Category: Photography Tips & Techniques

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Quality criteria for lenses

Quality criteria for lenses

How do you find the perfect lens? To be honest: I have no answer to that. But I can show you how to find the right lens. I have a couple of criteria that are crucial for this.

Quality of the lens

With lenses, of course, the first impression counts. What material was used for the lens? There are lenses that are made from 100% plastic; even the glasses. Now it depends on your requirements. It is not bad to use a cheap lens, but if you want to take photos in the rainforest, I would advise against such a lens.

For beginners, I recommend a cheap zoom lens or a fixed focal length. If you are in the advanced field or even in the professional field, you should rely on first-class workmanship and weatherproof lenses, especially when it comes to sharpness and strong weather influences.

Most manufacturers have special series for this, such as the Sigma ART series, the Canon L series or the Nikon series with the golden ring on the lens. These are built in such a way that they can withstand dust, dirt, moisture and temperature fluctuations much better.

Focal length

The focal length is not decisive for the quality of a lens, but you should definitely include it when planning your lens purchase. This should match the area and the way you are photographing. There is no point in buying a lens that covers every focal length . On the one hand it makes a lazy photographer and on the other hand the quality drops. If the lens can cover a larger focal length range, you usually have a dull picture and a lower light intensity.

Extreme focal lengths also have an impact on quality. If the focal length is in the extreme wide-angle or telephoto range, the lenses are often very expensive or quality losses can be expected. This can be blurring or distortion.

Light intensity or maximum aperture

The light intensity is decisive for many when it comes to lenses. With a high light intensity, you can open the aperture wider and get significantly more light on the image sensor. This makes it possible to take pictures in dark light situations without increasing the ISO value .

So if you often take photos in such situations or if you have a blurry background (i.e. you need a shallow depth of field) you should pay attention to an appropriate aperture .

The aperture can be opened much wider, especially with fixed focal lengths . With zoom lenses, a corresponding revelation is usually associated with a higher price.

Sharpness

From my point of view, this is extremely important. If the lens is sharp, you get completely different images. This cannot really be copied with image processing.

With different glasses and significantly better processing, a completely different sharpness and a completely different contrast can be achieved.

I can promise you that here, of course, but what do you think if I just show you. The following images are both unprocessed and not sharpened. One was made with a € 100 prime lens and the other was made with a € 750 prime lens.

Optical resolution

Let me elaborate on the previous part. Because what we perceive as sharpness is called optical resolution. This optical resolution indicates how many lines the lens can display. It’s kind of like an eye test at an ophthalmologist. The finer the lines that can be displayed, the higher the optical resolution.

I have the following opinion on this: The lens should match the camera. It is much more beneficial to use a high-quality lens on a cheap camera than the other way around. Sure, 50 megapixels sound great in a camera, but if the lens can’t reproduce it, they won’t do anything. The many pixels on your camera are then just mud.

But don’t just rely on laboratory tests. Try lenses for yourself.

Bokeh

Bokeh not always back. Anyone who thinks that this is just a blurry background will quickly be taught better. Because depending on the lens, you get a completely different blur in the background. But let me show you more in the following example.

In this picture you can see the 50mm 1.8 from Canon and the 50mm 1.2 from Canon. Both set to f / 1.8. If you pay close attention, you will see that the 50mm 1.2 has a much softer background. Of course there is about 1000 € between the two lenses, but I wanted to demonstrate that you get a completely different bokeh .

If you can’t really see that difference now, then you don’t really need to worry about a more expensive lens. At least as far as the bokeh is concerned 😉

Close focus limit

This is interesting for all macro photographers.

Every lens has a close focus limit. This unit describes the minimum distance between the subject and the image sensor. If the subject is closer to the sensor, the lens can no longer focus and the image becomes blurred. Incidentally, it does not matter whether you focus manually or automatically.

So if you like to get close to your subject, you should pay attention to this value and combine it with the correct focal length . A minimum distance of 2.2 meters sounds a lot, unless you use a focal length of 600mm. It all depends on the right combination.

Autofocus

Auto focus is very important with a lens. Of course, otherwise, all images would be out of focus, but what exactly makes a good autofocus?

Speed

Faster is better? In any case, it should also be precise. It’s not just up to the camera how fast your autofocus is, the lens also has a part in it. Because the glass elements in a lens have to be moved in order to change the focus. A more powerful engine or a more sophisticated system can change a lot here and be decisive for a sharp photo.

