Ed Schlotzhauer

An artists journey

Category: Photography

$Diffraction$
Diffraction
Today I would like to try to help us understand a little about what diffraction is. Not getting too deep in the theory. Just enough to demystify it a bit.
Scary
Diffraction is probably a scary word to most of us. Even if we don’t know what it really means, we have heard of it and have been taught that it is a “bad thing”.
Have you been taught to avoid using apertures smaller than f/11? Note that when I say a “small” aperture I am referring to the physical size. Remember that as the aperture numbers get bigger the actual opening in the lens gets smaller. This simple graphic illustrates that:
The lore is that very small apertures (large f-numbers, like f/22) make an image too blurry to be useful. Don’t believe everything you hear without testing it.
Light theory
I’m going very light on theory (yes, pun intended). We’re just going to graze the surface without taking a deep dive in. (Here is a source to start at if you want to go deeper. Abandon all hope ye who enter…)
Light behaves as waves (most of the time). Actually, a number of things are waves: light, water waves, sound waves, gravity waves. Quantum mechanics theorizes that even matter is waves. Too deep for me.
We tend to visualize light going through our lens as rays. That is, straight lines. Yes and no. That is one useful model of looking at it. But light also behaves as waves. An interesting and important property of waves is that every point on a wave is a wave. So if the wave is blocked by a small opening, the wave spreads on the other side of the opening.
This picture by Verbcatcher does a marvelous job of illustrating that for waves in water:
$Diffraction in water waves$
See how the waves spread after going through the small opening to the sea? The smaller the opening (aperture) the more pronounced the effect. That is, a small aperture opening causes waves to spread out more.
What does it really mean
This is the basis of the recommendation to use physically large apertures (small f-numbers). Apertures that are large relative to the wavelengths of light do not cause much “bend” of the waves. Small apertures (large f-numbers) “bend” the light more.
What we can actually see in practice is that using small apertures causes our images to have a mildly “fuzzy” look. Because the waves spread more after going through a small aperture, the individual waves cover a larger pixel area. This slight spreading of the light causes the image to appear less sharp.
The best discussion of diffraction for photographers I have found is from this article by Spencer Cox. But even this gets too deep into theory.
I borrowed this image from it to illustrate the practical effects of diffraction as we change aperture:
$Effects of diffraction with aperture$
See how the larger apertures (small f-numbers) are sharper than the smaller ones?
This illustration below, also from Spencer Cox) gives a great conceptual representation of what is happening. Take that the grid represents pixels in your sensor. At f/4, the point of light only strikes one pixel. It will be seen as very sharp. But at small apertures, the waves spread some onto adjacent pixels and create a kind of fog.
Should you fear it?
Should you fear it and always shun small apertures? No, it is just a reality of physics. It is no more to be feared than gravity. As one of my sons would say, it is what it is. Be aware of what is going to happen and consciously decide how far you need to go.
All of the exposure determinations we make daily are tradeoffs. How much to stop motion? How much depth of field do we need? Is there enough light for a good exposure? What ISO setting should I use? All of these things and more have to be balanced in the moment of shooting, besides composition and esthetic issues.
Each setting costs something. As experienced photographers we must understand the tradeoffs and be able to judge what is right for us at the moment.
Diffraction is one of those tradeoffs. Know what it is going to do and how to use it or avoid it.
Sometimes you need more
But why would we ever intentionally make our image less sharp? We seldom actually choose to make it less sharp, but sometimes we need other things. I can give 2 easy examples.
The first and most common one is to increase depth of field (DOF). It is counter intuitive, but making the aperture smaller increases the perceived depth of field. So on the one hand we are making the image less sharp, but on the other hand we are making it appear sharper throughout. When we need to make a certain range of the field of view acceptably sharp we stop down the aperture until we achieve our goal. A tradeoff.
© Ed Schlotzhauer
The second case that comes to mind is to reduce the shutter speed. I often intentionally shoot motion blur. But I usually forget to bring a neutral density filter for the lens I am using at the time. I can generally achieve the effect I want by using my polarizer, reducing the ISO to the lowest setting, and cranking the aperture down to the smallest possible one. This will probably give me a shutter speed in the range I want to use. Yes, the small aperture increases diffraction and makes the image less sharp. But it is handheld at a long shutter speed. It is already intentionally blurred.
