You probably heard the term “megapixel war” and that manufacturers try to top the number of megapixels their camera or smartphone offers. So you could get the impression that more is merrier, but there is more to the equation than that…
Resolution
If you look at a chessboard, you can see it has 8 squares across by 8 squares up, in total 64 squares. So if your chessboard was a camera sensor, it would have a resolution of 64 pixels. Indeed not a lot, but it goes to show the principle of each “dot” that enables the camera sensor to register the amount of light it is exposed to.
My Nikon D750 camera has 6016 pixels across and 4016 up, giving a total of 24.160.256 pixels, often abbreviated 24 megapixels or 24MP. For most photography this is more than sufficient resolution unless you crop your picture, which in effect takes away some of the pixels and hence the resolution.
Bit depth
The bit depth tells how much information your camera is able to store per pixel, i.e. the size of the number per pixel. JPG files store very little information per pixel – only 8 bits known as a byte, and hence it is able to store 2^8 = 256 different values (This is per colour channel, but lets leave that aside for now).
If your image is a RAW file, the format allows you to store 12 (or 14) bit of information. This gives a much finer granularity in the tones and colors that can be stored, but it also comes with a price: the file is much larger, as the information stored per pixel is dramatically increased.
No chain is stronger than…
Many only consider the resolution as an important parameter, but the bit depth is equally important, as it enables you to store the specific reading of light from the sensor. However, you also need a good lens to let through good light with all the details required to capture the scene, so if you put a poor lens in front of a high resolution sensor that captures in RAW, the only thing the sensor will register is precisely how bad the lens is.
So you need all the elements in the chain to work together: lens, sensor resolution and sensor bit depth, in order to get the best possible image captured, with good resolution and contrast.
So if you have a good camera that can capture say 24MP in RAW format on a good sensor, the limiting factor is probably more the lens that you put in front of it than the resolution of the sensor. And that is why any experienced photographer will tell you: invest in good glass before anything else.
ILC is Interchangeable Lens Camera, basically meaning that you are able to shift between different lenses. The opposite to an ILC is a camera that comes with the lens fixed – as you know it from your smartphone or a point and shoot camera like the Sony RX100.
Although ILC judging from the name should cover all types of cameras with interchangeable lenses, the term ILC for reasons beyond me often is used to describe mirrorless cameras with interchangeable lenses. If the camera has a mirror built into it, the term DSLR is more frequently used.
To mitigate this confusion, some use the term MILC instead of ILC to underline that it is a Mirrorless Interchangeable Lens Camera they are talking about.
SLR is an abbreviation for Single Lens Reflex. It simply means that there is only one lens and that you via a mirror look through the lens that sit on front of your camera. This is as opposed to a rangefinder camera, where the viewfinder gives you a preview of the scene based on another lens that what the camera will be using to capture the image. Hence only a single lens in a DSLR.
The mirror flicks away when you take the shot (and it makes a noticeable noise). This is why you will see the viewfinder go black during the exposure – the light is sent to the sensor rather than the viewfinder.
The D in DSLR is Digital, as your camera has a digital sensor rather than a piece of film. So it is Digital Single Lens Reflex camera or DSLR.
A mirrorless camera (ML) has no mirror and simply sends the light directly to the sensor, that then via a small electronic viewfinder (a small TV!) presents the preview for the photographer in real time.
PASM is abbreviations for program, aperture priority, shutter priority and manual exposure modes. You typically find these modes on a dial top left of your camera. If you are shooting Fuji, you will not have a PASM dial – the camera figures out the mode based on your selections.
The PASM dial on a Nikon D750. Most manufacturers name the modes the same way you may find that S is called Tv and A is called Av.
The point with the PASM dial is to control how much control you have of how correct exposure is achieved. You may recall that the exposure triangle gives 3 variables to control the exposure: Aperture, Shutter speed and ISO. Lets get back to ISO a bit later, as ISO is not controlled by the PASM dial.