Precision

What good is a great lens if it is often wrong? Well, it’s not normal for lenses to be wrong, but there’s a moment when they do. This is due to the back or front focus. With DSLR cameras, this is to blame for the fact that your subject can be blurred. This can often be adjusted with cameras, but it is laborious and not possible with every camera model.

Balance front or back focus

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Incidentally, this problem does not exist with DSLM cameras. Due to their design, these are not prone to this error.

But why am I addressing this topic? With third-party manufacturers in particular, it can often happen that the focus is far off. This became known especially at Sigma with the 35mm 1.4. This lens is only half the price of the Canon original, but many have complained that the autofocus failed and went wrong far too often. Once calibrated and the lens is just awesome…

Noise

Probably less important for most people, but if you want to film or take photos in an environment in which you should avoid loud noises, this point is important. I recommend an ultrasonic motor  here. This technology ensures almost silent focusing.

Image stabilizer

The image stabilizer is a great tool that offers great support, especially in low light or high focal lengths. But it is not only there to avoid blurring with the free hand, but also to be able to expose longer. You may still remember the rule of thumb from the exposure time . If we apply this, we can only expose for a certain time. What if we want to expose longer? Then an image stabilizer can help 🙂

A good image stabilizer can give you a buffer of 2, 3 or even 4 f-stops in exposure time . If we apply the reciprocal shutter speed rule, in which the exposure time corresponds at least to the focal length , we come to the following result.

Focal lengthmin. timeStabi 2 panelsStabi 4 panels
25mm1/251/81/2
100mm1/1001/251/6
200mm1/2001/501/13
400mm1/4001/1001/25

So if you often shoot in situations where you are photographing still subjects on your free hand, you should definitely consider using an image stabilizer. It is helpful in many other situations as well. You will almost always benefit from an image stabilizer and if not, it can simply be switched off 😉

Distortion

Most lens distortion occurs in the wide-angle range. Then the edges of the picture are shown distorted and your motifs are unreal. If you like to photograph architecture, that’s something extremely annoying and the photo quickly looks unprofessional and ugly.

Even if these errors can often be corrected easily in image processing, it doesn’t do any harm to have a lens that does not allow such errors in the first place. Above a certain price range, the distortion becomes less and less and sometimes disappears completely. But remember: The whole thing is based on physics. This can only be tricked to a certain extent. This means that from a certain focal length it does not matter how expensive your lens is, such distortions occur.

The extreme example with an 11mm fisheye lens

Vignetting

In addition to the optical distortion, it can happen with lenses that the edges of the image are darkened or blurred. The darkening is something that I actually really like. In portrait photography in particular, this effect ensures that the viewer’s gaze focuses more on the center of the picture and the subject. If you want to place the motif in a different place, that is again unfavorable. However, at least the dark edges of the image can be easily removed in image processing.

Stray light

Have you ever photographed in the sun with your mobile phone and the picture was simply outshone and nothing really visible? That’s a different matter with high-quality lenses. Extreme light situations and backlighting in particular ensure significantly less reflection and a natural contrast with the appropriate compensation and value .

Chromatic aberration

Chromatic aberration is a color fringing that can appear on contours. But don’t worry, you can get a grip on this quite easily in image processing.

Now what’s a good lens?

Unfortunately, I can’t tell you that, because this feeling is completely subjective. Everyone has different demands on their lenses and different ideas about a good lens. However, I have a few tips on how to use the previous points to find exactly what you are looking for. Even if the last points sounded like everything could easily be corrected while editing, it is definitely not so. A good lens can make a difference like day and night. You don’t believe me

Borrow lenses before you buy them!

Borrow a lens before you buy it. But not just any run-of-the-mill lens. Also take a high quality one. My world and my understanding of good pictures changed completely when I tested the Canon 50mm 1.2. I didn’t buy it and went for a Sigma lens, but it’s worth it just to find out what’s possible.

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The aperture in photography

One of the most important factors in photography is the aperture . The aperture is a lamellar opening in the lens that opens and closes. It has two influences on a photo. On the one hand, it controls the brightness and, on the other hand, the depth of field (or depth of field).