© Ed Schlotzhauer
But maybe more importantly, in a great video on Lumminous Landscape, Charles Cramer said “sharpness is something we have to get over.” He explained that if we take a picture just because it is sharp, it probably won’t be very interesting. We have to forget about how sharp is it and instead react to the scene before us on an emotional level.
Shoot the picture
Diffraction is a side effect of physics and our photographic technology. Don’t be afraid of it. Don’t blindly follow some rule you learned in the past about what you can or can’t do. Understand enough about it to recognize it and know how to use it to your advantage.
Look at the image above of the woman’s face. Even at f/32 – an extreme case – it is acceptable. Extra sharpening can be applied in your editing tool to compensate for it.
So diffraction is just there. Allow it to happen if that is the tradeoff you need to make. Just like using a high ISO adds noise, that is acceptable most of the time and better than missing the shot.
I know many of us don’t want to deal with what we perceive as increased complexity or too much technical detail. We just want to go take great pictures. My hope is that topics like this will actually make your photography life simpler by providing some grounding for information you may have heard in the past. Rather than trying to remember rules for how to use your equipment, you now have a model for what diffraction is doing and how strong its effect is. I hope you will be able to stop fearing it and accept it is just part of the tradeoffs of the technology.
Today’s image
This is a great old WWII era truck I found in my town. It is a Coleman. This was actually a Colorado company. It was designed and manufactured in the Denver area.
I needed enough depth of field to span from the great rust and paint patterns on the near outside through most of the cab. So it is shot at f/22. Diffraction? Works for me.
What do you think?
September 18, 2024
They Told You Wrong About ISO
Many of us have a wrong idea about ISO settings. I will just say they told you wrong about ISO. It was a misunderstanding. Whoever “they” are.
Statement of faith
It is stated as a “strong suggestion“, especially when we are learning landscape or portrait work. Never shoot with ISO over 100. Maybe it is stated as only shoot at the native ISO setting for your camera. Either way, these are given as rules.
I hate rules, especially for my art. Rule of thirds. Rules of composition. Never put the subject in the center. Never shoot at midday. Always use a tripod. The list goes on.
Like with religion, most of the so-called rules are based on good ideas, but over time they are repeated as commands and the underlying reasons are lost. Just do it. (I don’t think that is what Nike meant.) The rules become a statement of blind faith that cannot be challenged.
What is noise?
All digital cameras have noise. Noise is randomly generated in the sensor and in the electronics of the signal path until the pixels have been digitized by the analog to digital converter (ADC). The noise is a fundamental property of physics.
The question is how much noise is there relative to the desired data. This is called signal to noise ratio in engineering. When we amplify a signal by increasing the ISO setting, all the signal including the noise is increased. This is why images shot at high ISO settings tend to look noisy. The image is usually not less sharp, but there is more noise obscuring things.
It is true for a low cost point and shoot camera or a high end medium format camera. What changes are the relative amounts of noise and the limits the image can be pushed to.
What is ISO?
You’re familiar with the exposure triad: the combination of aperture, shutter speed, and ISO that determine exposure. That’s it. Many other things affect the composition and quality of an image, but only those 3 control the exposure.
Aperture is the size of the diaphragm opening in the lens. It controls, among other things, the amount of light coming in. Shutter speed is the length of time the shutter is open to let light come in. And the ISO setting is kind of like a volume control. It sets the gain or amount of amplification of the sensor data.
Going way back to early film days, there were no agreed on standards for the measure of how sensitive film was. So a couple of the largest standards organizations (the ASA and DIN scales) came together and created a standards group under the International Organization of Standards. They adopted the acronym of the standards organization (in English) as the name. By the way, officially “ISO” is not an acronym, it is a word, pronounced eye-so.
Long way around, but now there are defined standards for exposure. For a given combination of aperture and shutter speed, the ISO settings on all cameras give the same exposure.
Why use higher ISO settings
OK then, in concept, the ISO setting is a volume control for exposure. Turning it up (increasing the ISO value) amplifies the exposure data. But as I mentioned, it is not free. Amplifying the exposure also amplifies the noise in it.
It is true that low ISO settings produce less noise in the captured image. Modern sensors are much better than early ones. This is one of the wonders of engineering improvements that happen as a technology matures.
Then, we should not use high ISO settings, right? Well, everything is a tradeoff. We need to use a minimum shutter speed to avoid camera shake when hand holding or to stop subject movement. We need to use a certain aperture to give the depth of field we want. These decisions must be balanced in the exposure triad, often by increasing the ISO.
Can’t I just underexpose?
