Hints & Tips


George Theodore, February 27, 2017

ISO Refers to the Sensitivity of Your Camera’s Sensor. Not!

Here’s yet another myth that belongs in the dustbin along with “you get more reach with a lens on an APS-C sensor than with a full-frame sensor”.

ISO in our digital cameras is not the same as ISO in film. Film is produced for a particular sensitivity to light and you can't change that sensitivity midstream through a roll of film. In our digital cameras, we can choose whatever ISO we want whenever we want. But, it has nothing to do with sensitivity. In fact, ISO “happens” after the shutter closes.

Here’s the way it works.

  • We increase ISO
  • The light falling on the sensor is reduced
  • We activate the shutter capturing an underexposed image
  • Shutter closes 
  • The signal from the sensor is amplified to achieve the desired brightness.

That’s it.

Because ISO is applied after exposure, some opine that ISO, therefore, has nothing to do with exposure. Well, perhaps not the same way it did with film but ISO settings do influence how much light falls on the sensor so maybe we can say it affects exposure indirectly.

So, where does noise come in? When the exposure contains fewer photons (underexposure) any noise generated becomes a larger component of the sensor’s final output signal. When that signal is amplified, both “good” and noisy parts of that signal are amplified. The total signal divided by the noisy part is what we refer to “signal to noise ratio (SNR)”. When the image is underexposed, the SNR is low which means we see more noise.

Therefore, there are more artifacts present in a higher ISO image. And, those artifacts are nothing like the grain we saw in high ISO film. Grain was kind of interesting; artifacts are just plain ugly. So, as we always tell our workshop participants: “Shoot at the lowest ISO required”. Of course, we’ll accept noise if that’s the only way we can capture a particular image.

Now, when you hear someone say “ISO changes the sensitivity of the sensor” you can, with confidence, say “no it doesn’t”. Some say, ISO “affects the camera’s sensitivity to light”. That’s not right either. ISO is all about simple amplification or “gain”. It's like turning up the volume on your TV.


Back-Button Focus

George Theodore, January 9, 2017

I’ve used Back Button Focusing (BBF) for a very long time. And my reasons are simple: (a) it locks focus, (b) the shutter button now has but one function – shutter release, (c) after achieving focus with BBF, I can touch up my focus manually if I choose, (d) it allows me to move around a little – I can even move my tripod – and as long as the distance between me and my focal point remains constant there’s no need to refocus and (e) if something crosses between me and my subject, my focus won’t change.

But, the one thing BBF will not do is guarantee a sharp image and I have enough not-so-sharp pictures to prove it.  There was a recent post (I forgotten where) that stated BBF improves image sharpness – nonsense.  You want a sharp image? Use good technique – tripod, solid surface, use of shutter release cable or other remote triggers or hand hold properly and at appropriate shutter speeds (for you). BBF has absolutely nothing to do with getting the image sharp. All it does is separate the functions of shutter and focus.

I also use BBF for wildlife – but the faster or more erratic the movement, the tougher it is to use. For example, I sometimes find it difficult to track birds-in-flight with BBF but that’s just me.  In these situations, I’ll often revert to using the shutter release button to assist focusing.

I find more and more photographers using BBF. If you haven’t tried it, you should consider the benefits and give it a whirl. Cameras differ in how you set up BBF but it's basically using your AF-ON button to focus and defeating the focus function of your shutter button. Consult your owner's manual.

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The Tripod

George Theodore, May 1, 2016

Three years back, Tom wrote an article about Tripods which we carried on this site and which you can still read. This is a reminder of some of what Tom said in his piece and a result of lots of observation at our events.

With the advent of Image Stabilization, Vibration Resistance or whatever each manufacturer calls it’s “shake-proof” lenses, we see way too many photographers shunning tripods for landscape shooting and doing a lot of hand-holding. Let’s state a fact: if you want to maximize sharpness, if you want a “tack-sharp” image, if you want the cleanest image with the lowest possible noise, nothing will give you those results better than a solid platform - which your hands aren’t. As a side benfit, tripods slow the image-making process down; we take more time to look, to lhink and to compose - and that's a good thing. Finally, as we all know, a tripod is an absolute "must" for long exposures or for any type of blended imagery.