(P)rogram mode: Camera controls aperture and shutter
(A)perture priority: You control aperture, camera controls shutter
(S)hutter priority: Camera controls aperture, you control shutter
(M)anual mode: You control aperture and shutter
So what is the point with different degrees of control? It all comes down to what it is your are shooting and what you want to achieve. Not a very helpful answer, but some examples might help:
Lets say you want so shoot something that moves very fast and you want to freeze the action. In that case you want to secure that the wings for the bird for example are not a big blur but is captured razor sharp. So here shutter priority is a good choice, as you set the shutter speed to say 1/1000th of a second and ask the camera to adjust the aperture to get a correct exposed image.
In another situation you are shooting a landscape with very little moving parts. But you want to have as much of the landscape sharp as possible, so you set the aperture very narrow to maximize the depth of field. You leave it up to the camera to determine the shutter speed.
The thing to realize is that your camera, no matter how clever it is, cannot tell what it is you are shooting. Only you know that. So if you go for the automated (P)rogram mode, you get some “middle of the road” camera settings that may not work for what it is you want to achieve. So by taking the camera out of the automated exposure mode (P) and move to the semi automated modes (A) and (S), you get more control. And the top of the pop is manual mode (M) where you can control both shutter speed and aperture at the same time. This can be used for example to deliberately under or over exposing your image to achieve a high key effect. It all comes down to what you want to achieve.
What is then the difference between Auto mode and Program mode? You probably have auto mode as a green option on the mode dial on your camera. In auto mode, the camera controls EVERYTHING – you are really going with an auto pilot here. In program mode, the camera only automates the exposure settings – you control many other options, for example if a flash is to be used or not. In auto mode, the built in flash (provided your camera has one) pops up as soon as the camera finds there is too little ambient light.
What about ISO then? ISO is typically controlled irrespective of the exposure mode. You can control ISO via the menu system and sometimes via buttons on the camera body. ISO comes in 2 option: Auto or a specific value. If you set the camera in Auto ISO mode, it is one more dimension the camera can use to get a usable image. But be aware that you pay a price for using high ISO values: grain. There is no free lunch in photography.
RAW format is a way of storing information about an image so that it gets as close as practically possible to what the camera sensor recorded.
It is not about resolution. The resolution of the image is (unless cropping) determined by the resolution of the sensor. You can have two images in different formats (say JPG and RAW) and they hold the same resolution, but what is different is how much information is stored about each point or dot (pixel) in the image.
RAW format stores much more information about each pixel than other formats do. This maximizes the options for you to work with the image in post processing – you can recover shades in the dark, clipping in the highlights and work with the colors to a degree that no other format allows you to.
But there is no free lunch in photography. The price you pay for all this flexibility and headroom is the file size. RAW format takes up much more space than JPG or HEIC formats, even when the resolution of the image is the same. That is why many edit their images in RAW format and finish their work by exporting the file to a format that takes up less space – this makes sharing on social media much easier.
I short introduction to MTF charts and how to read them. Deliberately made not-too-technical.
A MTF (Modulation Transfer Function) chart gives information about how a given lens performs when it comes to sharpness and contrast.
Indication, nothing more
It is by no means a perfect tool, but it does give some information that can be useful when you are in the process of selecting your next lens. There are many reasons why the MTF chart is not perfect, but here are some:
For zoom lenses these are only tested at the wide and long end – how the lens performs in between is often not defined.
Some lens manufacturer like Nikon only give data for the lens wide open. How the lens performs stopped down is not shown (Canon does better here). Compare of lenses with different speeds is hence not on a “level playing field”.
The test is done on a lab lens with a close-to-perfect copy of the lens. However, during production, there will be sample variations between lenses and hence your copy may perform slightly different from what the MTF chart shows.
Manufacturers do not test the MTF charts the same way, so you can only (meaningful) compare MTF charts from the same manufacturer.
Lens performance is also a function of which camera the lens co-operates with. The MTF chart are produced in a camera agnostic way, so the performance of the lens tested and your specific camera may vary relative to the MTF chart
So, please, take the MTF charts as an indicator and not the entire truth!
The MTF chart
There are some technical aspects of the MTF chart that I will not cover here as it gets too technical for me and I also fear that we loose sight of the bigger picture. What I want to cover here is how to read the chart:
Chart from the Nikon home page. The 50mm 1-8G lens.