When you accept that we must use the lowest ISO setting, the logical conclusion is that you could massively underexpose the image and “correct” it in post processing. Unfortunately this doesn’t work well. You are still boosting the noise unacceptably.
The camera manufacturer knows more about it’s sensors than your image processing software does. The camera’s built-in ISO amplification can take into account it’s characteristics and do a better job. And modern sensors and electronics do a very good job.
Are you wrong about ISO?
If you are following a rule dictating you must or can’t do something, yes you are wrong. There are no rules in art. No ISO-like standards body specifies what your image must look like. There are always groups wanting to do this (are you listening camera clubs?), but they have no authority.
If you are hand holding a shot, it is better to boost the ISO to steady the movement than follow a rule about using low ISO. The noise will be secondary to the reduced shake. Or I sometimes use the lowest ISO setting in my camera to create blur. I enjoy intentional camera movement (ICM) shots and will occasionally force an artificially slow shutter speed.
If it is night and you want to shoot stars or street scenes, are you not going to do it because you would have to violate a rule by the ISO police?
Use the ISO setting that lets you express what you want to do. It is your art. There are no rules. Besides, luminance noise looks like film grain. It can be an interesting artistic technique in itself. Do what feels right to you.
Apology
I used fairly strong language about this. The reality is that most photography writers have softened their recommendations on ISO. Most of them freely recommend using high ISO. This is healthy.
But I know many of us were “imprinted” by early mentors who left us feeling there was something dirty about going above 100 ISO. I want to free you if you still have those self-imposed limits. Using even a very high ISO and getting the shot is always better than missing it because you wouldn’t want to chance increased noise.
Today’s image
Since I’m advocating it, here is an extreme case that I’m happy with. This was shot hand held with an old Nikon D5500 camera – at ISO 22800. I have corrected out some of the luminance and chromance noise and I am perfectly OK with what remains. Getting the shot made me happy, even if the noise is high.
August 28, 2024
A Selfish Pursuit
When you think about it, most art, photography included, is a selfish pursuit. That is, it is about us, the artist. It is our expression. Is that bad?
Revealing what things look like
Go back to the mid 19th Century for photography and maybe a hundred years or more earlier for painting and one major reason for creating a work is to show people a (relatively) objective view of what a place looked like. People didn’t travel much back then, especially just for pleasure.
In the late 1800’s, unless you lived close to them, you would never have seen Niagara Falls, or the Rocky Mountains, or the Grand Canyon, or the Colombia River. Not in person. So there was a need for artists to show us these sights.
Artists like Bierstadt painted rather romantic and exaggerated views of scenery, like the Rocky Mountains. I hate to break it to you, but the Rockies don’t really look like this. A big selling point for photography was that it quickly captured “reality” (whatever that is). So photography brought views of places to a larger audience. This helped cement the false opinion that photographs are “real”.
Its been done
That was then. Now is different. Virtually every place has been photographed. I have a friend who specializes in wilderness photography – places few people have seen. But that is the exception, not the norm.
Now people travel long distances comfortably and relatively cheaply. And it is estimated that about 3 trillion photos are taken a year ( a trillion is 10¹², that is 1 million millions). So nearly every place people want to go has been visited millions of times and they have taken millions of pictures there.
We don’t need another picture of Niagara Falls or the Grand Canyon just to show people what it looks like. They have seen it. Many times. Too many times.
What is an aspiring artist to do?
Art now is about expression
What there is to do is to show a fresh, new point of view. I won’t say we must make a creative picture. That can easily lead to producing something different for the sake of being different. This leads to a lot of difficult to understand work that may not mean anything, but it is different.
It may be better to suggest we create work that is authentic. That is, it expresses our feeling or point of view and is also well done and artistic. Supposedly authentic work is fresh and unique because it expresses our own uniqueness. I cynically put the “supposedly” comment in because I’m not sure that many people actually have a refined point of view. A lot of people copy what they have seen someone else do.
Anyway, authentic work that expresses us should have a well reasoned and optimized composition, a look that is consistent with our other work, and an approach to the subject that reflects our feelings about it. It does not have to be of exotic locations or subjects unless that is what we are drawn to. Actually, the subject matter can be mundane and common if we have a fresh approach to it.
I have to do it first for me
Therefore, I claim that art is a selfish pursuit. I have to do it for me, to express what is drawing me to the subject. If it is liked by other people, that is a plus. But if I create the work mainly to please others, I lose sight of my own uniqueness. I miss out on bringing the viewer something new because it is something that comes out of me.
