I have two tips that I consider to be the most useful:
(1) Get the shot regardless of ISO, and deal with the noise later
Shutter speed and aperture are both essential technical and creative elements in capturing a subject or scene in the way you intended. If the shutter is too slow, you can't freeze a subject's movement or control the amount of motion blur, and you may risk camera-shake-induced blur into the bargain. If the aperture is too wide, you may lose the required depth of field to keep certain areas of your image sharp enough, or you might find the lens is operating outside its optimal performance limits (especially wide open). All too often, we photographers reduce our shutter speed or open up the aperture to let in more light, allowing us to keep the ISO low and avoid noise, but this is at the expense of our creative control over the captured image. My tip is to shoot with the optimal shutter speed and aperture relative to your subject and the effect you are trying to achieve, and accept whatever ISO is necessary to support that. Noise reduction facilities in freeware and paid applications (GIMP, Photoshop, Lightroom and Pentax's own Digital Camera Utility) have improved so much over the years; we can now shoot confidently at ISO 6400 or higher and achieve fantastic, low-noise results with just a tiny amount of post-processing (I have captured useable images right up to the K3's limit of ISO 51200). My point is, it is better to get the shot you wanted and have to deal with some noise (which can easily be remedied), than to compromise your creative control over that shot. Either shoot in TAv mode, setting the shutter speed and aperture as required and letting the camera decide on ISO, or shoot in M mode, setting the shutter speed and aperture *first*, then adjusting the ISO to obtain the correct exposure.
(2) Stop pixel-peeping!
We digital photographers have become obsessed with sharpness, detail and noise in our images. We view and edit our images at 100% reproduction on our high resolution computer monitors, and agonise over the slightest imperfections. But this isn't how others view our images, and it's not how we would look at someone else's images either. My tip is to stop pixel-peeping and accept that the equipment we use, and our techniques, have limitations. Many of our captured images will have numerous imperfections, but what's important is how the images look overall when viewed at a realistic size, from a realistic distance. If a photo looks good viewed at full-screen size from a couple of feet away, it really doesn't matter what you can see when viewing it in your image editor at 100%. If an image looks good at a realistic size, viewed from a realistic distance, it's a GOOD image, and it doesn't need another hour of effort in post-processing. Once you start to appreciate your images in this way, you'll get much greater enjoyment from your photography and the equipment you use.
Last edited by BigMackCam; 01-16-2016 at 07:58 AM.