General information about the aperture

Surely you know the portraits or macro shots where only a small part of the picture is sharp. The rest disappears in a blur. With this type of image we speak of a shallow depth of field. We sometimes control the size of this area through the aperture and have different areas of application for this. In landscape photography, we want to be as sharp as possible. But for this it is not necessary to close the shutter as far as it will go! Depending on the lens and camera, aperture values ​​of 5.6 or higher are enough to speak of a high depth of field. The opposite are low aperture values. These open the aperture further and ensure a low focus range.

Aperture value

The aperture value is a little bit confusing, because with a higher value we have a closed aperture and with a lower value we have an open one. This is because the aperture value is a fraction. We don’t actually set an aperture of 4, but an aperture of f / 4. This is because the aperture value is calculated from the focal length of the lens and the diameter of the light passage. This explains why lenses are sometimes very thick, but is difficult to remember for beginners.

Aperture step

If that wasn’t too much for you, I have another tip for you. Because we have a certain approach to the aperture values. As you may have already noticed, you cannot set an aperture of 3.8 on your camera ; an aperture of 4 works though … Why?

It has to do with a very simple calculation and logic. If the aperture makes a full step (from 5.6 to 8, for example), only half as much light falls into the camera. Conversely, of course, from f / 4 to f / 2.8 we let twice as much light into the camera. In this case one speaks of an aperture step. This is available in whole steps and in thirds.

Whole aperture steps:

1 – 1.4 – 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16 – 22

In order to be able to adjust the aperture more finely, there are now third steps. These can be found in most cameras between all the steps for the blind. ( 2 – 2.2 – 2.5 – 2.8 ). Many values ​​in photography are based on this aperture value; also the exposure time and the ISO value.

In simple terms, however, you can say that if you turn a setting wheel on the camera three steps in a certain direction, you have halved or doubled the amount of light. Depending on which direction.

The focus range

The area of ​​focus is the area in an image that is in focus. The size of the focus area is controlled, among other things, by the opening of the aperture . If you keep it open, the area of ​​focus will get smaller, and if you close it it will get bigger.

With the autofocus, you can control at which point the image is in focus, through the aperture how far this focus spreads to the front or back. Please note that this focus area spreads on the camera axis. Everything that is left or right of your subject can therefore also be sharp.

Take pictures with the aperture open

There are several advantages to opening the bezel . In this way, you can keep the focus area in your photo small, which makes for a wonderfully focused look in portrait photography or macro photography.

Take pictures with the aperture closed

The complete opposite is of course the closed aperture . The closed aperture ensures that the picture is naturally darker. Less light comes into the camera, so the picture becomes darker. This can be an advantage if we want to expose longer or if we need a large focus area.

Closing the aperture (f / 5.6 -> f / 8 or smaller) increases the focus area . This is great for group pictures or landscape shots, because at this moment we want everything to be sharp. To do this, it is not necessary to close the aperture to f / 22, i.e. as far as it will go. In most cases an aperture of 5.6 is sufficient. That depends on other influences on the sharpness range. I’ll explain this to you now.

Further influence on the focus range

The focus area depends on the distance to the subject and the focal length used . If you take photos at a wide angle, the field of focus (also depth of field) is significantly larger than with a telephoto lens at the same distance.

An example with aperture 2 and a distance of 4 meters:

  • 17mm = 20.92m depth of field
  • 50mm = 0.77m depth of field
  • 200mm = 0.05m depth of field

The distance to the subject has the same influence. Have you ever noticed that the distance to the subject changes the blurring in the background? With a lot of distance the focus area is quite large, with a short distance it becomes smaller and smaller.

Again the example with aperture 2 and a focal length of 50mm

  • 1 meter distance – 0.05m depth of field
  • 2 meters distance – 0.19 m depth of field
  • 5 meters distance – 1.21 m depth of field

So if you want to have blurring in the background of your portraits, you should not only choose an open aperture , but also get close to your subject (and keep a distance from the background).

The connection between all these influences and factors is certainly not easy to understand at the beginning, but over time this becomes easier and easier. With a little practice you will develop a feeling for which combination of aperture , distance and focal length is the right one for the respective situation.

Limits of the lens

You have already learned a lot about aperture and depth of field. As you have probably already noticed, not every lens can set every aperture . The reason for this is usually the zoom. The zoom requires space in the lens. Every moving part takes its toll and usually ensures this limit. This is why you can usually not open the aperture any further, but what is the solution?