So in this special case, be selfish. Think of yourself first. Create art that pleases you. Other people will be drawn to the passion that is obviously there. They will ignore lifeless copies of what they have already seen.
Today’s Image
This was in downtown Denver one time. I was grabbed by the patterns and lines and reflections. I had to do something with it. The herd of people traveling through in a protected bubble, probably oblivious to most of the beauty around them, really got me.
August 21, 2024
Why Do It?
Here’s a dirty secret of the photography world: we don’t make much money on fine art sales. Then why do it?
Crowded market
The art market in general is crowded, over-saturated, cutthroat. And photography is even worse. Everyone is a photographer. Trillions of images are shot every year. If only 1 trillion pictures are taken a year, that is an average of over 2.7 billion pictures a day. Who has time to look at anything anymore?
And people have come to view photographs as some pixels on their phone screen. They quickly scan through hundreds of them a day. That devalues art in general and fine art in particular.
Even if your work is excellent, how do you get people’s attention? Not many people go to galleries. If you are looking for a nice image to go over your couch or fireplace, where do you go? Etsy? Art Marketplace? Amazon? Maybe, but you will quickly drown in choices. Some of them are good.
Other channels
The fine art photographers I know who are making money sell through galleries or art fairs. But even that generally does not support them.
No, most “professional’ fine art photographers support themselves through conducting workshops or selling online courses or writing books. There is still money to be made there. Seems like everybody is a perpetual beginner and needs training. A photographer who makes a name for himself can do well teaching other people.
Fine Art
I keep saying “fine art” photography. That is what I generally do and what I like. It is a small niche of the overall photography market.
People whose main motivation is selling art are told, rightly, to go to Art Marketplace or Amazon or places like that and research what people are buying. Then do more of that. Following the crowd is a sure strategy to sales.
That is not what I do and I do not want to do it. I am interested in creating art – exploring and using my creative vision – instead of copying what other people are doing.
Self motivation
I would love to sell more of my prints. ( photos.schlotzcreate.com or contact me ed@schlotzcreate.com 🙂 ), but maybe not for the reason you would first think.
In my view, my art will be expressed mainly as prints. A print has many great qualities that are well beyond what a screen can provide.
I want people to appreciate my work enough to pay for a large, excellent quality print to put in their home or office. Something they want to look at frequently over the years because it stirs something in them. It creates a relationship between us, between my vision and its effect on their life. I want to know who is buying the print and why. To me, another nice nighttime shot of the Dallas skyline they buy off Amazon does not do that.
I spent a great career as an engineer, but I kept alive a secret desire to express my creativity through photographic imagery. It is one of the important things I do to keep growing as a human. I don’t actually have to support myself financially through my art. I can be selective. Call me privileged if you want, or call it good planning and knowing how to build a good life.
Can’t not do it
So I have a strong desire to share my works with people, to have them resonate with some of them enough to decide to buy them to look at for years to come. I hope my art will add something to their lives.
But if no one sees my work and no one buys my prints, I still have to do them. Ultimately, my art is for me. It is something I need to do, that I am driven to do. My art completes something in me. It is something I can’t not do.
I have long since given up on the romantic notion of becoming rich and famous through my art.
Today’s image
I can’t pass up something like this. The simplicity and distinct graphic lines grab me. In this case, I risked getting fired, because I took it at a company I worked for where they had a strict no camera policy. But I walked in this door every day and when the light was right… Well, I couldn’t stop myself.
August 14, 2024
The Histogram is Just Data
I don’t mean to be insulting, but I cannot understand when people look at histograms as some magical, mysterious, and intimidating technical artifact. It is not. It is just data about what our sensor is seeing. The histogram is just data, and it is useful. Use it. Do not be afraid of it.
Trigger
A newsletter I received today triggered this semi-rant. But looking back, I see it has been over 3 years since I wrote about histograms, so it is probably time to revisit the subject. This actually is a subject I feel some passion for and believe it needs to be better understood by photographers.
The newsletter author declared that our histograms lie. I realize that click-bait is commonly used to try to get people to read articles, but I still feel it is being somewhat underhanded. Now, in fairness, the newsletter author made some valid points – except for the part about histograms lying.
What is a histogram?
We see this graph of some data and maybe it does look complex and mysterious if you are not used to working with data and don’t know where the data comes from. Let’s get over that by understanding how simple but effective it is.
