How does ASA setting affect a digital photograph? I know w/ 'old school' (aka film/slide) photography, the higher the ASA, the more f-stop you could get at a similiar shutter speed, and hence more depth of field. Or, you could get a faster shutter speed at the same f-stop But, that came w/ a price - film graininess increased w/ higher ASA's. So how does a higher ASA impact digital photography? I would assume since there is no film, the image doesn't get grainier (at least it doesn't seem like it does w/ my experimenting). What are the downsides to increasing ASA? Should we always use the maximum ASA settings for model photography?
Dave, It does the same as ASA in film except that graininess translates to digital noise. What is digital noise? A good example is in the dark areas of a photo, you get some off colored pixels that are not quite black or dark. The higher the ASA in a digital camera the more of these pixel noises that you will see. Digital is no different than film, don't use an ASA higher than what you need to.
I've doodled in Photography on and off most of my life. Owned a couple of Canon SLR's still own one, the old F1. I now also own the Nikon 5700, wish I waited until the 8 meg came out. but thats the way it worked out. ASA relates in laymans terms to films sensitivity and speed to light. Like mentioned above the higher the ASA the more speed the film can handle, its the same in the case of Digital Cameras. Only its not film, its in a program that affects light sensitivity of the CCDs or whatevers being used in the camera. In the digital lets believe you have the camera set to 1/60 second shutter and a f stop of 22. Crank up the ASA and the camera will recieve more light more quickly at the higher ASA settings. This is without changing the shutter or F stops. Lower it and the reverse will happen. What speed means/sensitivity of film or in your case digital settings is that lower light levels can be used on Higher ASA films. Its also good for action shots of which higher shutter speeds are often used to capture the action. So to clarify, the more sensitive the film (or higher the ASA) the faster the film is, and you have more freedom to use higher shutter speeds and or shoot pics in lower light levels. There are tradeoffs for the high speed or sensitivity, graininess is one of them, color shifts, I don't recall all of them but those are the major ones to be concerned about. For modeling purposes, close in photos are the rule rather than the exception., so you want a lot of intense light, (careful not to melt the models with the radant heat) you also want a good depth of field (high F stop) preferrably over F22. then crank the shutter to match the meter reading with the light source available. This takes experimenting with. Often the most difficult shots are those from train meets or shows, where you cannot control the light source of intensity, and you might have multiple sources of light with different spectrum bulbs, which further complicates the results. MK's example of noise in digital is good, as oversaturation of light (in relation to the rest of the photo) on the pixels translates to noise or bright spots on digital camera prints. If your interested in model photography use the lowest asa (around 60) on your camera. Use the highest F stop the camera has to increase or maximize depth of field, and then adjust the shutter speed to accommadate those settings with the light source. If you cant get a solution on the camera for settings, either one of a few things can be changed, First increase the lighting, or increase the ASA, or use a timed shutter (camera mounted on tripod) Keep in mind that changing the latter two of the above affects coloration. Rob
Rob, Great post! This covers it far more comprehensively that I ever could have. I might add that some digital cameras seem to handle high ASAs (or ISOs) than others.
Pete, that's correct. If you want the ultimate in high ASA and low noise, check out a digital SLR. I've shot ASA 400 on my Nikon Coolpix 950 (ancient) and you can see the noise. I've tried ASA 1600 on my Nikon D70 (digital SLR) (Hearst Castle - no flash photography allowed) and you better have a good pair of glasses to find the noise! The Canon DSLRs are even better as they use CMOS sensors instead of CCD.
Credit where credit is due- all of these answers were most informative and concise. Thanks for sharing.
In Alaska, my "Moose at Midnight" photo was shot on a D100 at ASA 1600. There was only a little degradation, but no noise. I often use 400 or 800 for wildlife photography with a telephoto--it gives me a higher shutter speed. I now have a D70 body on order. For model photography, I'd suggest using the lowest ASA, and the "finest" (largest) resolution. You'll probably still need a good tripod. I'm still trying to master multiple flashes--this really isn't my bag. I'll admit that I have no experience with the new high megapixel (8 mpixel) consumer digital cameras. They seem to have good macro capabilities.