The x-axis on the chart is the distance from the center of the lens. All the way to the left is the center point and going right it moves further and further away from the center. The point here is to test how the lens performs in the corners, which traditionally is the weak point for lenses.
Lets say the y-axis is an indication of how the lens performs (this is not the real story, but sufficient to read the graph). A value of zero is super poor performance, a value of one (1) is perfect performance. A perfect lens would hence have a flat curve going straight from left to right with all values on the y-axis reading 1. Or, as Nikon coins it: the higher and straighter is better.
The two colors show the sharpness (blue) and the contrast (red) respectively.
Contrast, red: In the graph above the contrast is very good in the center of the lens, it stays good to around 17-18 mm from the center of the lens and then it drops.
Sharpness, blue: The sharpness is really good in the center and then falls with an almost constant slope moving away from the center. The corner sharpness does not appear to be impressive.
Mind you that this is only a graph for the lens at full throttle (f=1.8) – you can see in the bottom right of the graph that Nikon has made a note to make us aware of this. The lens probably performs much better stopped down, but we get no wiser in this regard studying the graph, unfortunately.
You will also notice that there are two lines for both sharpness and contrast, a solid and a dotted. When they test the lens, they do so with small lines drawn very close to each other. The direction of these lines varies between the solid and the dotted graph. The point when it comes to reading the graph lines is that the closer they stay together the better the lens performs. You cans see that the blue lines indicating sharpness stays well together almost to the edge of the lens, whereas the contrast lines drift apart when moving towards the edge of the lens (some types of aberrations start to surface for example).
Even though Nikon says that higher and straighter is better, a good question is: What does good looks like? How high in the graph do you need to be in order to have a good lens? I think you get a feel for this when you have compared charts from a few lenses, but as a rule of thumb I think of anything above 0.8 as stellar, 0.6 to 0.8 as really good and anything below that as “I need to think about this before buying”.
Mind you that no lens is perfect, so you will never get a straight line in the graph. But some do come close. Take a look at the f/1.8 50mm prime from Nikon for the Z-mount. What a lens! I think it makes sense to compare it to the graph above as it is same manufacturer, same focal length, both primes and equally fast (f= 1.8). I have no doubt that this lens technically a much better performer. I do say “technically” because some absolutely love the look of a Nikkor vintage lens, but then again I would assume they do not study MTF charts!
I hope this gave you a good introduction to what an MTF chart is and how to read it. Questions and comments are of course more than welcome.
A short post about what exposure compensation is and how you use it.
When your camera calculates the correct exposure in the automated or semi-automated exposure modes, the camera sets the shutter speed and aperture to achieve a technically correct exposed picture.
Exposure compensation is simply that you ask the camera – on top of the calculated exposure – to deviate from that exposure as per the exposure compensation settings. So if you dial in a exposure compensation of say -1 stop, then the resulting image will be slightly under exposed.
Dials
The exposure compensation dial in the Fuji X-T20 ranging from 3 stops over exposed to 3 stops under exposed and all in between in 1/3rd stops
The image above shows the Fuji X-T20 exposure compensation dial where you simply turn the dial to the desired compensation. A more traditional implementation is a little push button on top of the camera with a +/- sign. When you hold down this button and at the same time turn the command dial, you can set the exposure compensation value. The top LCD will typically show you the values while you push the +/- button.
The exposure compensation button on the Nikon D4. The Nikon D700, D750 and Z50 has exactly the same implementation.
Use
You can use this a as a creative tool, where you systematically over or underexpose your images (low key and high key) to achieve a creative effect. Or you can use this to compensate for the automated exposure when you know your camera will get it wrong – for example shooting portraits in the snow, where your camera will have a tendency to under expose in attempt factor in all the white in the frame.
If you shoot in RAW format, then a lot of tweaking to the exposure can be done in post processing as the RAW format give a lot of headroom for adjusting the exposure. However, many prefer to get the exposure right “in camera” to simplify their workflow and save time.
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.
A histogram on my Fuji X-T20 rear LCD
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).
“Lefty”
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.
Ever since the film days, SLR (Single lens reflect) cameras were built with a mirror behind the lens, that sends the light from the lens up into a pentaprism, that passes the light on to the viewfinder for the photographer to see. When the shutter is pressed, the mirror flicks up, exposing the film or the sensor behind it and the content captured will be the same as what the photographer could see in the viewfinder. During this process, the viewfinder turns black as the mirror blocks the light.
