Hints & Tips

ISO

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.

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.

Be conservative; a general recommendation is that the tripod load rating should be three times the weight that you impose on it. So, if your load of camera, lens and head equals 12 pounds, you’re looking at a tripod capable of handling at least 36 pounds.

How about center posts? A center post limits how close we can get to ground level and raising the post makes the tripod unstable especially in wind. And, in most small tripods one is limited to around 8 pounds of gear plus head combo. But, I understand that smaller tripods can make air travel easier because they fit in checked luggage so nicely and most small tripods do have center posts. If you’re considering a center-post tripod, we recommend you not have to raise the post more than two inches to get the camera eyepiece to your eye level.

But wait, if you would rather not have the center post at all, there are other options. With today’s technology - and for just a little more money – slightly heavier and more stable tripods that collapse to lengths that won’t challenge your luggage are available so look around. For example, Really Right Stuff Series 2 tripods have a load rating of 40 pounds and they’re available in three and four leg configurations. Likewise the 50 pound rated Series 3 also comes in three and four leg options. The four-leg models collapse to very transportable lengths although, depending on the length of the luggage, you may have to remove the head. I often travel with the Series 2 or 3 with the head removed.

In the past, all the above meant “heavy”. Today, with materials like carbon fiber and basalt, we have tripods that satisfy our needs for support and stability and are easy to carry as well. On the flip side, they’re expensive. But, do it right and it may be the last tripod you buy or, at least, one you’ll have for a very long time.

Which tripod manufacturers and features do we like? Both Tom and I have tripods by Really Right Stuff. We have both owned Gitzo’s, and liked them. We find, however, that RRS tripods have a slightly thicker wall and are, pound for pound and dollar for dollar, a better choice. We prefer twist locks to lever locks and do like the ability to get really low to the ground. For casual hiking – especially longer distances - we might choose a center-post tripod but our go-to tripods are either RRS Series 2 or 3.

Questions? Shoot me an email at george@amnaph.com

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.

Shooting the sequence. Once you have the gear needed, its time to shoot your time-lapse sequence. Start simple; don’t go for the three-hour sunset to stars sequence over El Capitan on your first attempt. Better to try a midday shot of passing cumulus clouds over your house.

The first consideration is exposure mode. It might sound logical to use an automatic mode like aperture priority to adjust for any differences in exposure during the time-lapse. But this can cause a lot of headaches when you seam all the frames together after the shot. Flicker is a common problem in time-lapse movies, and is often caused by different exposures during the sequence. The better choice is manual mode.

Determine exposure using manual mode so it stays consistent for every shot. The ambient light in the scene might change during the sequence, but today’s cameras have great dynamic range and can handle slight exposure shifts. Next, focus on your subject and turn off autofocus. If your lens autofocuses for each shot, it might miss frames as the lens focuses back and forth. Shoot on a tripod to keep each frame identical in composition, critical when you make your final movie. Turn off any vibration reduction/image stabilization since the camera is stable on my tripod. Finally, set your white balance at a set value. Don’t use Auto and risk having the camera change white balance between exposures.

Once the camera is ready to go, it’s time to configure your intervalometer. This can be daunting at first. What is the right amount of time and delay between frames for your subject? Try this formula with simple daylight scenes like passing clouds or flowing water. Set your shooting delay for five seconds between frames and overall time for 25 minutes. You will capture 300 frames in 25 minutes, and a 24fps movie clip will be approximately 12 seconds long. For rotating stars at night, try using ISO 3200, a 20 second exposure at f4, and a delay between shots of five seconds. Focusing at night can be difficult. Try setting your camera to infinity focus, or using live view to help focus on stars. Make sure you have a fresh battery in your camera. If you have your Long Exposure Noise Reduction set to “on”, turn it off.

These shooting formulas are only the beginning. Experiment with your time between shots depending on the speed of your subject. Busy street scenes with people walking and cars driving past can be shot with a quick interval like 1-2 seconds. Slow moving subjects will require a longer interval between shots.

