Learning photography – Page 14

What is a histogram in photography?

A histogram is an illustration of how light is distributed across the tonal ranges in your frame. You have black to the left, white to the right, and shadows and highlights in between.

What is it for?

Let me first say that photographers have for many years taken excellent photos without any histograms. So you can do well without them. Some absolutely love them and others shy away from them. It is all up to personal preference.

As the histogram shows you how light is distributed across the tonal ranges, it gives you good insight to the exposure of your image: where is the “weight” put in the tonal range?

If it it under exposed, then the graph is heavy to the left (lefty as some say).

Is it over exposed, then the graph peaks to the right.

If you loose details in the dark areas, then the graph touches the left hand side. If you clip the highlights, then the graph touches the right hand side. If it touches both sides, then you have a high contrast scene and exposure bracketing may be a way forward.

Some histograms show only the red, green and blue color channels in one combined graph whereas others split them up. In the image above, you can see that my Fuji X-T20 show both the color channels and the combined result (grey – on top).

Some make rules based on the histogram, like: your histogram should be evenly distributed and center weighted! Others run away when they hear such rules – the option to use over- and underexposure as a creative tool should not be hampered by rules that restrict your creativity.

Either which way you look at it, the histogram gives information about your exposure and if and how you choose to use it is up to personal preference.

Where is it?

If you are so lucky to have a mirrorless camera, it is very likely that the electronic viewfinder (EVF) can show the histogram as and integral part what you otherwise would see in the viewfinder. And it will even update the histogram as the light in the scene changes. This is very convincing.

A DSLR does not have this option in the optical viewfinder, but if you shoot in live view mode then it may be able to present a histogram in the rear LCD just like the mirrorless does in the EVF.

These options are all before you hit the shutter. Post shooting, you can review images in the rear LCD and here most modern cameras can show the image with a histogram. Just as the picture in the start of this post shows.

In post processing software like Lightroom, you also can see the histogram, and as you pull the exposure slider there, you will be able to see the changes the editing does to the histogram.

What is an ND-filter?

Definition and use of a Neutral Density filter.

An ND-filter or a neutral density filter is like a pair of sunglasses that you put in front of your lens. The purpose it to reduce the amount of light that hits the sensor, just like you want to protect your eyes from the strong light on a sunny day.

A variable ND-filter sitting on my beloved Nikkor 16-35 mm lens.

The point with an ND filter is to allow you to keep the shutter open for longer time without clipping the highlights in your picture or in other words simply avoid that you over expos your picture.

Why would you then want to keep the shutter open for a long time? Take a look at the picture below. It is taken over several seconds. The stones of course do not move, while the waves of the sea are reduced to pure silk. Moving parts become blurred, stationary items stay sharp. That is one effect you can get with an ND filter. You can also shoot waterfalls, harbors, etc. with this technique and get similar results.

Long exposure. The stones stay put, the waves of the water are reduced to pure silk…

Another application is simply that there is so much light that even when you shoot at the fastest shutter speed your camera offers and base ISO, you still get too much light. Then an ND filter – like sunglasses – comes in handy to reduce the amount of light.

You can also use the long shutter opening to move the camera instead, and this is what is done in intentional camera movement where you move the camera to create a blurry effect.

ND filters come in variable and fixed ones. I prefer the variable, because I can then turn the ring to reduced effect (ND8), so I can actually see what I am shooting and then once focused, return the ND filter strength to full throttle (ND2000) and get the most out of the filter. If you have a filter with a fixed value, you typically find you have to take it off the lens in order to focus, and the re-mount to take the picture. The variable filter saves you a bit of work.

The light reduction your ND filter yields is typically measured in ND values – if you look at the picture of my ND filter above, you can see it ranges from ND8 to ND2000. That is a reduction of 3 stops to 11 stops. That is a lot! You may be able to get by with less than that.

ND filters are not cheap, and you want to get a good one. The “neutral” in ND is to be taken very literally – you don’t want the ND filter to change the color or toning of the light. It should really stay neutral. Cheap filters unfortunately often has this un-wanted side effect. Make sure you get a filter with good reviews – it is quite expensive, yes, but you will not enjoy a filter that alters the colors. Believe me – been there, seen it, done that. Not to be repeated.

What are exposure metering modes?

Outlining the various exposure metering modes that a modern camera offers.

Exposure is vital

Unless you have a very old vintage camera, it is most likely that a light meter is built into your camera!

A good old light meter from back in the days when a meter was not so common as an integral part of the camera…

The light meter measures the amount of ambient light available and based on this, the camera can choose camera settings (aperture, Shutter speed and ISO) to get a correct exposed picture. (PS: Take the wording “correct exposed” with a grain of sand, as exposure can be used as a creative tool and hence “correct exposure” is more the technical correct exposure.)