The traditional travel of light in a SLR/DSLR: Through the lens, hits mirror, sent upwards in the pentaprism and finally through the viewfinder to the photographers eye.
With the introduction of Digital SLRs, the film was replaced by a sensor that not only can read the light in a fraction of a second, but actually can do so constantly, which opens up for shooting movies. Further, many DSLRs today are equipped with a large screen on the back to present menus and options for configuring the camera, plus previewing the pictures.
Live view combines the sensor and the LCD on the back of the camera, so that the camera continuously shows on the screen what the sensor receives. As the mirror, when it is down, blocks the light from the sensor, the DSLR will – when it is put in live view mode – flick the mirror away to allow the light continuously to flow to the sensor:
Live view mode. Rear screen shows what the sensor receives.
The camera will – subject to the processing capacity – try to make what is viewed on the screen as close to real time view as possible, but for older cameras you will notice a lag or a bit of delay in what is shown in the rear screen.
Rear screen on the Nikon D700.
Some cameras allow you to flip the screen upwards or downwards, and some are even fully articulating, allowing you to swing the screen 180 degrees around to be viewed from the front of the camera. Many vloggers use this feature to view themselves when recording video. The rear screen on the older Nikon D700 depicted above is fixed and cannot be moved at all.
So what is the point?
So other than this now being technically possible, what is the point with Live View, if any? I think there are several:
First of all, sometimes the optical viewfinder is hard to use, for example when you try to shoot in a very low or a very high angle. You may want to shoot over a crowd at a concert, or shoot very low to get a certain angle of view. In those cases it can be difficult to put your eye to the viewfinder, unless you either have brought along a ladder an/or want to crawl on the ground. Especially if your camera has a tilt screen, then you will love this feature, but even with a fixed screen the Live View is a big help.
Second, the fact that the rear screen is a processed version of what hits the sensor, it is possible to combine what the sensor sees with various electronic overlays like a large virtual horizon indicator. I use that a lot to secure that my landscape pictures are level. Another example is focus peak indicators, where the screen shows which parts of the picture is in focus – it can be in the shape of say red colored dots. This is a great aid in obtaining focus when shooting with a lens without autofocus. A third example is to show picture in picture, i.e. the normal picture and then a smaller frame inside the picture where a zoomed in version of the picture is shown, again to aid focus.
Third, maybe a variation of the second, is that you can zoom in on the picture in the rear screen. Again this feature is super useful if you shoot with a manual focus lens and want to zoom in to make sure you have nailed focus.
A fourth benefit of Live View is that the camera typically does not use the dedicated focus system, but instead used the sensor and a bit of processing power to obtain focus. As many elder cameras have the focus points only in the center of the frame, you cannot obtain focus say in the corners. With Live View this limitation is gone and for single point focus you can use all of the frame to select your focus point. Especially macro photography shooters with elder cameras use this feature a lot.
Finally, when shooting into the sun, the light that you see on the rear screen is a processed version of reality and I doubt that the LCD screen is so powerful that it can blindfold you. When shooting into the sun using the optical viewfinder, I often find that I am blindfolded temporarily when staring straight into the sun. So I often turn to Live View in those cases. Notice that many camera manufacturers warn against shooting into the sun, both in Live View and using the optical viewfinder, so please consult the manual for your camera beforehand.
Any downsides?
The rear screen requires power to operate, and a lot more than the optical viewfinder where that part of the process is purely mechanical. So you will find that your batteries will be eaten faster than when shooting using the optical viewfinder.
For elder cameras, you may find that live view is sloooow. Very slow. It takes ages from you hit the shutter to the picture is done. On my Nikon D700 for example, the focus part alone takes several seconds (when in Tripod mode), where it for later models (the D750 for example) is much better.
And finally sunshine is not your friend if you shoot outside on a sunny day. It is like watching TV outside. It can be difficult to see the screen.
Thank you
Thank you for reading this far. Comments, questions and suggestions are more than welcome!
Credits
Illustrations used:
User: Kolossos – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=925806
