Technical Notes from our Photographer Fred Beutler

December 5, 2019
Let me end this lengthy series with some practical notes addressed to non-professional photographers.  These may be useful for your own photos, as well as those you send to our Rotary website. If I seem to emphasize the negative unduly, note that of the Ten Commandments eight tell you what not to do.  So I have a good preceptor.

But there are also positives among the Ten Commandments.  I will refer to the iPhone, which is the chief offender for bad images if thoughtlessly used.  You can control exposure and focus.  See https://iphonephotographyschool.com/iphone-camera-settings/.  There is no substitute for good composition (or cure for bad composition).  There are rules, such as the rule of thirds, which you can easily google.  But rather, follow your intuition: where is your principal subject, what will the eye follow when the viewer sees the picture.

Outdoor shooting is generally easiest, and yields the best results.  Avoid shooting into the sun; you will underexpose and people will look like dark silhouettes.   Avoid people squinting into the sun.  One mistake I see over and over is that people are such a small part of the overall photo that they are not even recognizable.  If you are using a smart phone, stand closer; if a camera, don’t zoom to a wide angle.  In that regard, know that a so-called digital zoom is a fake; it may make the image look larger, but only by cutting off the margins without improving the resolution.
Much of the above applies to indoor pictures.  Avoid backgrounds of windows; the bright outside light will underexpose the interior, and the white balance will be off.  You may want to use flash, which requires other considerations.  Be aware of the inverse square law, which says that the light of your flash illuminates objects inversely as the square of the distance from your camera.  I have often seen photos of people at long tables, those close to the camera being overexposed, and those further away underexposed.  With flash, also avoid mirrors of windows in the background; you will get a large white circular area, and everything else will be underexposed.  Finally, try to be at approximately the same height as the objects of your photo.  If these objects are inanimate, you will get exaggerated perspective.  With people, you get in addition enlarged craniums (from above) or exaggerated (double?) chins from below.
Selfie sticks are rightfully banned in many places, among them Disney parks, Westminster Abbey and Wimbleton.  Even the entire city of Milan has banned them.  And besides, they make for lousy pictures—one or two grinning faces against an unrecognizable background.  See also Leviticus 28:1ff “He who shows a selfie stick is unclean; it is an abomination.  He shall be unclean until the even.” (excuse sexism—it’s the Bible)
I promised to say something of post-production processing.  If you follow the advice above, you will not need any improvement in your pictures; in any case, you probably don’t have the equipment to do more than some elementary photo improvements.  There are too many (free) apps to mention that will help with exposure, contrast, cropping, both for the smart phone and a larger display device.  These can improve your image immensely.

November 20, 2019
The two advantages of JPG noted last week are the only ones: a smaller image file, and no need for additional processing.  On the other hand, a RAW file must be processed by appropriate software.  This software is always supplied with the purchase of a camera, but for more powerful software is available.  Photoshop is usually considered the gold standard, but it consumes considerable camera resources, and requires a steep learning curve.
The JPG image is processed quickly in the camera by a tiny CPU.  This tiny computer guesses the exposure, contrast, white balance without knowing the nature of the image; its calculation is based on an assumed “average image,” usually a neutral gray of 18% reflectivity.  Consequently, if the actual scene differs significantly from that average, there will be errors, especially in exposure and white balance.  We can try to use software such as Photoshop to remedy those errors, but the JPEG processing is at least in part irreversible.  Consequently, we end up with an inferior image.  An underexposed image  or one with a poor choice of white balance is particularly difficult to work with.
This is not the only deficiency of JPG.  The favorable small image property of JPG is achieved by a lossy compression algorithm.  The term “lossy” implies that each time we open and save the JPG file, there is a further quality deterioration.
The larger RAW file is processed on a computer outside the camera.  The computer CPU is much more powerful than that in the camera, and the photographer can take his/her time to achieve the desired effect.  One of the most important advantages is that, however we set the camera white balance, the RAW file is not really affected by the in-camera setting.  In other words, we are free to choose in our computer processing whatever white balance we deem results in the best image.  Another significant advantage is that all our RAW processing is reversible; any time we decide to make changes to produce better results, we can do so.  If we wish, we can even start all over from the original RAW image.
Next—and perhaps the final—time I will discuss “post-production processing.”  If that term causes you to roll your eyes, know that it simply refers to what we do in the computer to move from the RAW file to the final image.

November 14, 2019
Perhaps the greatest weakness of JPG lies in its choice of “white balance.” Different sources of light have different color temperatures, as expressed by a Kelvin figure. Kelvin is like Centigrade, except that its zero is absolute zero rather than the melting temperature of ice. This color temperature ranges from that of incandescent light (K~3000), which is predominantly yellow, to that of outdoor deep shadow (K~7200), which is largely blue. There are also other color factors, such as for fluorescent light, which has a nasty green component.

What our eyes see as white depends in actual color on the light falling on it. Our wonderful brain automatically compensates for the actual color, and sees white as white, no matter what light falls on the white surface. A camera, being dumb, records each surface according to the ambient light falling on it. To create the JPG image, the computer inside the camera applies its best estimate of the actual color of the image. The camera cannot know what the image is, so in processing to JPG it assumes that the image on the sensor averages out to a neutral grey. This works out all right for many occasions. On the other hand, if the chief object of the image is a yellow rose, the camera, in processing for JPG, interpreters the image as being a neutral gray object illuminated by incandescent light, and accordingly puts a blue tint over the entire image; this blue tint on top of the rose renders the JPG as a grey rose. You may have seen JPG processed photos which have an overall yellow tint, or seem to be blueish all over. These are the result of JPG processing misinterpreting the white balance. And once the JPG image has an incorrect white balance, correcting to the proper color balance is difficult, and sometimes even impossible.