The meter in your camera can read the light in different ways and give priority to different aspects to help you get the exposure you want. Mind you that the camera has no idea what it is you are shooting, so any help you can give it will help bring the exposure closer to what you are after. The exposure modes are just different ways of reading the light.

There are variations in how the different camera manufacturers name their exposure modes, but the principles are roughly the same. Here I use the names from Nikon, but when you read the manual for your specific camera, I am sure you can recognize the different modes.

Spot metering

Spot metering measures the light only in the focus point or in area just around it. It ignores the amount of light in the rest of the frame. This pin prick way of measuring the light makes it possible to have blown out areas or loosing details in the shades with no problem – the camera only meters the focus point. This is useful if you want to make sure than the eye of a person is correctly exposed in a scene where there is lots of either bright or dark areas or both.

Center-weighted

Center weighted metering takes the entire scene into account, but gives more priority to the center of the frame. This is a classic metering mode for portraits, as it helps get the person exposed well, with less weight to the outer parts of the frame. This of course provided you put your subject in the center of the frame! You can via the menu system control how much emphasis the camera is to put on the center part relative to the rest of the frame.

Highlight-weighted

Highlight weighted takes the brightest area of the frame and makes sure it does not get blown out, but on the other hand ignores that details are potentially lost in the shadows. In other words, if there are very bright areas in your frame, this mode will deliberately under expose your picture to secure the highlights are preserved. Very useful if you are shooting with the sun or some spotlights in the frame and want to preserve all the details in the bright areas.

Evaluative / Matrix metering

The matrix or evaluative metering takes the entire frame into consideration when metering the light. It is the most automated of the metering modes, as it gives a good balance between bright and dark areas. However, as it is a highly automated mode, the camera will try to find the “middle of the road” and make compromises to make the best of the scene without knowing what you shoot.

What should you choose?

If you don’t know what to choose, the evaluative / matrix metering is the option to go for. It gives you a good compromise and many photographers never leave this metering mode. And if you shoot RAW, there are lots of options for working with the exposure in post to recover details in the dark or details in the bright areas.

I typically shoot in RAW and use the evaluative / matrix metering. If I shoot where the light is very harsh, for example in the middle of a summers day, then I switch to the highlight weighted mode to avoid blown out parts, but I do so knowing that I may loose details in the dark.

All of the above is less relevant if you shoot in the automated mode (i.e. not P, A, S and M). In the fully automated mode (green A on the mode dial) the camera ignores your metering settings and makes its own decisions!

Thank you for reading this far! Questions and comments are more than welcome!

What is lens flare?

Lens flare is bright areas of light in your image, that you do not find in reality! It is caused by the way light hits the front side of the glass in the lens and is scattered inside the lens.

Here below I have taken a shot of me holding my iPhone up in the dark and taking a picture of it. You see leftmost a hectogon shaped green light (the same shape as the aperture blades) followed by several colored bright spots. This is flare. None of these were there when I studied my iPhone with the naked eye:

A bright light source (here from an iPhone – more typical the sun) in stark contrasts often brings out lens flare.

If the light comes into the lens from a very steep angle, then the result can be a milky white area – sometimes covering the entire frame. And the contrast in that area is significantly reduced – things appear to be washed out.

Here I hold the light from the iPhone so it comes into the lens from almost 90 degrees and from the left. If you’re thinking: 2001: A space odyssey, then you know what creative tools Stanley Kubrick used.

If you want a good test if your lens has flare, go out at night, find a tall lamppost and point your lens towards it. Move the light from the lamppost in and out of the frame to provoke flare. You will probably be able to get some flare effects, especially if you leave the lens hood at home and choose a zoom lens. Zoom lenses have more complicated constructions than primes and tend to produce flare more easily.

Some love flare. In my experience, videographers love flare. When you watch TV or go to the movies, you will quickly spot flare used as a creative tool. It certainly underlines the strength of the sun on a sunny day. Also some photographers love flare, they even add it to the image in post processing!

Others do not love flare so much. If you want realism in your photos, the flare is to be avoided, as it is a thing created by your lens. It sort of gives away that a lens was part of producing the image.

Some lens constructions are better at reducing flare than others. Modern coating of the lens glass greatly reduces flare, but cannot eliminate it fully. Zoom lenses have more complicated constructions and are hence more prone to flare – primes less so. And finally, you can use a lens hood to reduce the flare. I sometimes even hold the hand against the sun to protect my lens from getting the light that produces flare.

In my opinion there is no right and wrong when it comes to flare. It is a creative tool. The problem comes when it is there and you don’t want it or the other way around. But hopefully this article has given you some ideas what to do in these cases.

