Tuesday, March 22, 2016


Digital cameras have freed us in many ways—not the least of which is choice in ISO.  As a professional photographer in the film era it was very frustrating being tied to a film type once it was loaded—especially 35mm, where if you had to change film mid-roll you had to rewind it back into it’s canister without loosing the leader, etc. 

When I went fully professional, using only medium format cameras, at least we could change film backs at will for more film/ISO choices.  Of course, you had to invest (at $400 to $500 each) in 4 or 5 film backs pre-loaded with the film you thought you would need for each job.  In addition we bought our pro-film in bulk that had to be refrigerated and couldn’t be loaded into our cameras until it was acclimated to room temperature—so, film usage took planning.  Those were the “Good Old Days”…I do not miss those days!

Where I really like this ISO flexibility is when I’m walking around in a low light environment, without a tripod—I hate lugging a tripod, especially on vacation! So, because I’m usually hand-holding my camera, regardless of my lens choice, my ISO starting point is 400. I’ve never been fond of any of my DSLR’s “native” ISOs—I’ve always regarded 100 ISO pretty much useless.  Nothing new here; in all my professional years using medium format film my starting point was….ISO 400 films and then the advanced 800 films supplemented by 1600 and 3200 Black & White (loved T-Max 3200 especially pushed to 6400!) films. 

The following images show three different camera generations at higher and higher ISOs….
f2.8 @ 0.3 sec., ISO 800 ~ Camera Fuji Pro S-2 (2003)
You want low light try a cave!  This was taken in the Cavernas Chaaktun at Playa de Carmen in Quintana Roo, Mexico.  With the lens wide open at f2.8 I went to 800 ISO ( 1600 was pretty noisy back then ) to keep my shutter speed to a controllable .3 seconds, where I could rest the camera on a safety railing.  Love that crystal clear water and reflections!

Next we skip a camera generation where I’m walking through the Idaho State Fair at 8:30pm ( right at sunset ) when I spot this antique farm pump.  It’s whirring, popping and hissing along with a dozen other steam powered farm machinery that stops me in my tracks.

f5.0 @ 1/30 sec., ISO 1600 ~ Camera Fuji Pro S5 (2010)
I picked f5.0 to give me the depth-of-field I needed to see what’s behind the spinning flywheel—I’m in pretty close, so my depth-of-field is shallow.  I only need 1/30th sec., (it’s an easy hand held shutter speed) to blur the flywheel; if I went any slower the flywheel would be too clear loosing its sense of motion—and 1600 ISO got me there.

Key Point:  In the digital age we use ISO as a tool to achieve the f-stop and shutter speed we require to tell the story.

Five years later I’m back at my Idaho State Fair, this time using a quantum leap in camera development over my previous DLSRs—the Canon 5D MKII.

f5.0 @ 1/100 sec., ISO 3200 ~ Camera Canon 5D MKII (2015)
Again, I pick my variables and use my ISO to get me there. With my lens at 24mm I pick f5.0 for good depth-of-field. I picked 1/100 sec., (with some testing) because that shutter speed will stop the spinning ride’s red wheel, but let the people’s motion blur a little.

Technical Note:  The ISO “sensitivity” settings on your DSLR are NOT analogous to film speed or sensitivity.  Despite what you see on the internet or forums your DSLR camera sensor’s sensitivity is FIXED—it is NOT variable.

Raising the ISO number on your digital camera merely underexposes the image. Then, post-exposure, gain is applied to the signal, from the sensor, proportionate to how many stops you have under-exposed the image. Unfortunately, the gain applied to boost the signal also boosts noise, especially in the darkest (most underexposed) regions. That’s why it’s better to slightly over-expose a low light/high ISO image than to under-expose it. 

I’ve been using the ETTR ( Expose to the Right ) maxim for 15 years; I encourage you to do the same.

As usual, should you have comments or questions please don’t hesitate…’Til next week…

Author: Jerry W. Venz, PPA Master Photographer, Craftsman, Certified
Training site: http://www.LightAtTheEdge.com

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