AboutScott Valentine Expertise Most anything about digital post processing (Photoshop, etc), effects, and image restoration, some technical information about digital imaging systems, light and electron microscopy, optical physics and image analysis. I can help with shooting basics, lighting setups, and getting the most out of your digital camera. I am also an 'expert' here for Photoshop (Computers/Technology > Software > Graphics Software > Photoshop).
I am currently writing a book for Adobe Press on composite artwork using Photoshop CS4.
Experience I've been an image analyst and advanced amateur photographer for over 6 years. I run an Adobe user group, focusing on digital media, and have lectured on digital image capture systems. Currently, I am an administrator for a rather large instructional Photoshop forum
Organizations Adobe User Groups, National Association of Photoshop Professionals, Advanced Imaging Specialists
Education/Credentials Bachelor of Physics, University of California, San Diego
Awards and Honors Winner: Best in Show and several category first place awards - Imaging Professionals of the Southwest Print Competition (multiple years)
Expert: Scott Valentine Date: 1/13/2007 Subject: ISO and Shutter Speed
Question Hello again,
Thanks for you very informative answer! I was wondering what my best bet is for taking low light shots of non illuminating objects (like people).
Also, in what situations would you use something called a Flash Exposure lock?
Thanks,
David
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The text above is a follow-up to ...
-----Question-----
I heard that film speed and shutter speed both play a role in photography especially when dealing with low light shots. They both seem to do the same thing; how would you adjust them accordingly for quality shots? I have a canon powershot sd600.
thanks!
-----Answer-----
Hi David,
Both 'speed' values deal with light versus time. In the case of film speed (ISO), it is a measure of how sensitive the film is to light, or the gain on a digital sensor. The more sensitive a film or sensor is to light, the less time it needs to be exposed, and the less total light needs to be available.
Unfortunately, that also means lots of noise in your image.
Shutter speed is perhaps more obvious, and controls how long your film or sensor is exposed. This has an impact not only on how bright your image is, but whether motion is stopped or blurred.
Combining the two is like fine-tuning your shot. Careful choices must be made when attempting a specific look or effect. With two 'perfect' exposures (meaning, exactly the right amount of light hit the sensor), one may show completely frozen motion of horses running, the other may have some nice, soft edges like flowing water. The point, then, is to try and visualize what image you want to end up with, and adjust accordingly.
The other component is 'speed' of your lens, or how wide the aperture is in relation to the length. Aperture is the opening of your lens closest to the sensor, and defines depth of field. Depth of field refers to the relationship between blur and distance in an image, typically centering on the theoretical focus distance. Portraits shot with a wide aperture have low depth of field to make the subject stand out from the background - the subject is in focus, while the background is blurred. Landscapes on the other hand typically use small apertures to take in more of the scenery.
The aperture size also limits the amount of available light, so combines with ISO and shutter speed to control the effect on your image.
I highly recommend just playing around with various settings, and perhaps taking a short photography course to learn more about what goes on in an image. Keep notes on what settings you use, even if you are using programs, and how those settings relate to the look in your image.
Keep in mind that higher ISO settings typically mean more noise, while lower settings require longer exposures. Since many digital cameras now include ISO selection, we are able to have that much more control over our images. Lots of choices is a good thing!
I hope this helps. If you have other questions, please let me know.
-Scott
Answer Honestly, the best thing you can do is throw more light on the subject. I know that's not always possible, so here are some tricks that might work for you...
*Above all else, use a tripod! Get one that is rated higher than your camera weight, and if possible, one that has a quick release plate for the bottom of your camera. This makes things much easier when switching between handheld and tripod shots. If your camera supports it, also get a remote release cable, either mechanical or electronic, depending your setup and cost considerations.
*Carry an incadescent flashlight (as opposed to LED). This will allow you to 'paint' your subject during long exposures. If your camera's shutter stays open for more than a second or two, this is a great way to reduce noise and possible add some character to your shots. Just click the shutter, and wave the flashlight at your subject. This takes some practice, but can be a great way to get tough shots.
*Flash! It's an obvious choice, but not always the best solution. Canon's done a great job with onboard flash, but it's good to have alternatives :)
*Reflectors can be made from auto sunshades, CDs, or virtually any other reflecting surface you can get your hands on. Sometimes this is the only way to get more light where you need it, so look around for whatever might be available.
A flash exposure lock is something you use to finely control your lighting. The idea is to take some exposures to choose the best lighting from the flash, then lock in those settings while you compose your shot. This is very helpful in situations where you know something is about to happen, but don't want to leave things to chance with full-auto settings.