Here’s how to calculate an interval between shots: say you want to record two hours of time-lapse. There are 2 hours x 60 minutes per hour x 60 seconds per minute = 7200 seconds in two hours. Next, say you want to compress these two hours into a one-minute movie - that’s 60 seconds of movie. Dividing 7200 by 60 gives us an interval of 120 seconds or two minutes between exposures. After setting your exposure, set your interval to two minutes and off you go. Your camera will take one exposure every two minutes for two hours.

Another consideration is image quality. If you shoot RAW, you’ll need more compact flash capacity then if you’re shooting JPEG. RAW images will give you better options to adjust images after the sequence, but take a lot of processing power and more hard drive space.

Creating the time-lapse movie. Now you have the frames shot, it is time to make the movie. If you have an in-camera movie option, try that out first. Choose the movie quality settings before shooting the sequence, and the camera creates the movie after the all the frames are shot. Then simply download the movie off the flash card and it is ready to go.

Most time-lapse sequences are created in the computer with image editing software. There are many ways to create time-lapse movies including advanced workflows using Final Cut X and Adobe After Effects. But if you’re just starting out, one of the easiest methods is using QuickTime Pro 7.

This inexpensive software provides simple control of the movie creation. To start, you’ll need to convert your RAW files to JPEG or TIFF because QuickTime Pro 7 doesn’t work with RAW images. Next, put all your sequence images into one folder on your desktop. Open QuickTime Pro, and choose File-Open Image Sequence. Navigate to your folder of images, and select the first image in the sequence. Click Open, and choose the frame rate for your movie. We suggest 24fps for smooth video clips, but you can choose any frame rate you like. Once you click on the frame rate, QuickTime creates your time-lapse movie. You may have to minimize the window to see your movie (the movie often comes out as big as your screen or larger). Choose ‘View’ in the menu, and choose ‘fit to screen’. Once your time-lapse is created, you can edit and export the movie according to your desired end use.

Time-lapse photography is a quick and easy way to liven up your photography. The next time you are watching clouds race overhead, grab your camera and shoot a time-lapse sequence. You won’t believe how good accelerated time can look.

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.

Bring your IR images into Lightroom or Adobe Camera Raw (I assume you're shooting RAW). The first thing you'll notice is its red tint. OK, let's try adjusting WB. Can't do it - it's pegged at 2000K. If you use Nikon’s Capture or Canon’s DPP you can correct white balance but we can't do that in ACR or Lightroom. So, what can we do?

Here’s one method I really like:

Go on-line to Adobe and download and install the free Adobe DNG Profile Editor. Convert one IR RAW image to DNG (in Lightroom right click on the image and select Export/Export to DNG from the drop down menu). Now, open that image in the profile editor software (File/Open DNG Image). Go to the Color Matrices tab, grab the Temperature slider and move it to the left somewhere between -80 and -100. The exact amount isn’t important. Save the new profile – go to File/Export and either use the name provided or rename it something else (like “Infrared”). Exit and restart LR (or Photoshop). Now, when you open an IR image in Lightroom, in the Develop Module choose your new profile under Camera Calibration – Profile. You now have a much better place from which to start your post-processing. How much better? Go to WB and notice you'll have the entire range to the left to add as much blue to your image as you wish.

Once I have my WB where I want it, I go to Photoshop and make layer adjustments in Channel Mixer where I swap red and blue channels. Do this by setting blue to zero and red to 100% in the blue channel and visa versa. Then to Levels where, in the red and blue channels, I match up the black and white point sliders with the edges of the histogram. I might touch up the mid-tone levels as well. Sometimes adjustments in Hue/Saturation and/or Selective Color also help. I then save the image back to Lightroom for final adjusting until I get a false color image I like. I’ll also go into Black & White on some images using Lightroom or plug-in software like Perfect B&W in the onOne Suite.

Here's a before/after of a lavender field in Provence taken with the converted Canon G11.

Infrared is fun to shoot and, properly post-processed, you’ll be amazed at the results whether you shoot landscapes or portraits. And, by the way, while midday high full bright sun might cause you to put your "normal" camera aside, it's perfect for infrared.

Hope this has been helpful.

George

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