Sunday, November 29, 2009

Part 2: Photography with Imre Z. Balint: Episode 3 – Sensitivity

The topic of sensitivity in itself is quite simple to understand and demonstrate, but gets much more involved when tying it together with aperture and shutter speed to achieve the image you want. With a little practice though, it’s not that hard to master... or at the least, become proficient at getting the right settings.

When I was editing my video, I wish I would have left a section in that discussed some ISO settings for varying lighting conditions and how I generally evaluate a scene when I take photos. So at the least here is the written version (although I may just make a video addendum to episode 3 later).

General ISO Setting Guidelines
In regard to setting the sensitivity of my camera, I usually base it on the amount of available light and use the smallest ISO value I can for that situation:

ISO 100 – For lots of light, usually outdoor shooting on sunny days
ISO 200 – For outdoor shooting on cloudy days
ISO 400 – Bright indoor conditions
ISO 800 and up – Dark indoor conditions or night shooting / astro-photography

Now I want to really emphasize that the above should only be considered a general guideline, and because photography can be both an art form and require bending of the rules to get what you want, you may likely disagree with the above... frankly so do I. For example, when I shoot longer exposure images (e.g. star trails or aurora), I prefer to use ISO 100 to reduce the amount of noise in the image. But some photographers may like to get crisper details in their aurora photos and use 1600 or 3200 ISO instead to increase the shutter speed.

This also does not take in account if you’re using a flash. When I work in my studio, although usually a dark place, there is an ample amount of light when the strobes go off. So in that case, I’m back to ISO 100.

Aperture can also affect what ISO setting you may need. I enjoy macro photography, but when you get close to tiny subjects (like insects), the depth-of-field (DOF) also decreases. So I up my f-number to something around F8 or F10 (to increase DOF)... but that of course restricts the amount of light passing through the lens. Therefore, even if it’s a sunny day, my shutter speed may become too low for me to hand-hold my camera without getting a blurry image. To compensate, I raise the ISO value higher to get a shorter exposure.

Steps to Consider Before Taking a Photo
This brings me to how I evaluate a scene before I take a photo. Again, this is just a general guideline, but a good starting place if you’re new to photography. And I want to highlight that I most commonly use the Aperture Priority (that “A”) setting when taking pictures; the steps below assume that.
  1. First I begin by evaluating how much light is available... in other words, I look around.
  2. Based on my observation, I set my ISO to a level where I believe I’ll get a decent shutter speed and the least amount of digital noise in the image.
  3. I set my aperture to my liking. At this point, I check what my shutter speed is, because as mentioned earlier, the aperture setting could force me to either open wider or turn up the ISO. In addition, I often set my aperture before setting my ISO, so again, this is where you’ll likely end up forming your own style when taking photos.
  4. Yup, I take my shot.
Although these few steps are at a basic level and don’t include such things as special needs (e.g. tripod, flash, etc.) or composition, it’s an easy place you can start.

Links to Sites on this Topic:
And now for some useful website links that detail camera sensitivity and digital noise:
http://www.iso.org - The standards organization
http://en.wikipedia.org/wiki/International_Organization_for_Standardization - Wiki on the standards body
http://www.photoxels.com/tutorial_iso.html - About the ISO setting
http://www.dpreview.com/learn/?/key=sensitivity - About ISO on dpreview.com
http://en.wikipedia.org/wiki/Film_speed - About film speed
http://en.wikipedia.org/wiki/Image_noise - Wiki on image noise
http://www.photoxels.com/tutorial_noise.html - About sensor noise

No comments:

Post a Comment

You may comment, but if it's spam or advertising, I'll be deleting your comment and blocking your arse!