By convention we play like our cameras measure light in a range of 0 to 255. There are no units: 0 represents black and 255 is pure white. The convention came from the history of early digital cameras. It is obsolete today, but still used. That is a topic for another day.
So there are 256 possible values of brightness (0-255). If we go through and count the number of pixels of each value – the number of pixels in the image that have value 0, the number of pixels in the image that have value 1, etc. – and put them on a graph, we have a histogram.
Here is a simple example:
Again, black is on the left going to white on the right. Even without me showing the actual image, we can see that there is a “bump” of dark values on the left and a larger hill of bright values on the right. In between is a relatively low and even count.
What can we learn from this? It is a black & white image, because there is no separate data for red, green and blue. There is high contrast because of the hills at the dark and bright ends. It is bright but not overexposed. There are deep blacks, but not enough to have lost important information. So, even without seeing the image, we can tell a lot about it. Is the image exposed “correctly”? Ah, that is the question my rant is based on.
This is why histograms are useful. They are useful data about our image. It gives simple information to help us understand our exposure better.
Benefit
Today’s mirrorless cameras bring us the amazing benefit of real-time histograms. We can select to see the histogram live in our viewfinder or on the display on the back.
What is the benefit? We see an immediate graphical view of the exposure the camera is determining. In the example above, we can see that the light tones are very bright, but not overexposed.
I routinely use it to watch for “clipping” of brights or darks. If there is a large hump of data jammed up against the left or right edge, that is probably a problem. I will often choose to override the camera’s exposure determination to avoid these peaks.
Again using the example above and knowing that my camera was in aperture priority mode, we see that it chose 1/750 second as the shutter speed. That works OK in this case, but if I did not agree, I would have easily used the exposure compensation dial to adjust the exposure. I do this a lot.
So the histogram is a quick and easy to get a feeling for the “shape” of the exposure.
They don’t lie
Now coming to the basis of my rant: histograms do not lie (actually, they do; I will say how later and why it doesn’t matter).
The newsletter author gave the example of a picture of some fruit on a dark table with a black background. She said the histogram lied because the camera did not give the exposure she wanted. It tried to make the whole image evenly exposed.
No, the histogram is just a straightforward measurement of the data. If you take your temperature but don’t like the reading you get, it is silly to say the thermometer lied.
What the author was describing was that she wanted to expose to have the same look as the scene she saw. This was a case of disagreeing with the camera’s matrix metering calculation. It was doing it’s job of trying to capture all the data that was there and preventing blown out blacks. But she decided to use exposure compensation to force the camera to expose the scene the way she wanted.
The histogram did not lie. As a matter of fact, she relied on it to do her exposure compensation values. She used the histogram to determine how to override the camera exposure calculation.
Actually, I would have used the camera’s original exposure determination. I like to have all the data available to work with. This is called exposing to the right. Bringing the brightness down in post processing to the level she wanted is simple, non-destructive, and does not add noise. Capturing the compensated image the way she wanted irreversibly crunches the blacks.
They lie
I said they don’t lie, but they do a little. For speed and efficiency the histogram is derived from the jpg preview of the image. Same as the preview shown in the viewfinder or camera back. If you study jpg processing you will see that it alters and discards a lot of information to give a good perceptual result.
So the histogram is not actually looking directly at the literal RAW data from the sensor. But there is little observable discrepancy. On my camera, I find that it exaggerates the highlight values very slightly. Still, I typically back the exposure off to avoid highlight clipping, so it adds a little conservatism into the process.
Trust the data you see. It is good enough.
They’re not the photographer
The histogram gives you data. It does not determine exposure. People talk about “good” or “bad” histograms. This is a misunderstanding. There are no absolute good or bad ones. What counts is did you get the exposure you wanted.
There are valid artistic reasons for shooting what some people would consider bad histograms. If it is what the artist wants, it is correct.
Histograms give us a reading of the exposure. They do not determine what is right. It gives some insight on what the automatic exposure calculation in the camera is trying to do.
Use it
The histogram is a brilliantly simple and wonderfully useful tool. We are lucky to have real-time histograms available to us now. It is a game changer. But it is just data. Do not be afraid of it.
The histogram does not lie. But it does not automatically ensure that the exposure is exactly what you want. You have to sometimes take change and override the camera settings. When you do, the histogram is there showing you the result of your decisions.
It is not magical or mysterious. It is a great tool. Use it. A craftsman know how to use his tools.
August 7, 2024