So, let’s talk about tripods: In a photographer’s lifetime, one may go through several camera bodies and lenses and even change manufacturers. The one piece of equipment that should rarely be changed is the tripod - if one makes the right choice(s) to begin with. Many new to photography know “I should have a tripod” and buy what is usually an inexpensive skinny, flimsy, light tripod. Now, one might be fortunate enough to attend an ANPW event and really learn about buying a tripod and make corrections. Others (the “unwashed”) may go through several tripods, spending a lot of money before “seeing the light”. A good tripod isn’t cheap. Neither is going through several tripods until you make a “good” choice. So, spend $1000 now or make several purchases that total $1000 or more.

What are the criteria for selecting a tripod? First, we should buy something that’s going to last. So that means solid and durable. Second (for the sake of our backs and necks) we select a tripod that, with camera mounted, places the camera eyepiece close to eye level. Third, the tripod must be capable of handling the largest load we anticipate placing on it. When calculating that load use your heaviest anticipated camera-lens combination plus the weight of the tripod head. Don’t have that big glass but thinking about a purchase soon? Consider its weight in your calculation. But, don’t forget that your tripod head also has a load rating. As a guide, Really Right Stuff uses camera-lens combination examples to help in deciding on a tripod head.

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Time-Lapse Photography

From a Digital Photo magazine article by Tom Bol, January 28, 2015

If you’ve recently gone to the movies, watched TV or surfed YouTube videos, chances are good you’ve seen some time-lapse photography.  Time-lapse photography is all the rage right now.  Feature films and documentaries have long used time-lapse photography to wow viewers.  Remember watching the flower grow from seedling to mature plant in mere seconds, or watching the stars rotate in the night sky over a jagged Himalayan peak?  Time-lapse photography was once a complex process reserved for high-end productions, but not anymore.  Today this dazzling technique is available for any photographer, and it’s never been easier.  Some DSLRs even create the movie in camera.  Time to get out and shoot some time-lapse!

How it works.  Time-lapse photography involves shooting a large number of frames over a long period of time, and then merging them into a movie.  Two hours of shooting time and hundreds of frames can be merged into a 10 second movie clip, in essence speeding up time from hours to seconds.  On the extreme end, some time-lapse photography involves shooting over the course of weeks and months, and then merging the sequence into a few brief minutes of footage.

The possibilities are very exciting.  Imagine watching your next two-hour photo shoot from start to finish in a 20 or 30 second movie or seeing the transformation of light from a rosy sunset to a starry night in 30 seconds of video.  See some interesting clouds passing overhead?  Some of the best time-lapse sequences record passing storms and interesting clouds streaking through the sky. You can also combine several time-lapse sequences into a longer video.

To shoot time-lapse, we need an intervalometer. This device simply counts intervals. For photography, there are two popular options for intervalometers - either in-camera or an intervalometer cable release.  Camera manufacturers took note of the popularity of time-lapse photography, and a number of cameras have intervalometers built right into the camera. All one need do is set up the sequence and hit the shutter button.  Some cameras take this a step further, and offer a time-lapse movie option where the camera actually creates the final movie once the sequence is complete.

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Infrared Photography

George Theodore, March 3, 2014

With the ability to convert digital cameras for infrared photography, this art form is enjoying an upsurge in popularity. As photographers upgrade their DSLR’s, many are having their older cameras converted rather than “giving them away” at eBay or Craig’s List especially if that older camera is more than two or three generations old. The conversion replaces the sensor’s low pass filter with one that essentially blocks visible light and passes infrared.

The advantage of conversion over the use of infrared filters is that filters require much longer exposure times. With a converted camera, one shoots at whatever aperture, shutter speed and ISO is required to capture the image.

A few years back, I had Life Pixel convert a Nikon D200. I usually carry two DSLR’s in the field and the D200 made it three. For many trips, that’s a bit much so I had a Canon G11 converted. Finally, I had a Fuji X-E1 converted and that's now my go-to IR camera. With a mirrorless camera you don't have to be concerned about lens focus adjustments (a subject I won't discuss here). Life Pixel came highly recommended and my experience with them has been excellent. In both conversions I opted for their Super Color IR filter. I like false color IR’s (though I do some black & white too) and this filter looked like it was my best choice.

The problem most have is how to post-process the image and the biggest issue lies in proper white balance. To start, set your white balance in-camera according to the filter type; some filters do better with green (just use grass or some other foliage), others with a gray or white card. Fill your frame with the appropriate color making sure it’s in the same light you’ll be shooting, take the picture and use that frame to set your custom white balance. Your camera’s owner’s manual will tell you how to do that. Now go shoot.

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