much easier to learn).
Hope the above helps.
Best regards, Stu