This automatic in-camera processing to the JPG image can also give poor exposure, as when there is a small bright light in a dark scene. There are also other in-camera decisions, such as contrast and sharpness, which may be irreversible in any subsequent processing.

More of JPG and RAW next time.


November 8, 2019
The only two advantages of JPG over RAW:
  • The file size is smaller.  That makes the image easier to transmit, for whatever purposes.
  • The file is immediately available for printing or presentation.  RAW requires software (often furnished with the camera package) for the image to become available.
But JPG has many shortcomings.  As a lossy compression system, the quality of the image is reduced further every time the image is saved.  The image is not as good as the RAW image, even to begin with.  Simply put, you lose quality with JPG.  JPG is limited to 8 bit depth, whereas RAW usually gives you fourteen to sixteen.  There are advantages in dynamic range and in color separation.  A RAW image just looks better than a JPG image.
The JPG image, as it emerges from the camera, is already highly processed.  The camera CPU (CPU=central processing unit) makes decisions that are irreversible.  If it guesses incorrectly, it may well be—and often is—that the photo cannot be corrected.  These include decisions on exposure and contrast.  Here the CPU might erroneously read an extraneous bright light in a corner as being typical, so that the main subject is underexposed.   Or, expecting the overall colors to add up to a neutral gray, it may render a subject red rose into a pale shadow of itself.
Perhaps the most significant advantage of shooting in RAW lies in its treatment of “white balance.”  That’s reserved for next week.
Given the litany of shortcomings of JPG, modern non-professional digital cameras do remarkably well.  If your photographic endeavors revolve around photographing friends, families, and places you’ve been, keep on shooting in JPG.  Most of your pictures will be perfectly fine.

November 1, 2019
Explaining the difference between JPG and RAW involves an understanding of how a camera sensor sees light,  so I will cover that here.
Each pixel sees three primary colors, red,  green and blue (referred to as RGB).  All the colors and light levels you see are composed of various proportions and levels of these three components.  The respective levels are of course each digital, so that you can only see a finite combination of colors and light levels.  The nature of the color depends on the ratios of the red, green and blue output of the pixel, and the brightness depends on their amplitude.  When all the RGB levels are equal, we get a neutral grey.  So R=G=B=64, the color is gray; when R=G=B=128, the color is also gray, but it is twice as bright.  By the way, the human eye perceives brightness logarithmically, which is to say that the 128 level is seen only a little brighter than the 64 level.
Most non-professional cameras have a bit depth 8, which means each RGB has 2^8 levels. (Notationally, I can’t express an exponent in email, so 2^8 means 2 to the 8 power).  That means that each pixel can have (2^8)^3 or 2^24 different colors.  By this I mean to include also the dynamic levels; R=G=B=0 is totally black, which R=G=B=256 is totally white.  I note that professional cameras have a bit depth of 14 or 16, which can lead to much more nuanced colors and dynamics. While printers, projectors and computer screen cannot take advantage of this bit depth, the extra bit depth can be an asset, as I shall explain next week.
Next time, “white balance” and exposure.


October 23, 2019
I thought it might be fun to include with the meeting photos a little homily on photography for each of the several coming weeks.  So today we explain JPG.  Most non-professional photographers output their photos in JPG, while the majority of professionals prefer RAW.  Mext week we’ll talk about the difference of the two, and the reasons for this preference.
Technically speaking, JPG is an algorithm for a lossy compression system.  An algorithm is merely a sequence if steps whereby we compute something.  Compression means that we take a file and compress it into a file of smaller size, with the latter retaining “most”  of the same information as the original file.  A lossy system loses some of the information in the original file by virtue of the compression; that is the trade-off one makes with JPG compression. (A non-lossy system retains all of the information.)
In photography, the value of each pixel is likely to be roughly similar to those around it, so I can get at least a preliminary estimate for a pixel by taking a weighted average of those around it.  My data set, which originally consisted of the pixel value of each individual pixel, is reduced in size because I don’t have to carry each pixel value separately from all the others.  (Note that from what I wrote last week, with a color depth of 8, each pixel may have nearly two million different values.)
So the plus side of JPG is that we have a much smaller file, which is easier and quicker to transfer, and requires less storage space.  Usually, the loss in picture quality is small, and is not even noticeable unless we demand an extremely high quality product.
You can confidently continue to shoot in JPG, subject to a caveat I shall introduce next week.

October 16, 2019
Last week’s talk on the large figures involved in astronomy have inspired me to some photographic numbers.  My camera’s image size is 6016×4016 pixels (px).  Each pixel has a color made up of  three primaries (red. green, blue).  Each color has a color depth of 16, which means there are 2 to the power 16 colors.  So the camera is capable of taking 8.26e61 distinctly different pictures (the notation e61 means 10 to the 61st power.)
What appears on the website is less versatile.  For a typical 200×200 px photo, and a color depth of only 8, we get only 30 million possible different photos.  The figure is somewhat high, because the screen cannot produce all the theoretical colors.  The actual ones that can be produced constitute the gamut; all out-of-gamut pixels are reproduced by the closest in-gamut pixel.