Thank you for reading this far! Questions and comments are more than welcome!

What is chromatic aberrations in photography?

What CA is and what you can to about it!

Chromatic aberrations, often abbreviated to CA, is lines of color, typically along high contrast areas in your image. These lines do not reflect what the lens actually saw – it is created in the lens as the light travels through. It is also known as purple fringing or color fringing. So your lens simply adds a line of color along a high contrast area.

Chromatic aberration – notice the line to the right of the stem…

In the image above shot with the Nikkor 28-105mm (formerly a kit lens), the CA is really bad – notice the vertical line that follows the left hand side of the stem, but also all the leaves with white background suffer from serious CA – they are almost more purple than green!

The reason for this is a fault in the lens, where it does not manage to align the different wavelengths of light correct. The reason can be the lens design, slight movement of the glass over years (wear and tear simply) or a combination of the two.

If you notice CA while shooting, you can try to stop down the lens a bit, i.e. go to a higher f-stop number. CA is known to be worse at wide apertures, so this may help you reduce the problem.

Your post processing software can remove some parts of the CA, but not necessarily all. Lightroom has different sliders that you can try to use, if the standard checkbox “remove CA” does not work. I find that in many cases it works, but there are still a few images where I have not been able to remove the CA. If the CA is too bad and it cannot be removed in post, the only option left is to convert the image to a B&W image, as the CA is reduced to a slight blur in the image.

What is focus breathing?

When you zoom in and zoom out you expect the effect to be a change in angle of view, i.e. that the subject moves closer to you or further away.

When you turn the focus ring on your lens, you expect the lens to move the focal plane back and forth to focus on different subjects in the frame.

Focus breathing is when your lens does both at the same time! As you turn the focus ring the angle of view changes as well. In other words, the closer to yourself you zoom, the shorter your lens becomes! For example the Nikon 70-200mm f/2.8 is actually a 120mm when it focuses to minimum focus distance at 200mm!

Focus breathing is for most of us not an issue, but in two cases it can cause you a headache:

In a scene where you have two persons in the frame talking to each other and you want to focus back and forth between the two as they speak, you really don’t want to change the angle of view. It needs to be constant, otherwise the viewer gets confused at best, and a bit seasick at worst. You want that framing to be constant. For this reason, videographers absolutely do not like focus breathing.

Macro photographers struggle with focus breathing when doing image stacking, that aims to compensate for a very shallow DOF by blending images that have been shot of the same subject with varying focus points. Here you absolutely need the framing and angle of view to be constant, otherwise the image will look very strange or at worst your post processing software wont be able to blend the images.

So should you worry about focus breathing? Not really, if you ask me. Only in the two above specific cases would I worry.

Of course it can be annoying to know that your wonderful lens has focus breathing, but now that you know what it is and in which cases it is a problem, in all other cases you can disregard focus breathing.

Thank you for reading this far! Comments and questions more than welcome!

What is lens distortion?

A short description of lens distortion, the two main types and to what extend you as a photographer should worry about distortion.

Straight lines…

Lens distortion is when a straight line in reality is not represented as a straight line in your image. It is caused by the lens and the way the lens glass elements shape the light on its way to the sensor or film in your camera.

Barrel distortion makes the center of the image pop out to appear closer to you even if the wall with these tiles is as straight as they come!

Modern lens constructions seldom have significant lens distortion, as the lens designers know that reviewers by tradition will test the lens for distortion and make a point of it if the lens suffers from distortion. In reality, most of us will never notice the distortion, and only if you shoot architecture, real estate or landscapes with edge-to-edge horizons will you notice the potential distortion in your lens.

Pincushion distortion makes the center of the image appear further away….

Wide lenses, i.e. lenses with a short focal length, suffers more from distortion than longer lenses. The wide field of view that a wide lens has makes it more of a challenge for lens designers to make the edges of the image free from distortion. A good example where the designers deliberately have given up is a so called fish eye lens (say 8mm focal length), where the distortion to a large extend is the point.

In Lightroom and similar editing tools, the lens profile is available to the software and hence the distortion can easily be corrected in post, just by ticking off an option during post processing. In some cases the camera and the lens in combination is able to remove the distortion as part of the cameras internal processing of the image, and hence the image that you find on the memory card of your camera is distortion free from birth.

Thank you for reading this far! Comments and questions more than welcome!

What is ISO?

Forget the sensor sensitivity!

Back in the days when everyone shot 35mm film, you could get films with different ISO levels, say ISO100 or ISO400. You could actually by buying a different film change the ISO. Also, this gave rise to the term the exposure triangle consisting of shutter speed, aperture and ISO. But that was back in the film days. Today, when your sensor leaves the factory, the sensitivity to light is fixed. So no changes to ISO as we knew it from the film days. But turning up the ISO will give you images that look more exposed than images with lower ISO’s, so what is going on?

Turn up the volume!

When you listen to radio and the signal gets bad with lots of noise, what do you do? Yes, you can turn up the volume, but that will both amplify the noise and the signal, so my guess is that you turn the knob for controlling the tuning, in order to get a better signal. Turning up the volume will not help.

So what is ISO in a digital camera? After the camera has taken the picture and the sensor has read the light, then the ISO is applied in the cameras internal post processing! It takes the signal and amplifies it as ordered by the ISO setting. The higher the setting, the more the amplification. But just like the old analogue radio, both the signal and noise is amplified.

That is why ISO is no longer part of the exposure, as it is applied after the exposure. The exposure triangle is now only aperture and shutter speed. Your sensor has the sensitivity it had when it left the factory.

What is it good for?

If you set your ISO to the cameras base ISO, typically ISO 100 or ISO 200, then you will get the cleanest images. As soon as you crank up the ISO, the price you pay is more noise and more grain. Luckily, most modern cameras have algorithms that are pretty good at separating noise from signal, so you can get good results at ISO 800, ISO 1600 and even ISO 3200 or higher. You can continue the work with optimising the image in post and get good results with even higher ISOs that that.

More modern cameras can go to higher ISO values than older ones. The reason being that the computing power in modern cameras has increased and hence there is capacity (“horse power”) to run advanced noise suppression algorithms in the camera. The better the noise suppression, the higher (meaningful) ISO values can be applied.

The reason why you would turn up the ISO is lack of light. It is a simple as that. Maybe you want to shoot something that moves very fast so you need to reduce the shutter speed? A high ISO may be the compromise you need to get images that are sufficiently exposed. Maybe you want to shoot at a very narrow aperture to get lots of (DOF)? That narrow aperture won’t let in much light, so ISO could help you out.

There is no free lunch when it comes to photography. It is one big pile of compromises. But subtle use of ISO may be just what helps you out when you lack a little bit of light. So give it a try and you will over time find out where the limits for your use of ISO subject to what you shoot.

Video link

What is Depth-Of-Field?

A short definition of what Depth-of-Field in photography is…

Acceptable sharpness

Depth-of-fields (DOF) is the area (depth) in which subjects in view of your lens appear to be acceptably sharp. The DOF area closest to you is called the DOF near limit, and the other end the DOF far limit. Within that interval, subjects appear to be sharp.

If you have not tried to focus manually, I encourage you to try so. Flick the little switch on the front left of your camera (typically) from AF to M, and try to turn the focus ring manually. Notice how different parts of the scene becomes sharp as you turn the ring. You are actually “pushing” the focal plane back and forth when you turn the focus ring – the focal plane being where you as photographer decide the image is to be sharp, but there is an element of “forgiveness” prior and after the focal plane and that is the DOF.

DOF illustrated

I think of the DOF being around 1/3 prior to the focal plane (the focus point) and 2/3 after the focal plane, but this is not a technically correct way to see it, but if you like me just want to have a drivers license to what DOF is, then this is a good and operational way to think about DOF.

Your DOF depends on many factors such as the distance to the subject, the sensor size, most notably the aperture and the length of your lens. Most photographers work with the aperture to control the DOF, but you can also use the distance to the subject.

Macro photography

Macro photographers suffer from the fact that when you are super close to your subject, the DOF shrinks to almost noting, even if you pump up the Aperture to something crazy high – it won’t help, as the distance is so small that you get a paper thin DOF no matter what. Therefore many macro photographers use focus stacking, where you take several images and change the focus point, and then in post merge the sharp parts together to create an image with a larger DOF.

Portrait photography

Portrait photographers use a relatively small aperture to shrink the DOF so that the background becomes very blurred and hence does not take focus from the subject. You can also get this effect at a higher aperture (and hence DOF) if you just make sure that the distance from the subject to the background is by factors way bigger than the distance from the lens to the subject.

Category: Learning photography

What is a histogram in photography?

What is it for?

Where is it?

Further reading

What is an ND-filter?

Further reading

What is shutter speed?

What are exposure metering modes?

Exposure is vital

Spot metering

Center-weighted

Highlight-weighted

Evaluative / Matrix metering

What should you choose?

What is lens flare?

What is chromatic aberrations in photography?

Related reading

What is focus breathing?

What is lens distortion?

Straight lines…

What is ISO?

Forget the sensor sensitivity!

Turn up the volume!

What is it good for?

Video link

Related reading

What is Depth-Of-Field?

Acceptable sharpness

DOF illustrated

Macro photography

Portrait photography

Further reading