Lenses with the largest open aperture are fixed focal lengths. A fixed focal length is a lens without zoom and usually creates f / 1.8 or even more open (f / 1.4 or f / 1.2). There are also zoom lenses that work in a similar field, but these are often very expensive. So if you want to work with a small depth of field, you should use a prime lens.

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The Digital single lens mirrorless camera (DSLM) purchase guide

The Digital single lens mirrorless camera (DSLM) purchase guide


The DSLM; for a couple of years it has been changing the photography market. What started out as a poor SLT attempt developed into a completely new and booming market? The market for DSLMs (D igital S ingle L ens M irrorless) or system cameras.

These are now available for every budget and many manufacturers now have a mirrorless camera in their portfolio. But should you buy a mirrorless camera? Does it have any advantages over DSLRs ? That and much more is the content of this page and finally I will show you a few models that I would recommend.

What is a system camera / DSLM?

There are two types of system cameras, with and without mirrors. The system cameras with mirrors are called SLRs and those without are called mirrorless. Sounds logical, doesn’t it? The mirror in the DSLR is historical and comes from a time without image sensors. The system has been perfected over decades. But for a few years now, DSLMs have been picking up. Teething problems are being eradicated more and more and many photographers are seeing a new alternative that offers many advantages over the old DSLR cameras.

The mirrorless camera / DSLM in detail

Height and weight

Many see an enormous advantage here. The DSLM lacks the mirror and as you can see in the example above, this saves space and of course weight. That is why the mirrorless cameras are much smaller and lighter. But they are still bound by certain limits. They are not as small as compact cameras. This is simply not possible with interchangeable lenses and large sensors. But they are still smaller than the DSLRs and therefore more mobile and inconspicuous.

Lenses

This is a special feature of DSLMs that you should definitely not forget. Other lens connections are used that allow smaller lenses, but they are not that small. There are certain limits that are physically given and specify a certain size. If you only buy these cameras because you want something as small and portable as possible, you should look around for a bridge or compact camera .

Ergonomics

Ergonomics is probably the first thing anyone who is switching from a DSLR to a DSLM should notice. The manufacturers try to make this as similar as possible, but it is simply a different feeling that can seem strange, especially with long-term DSLR users. In direct comparison to an SLR camera, I find the DSLMs to get used to at first. They are just small and lie better in the hand of one than the other. In my opinion, many manufacturers simply have too many buttons on the small housing, which makes operation a challenge.

There is only one option here: try it out. I recommend that anyway before you buy a new camera. DSLM cameras come in different forms. Very large, such as the Sony A3 or Canon EOS R, but also very small such as the Sony A6000 or Canon EOS M50. Depending on the model, you have an electronic viewfinder or just the display to look at your pictures. In any case, try out what suits you and what suits your type of photography.

Electronic viewfinder

A DSLM or system camera takes photos with an electronic viewfinder or the display. This means that the viewfinder does not have a direct optical connection to the subject like the DSLR, but a display. It is like looking at the finished image through the viewfinder.

The electronic viewfinder offers several advantages:

  • Image preview: You get a direct idea of ​​your photo and actually see the finished image before you press the shutter release. If you now change the settings on your camera: for example , closing the aperture or increasing the ISO value , the image changes immediately and you can judge whether you like the photo or not. You can also see the picture in the viewfinder after you’ve taken it. So it’s a second display that works just like your large camera display. The advantage, however, is that you can use it without being distracted by the sun.
  • Exposure aids: Because our EVF is a display, we can use many aids that the optical viewfinder cannot offer us. We can show a histogram , use an overexposure warning and much more … You can see immediately if your camera is not doing something the way you want.
  • Manual focus: With manual focus, we can use the focus peaking to see where our focus is and even zoom into the image. A real help for manual focusing.
  • Much more: Since you can show almost everything in the displays, there are no limits to the manufacturers. Water cars, grids for image creation, image styles and much more is possible.

Now I’ve written so many great things about the electronic viewfinder that I would of course like to point out a few negative points. Because the electronic viewfinder naturally always has to be supplied with power. This should not be ignored with some models and some cameras have extreme problems with high power consumption and thus a short battery life. Also, for many photographers it is not pleasant to constantly look at a display (myself included). It’s a completely different feeling to actually see the subject instead of just being shown it. The cameras are getting better and better here, but sometimes they are lagging behind due to delayed display (the display is delayed compared to reality).

I would like to add one point for those who like to take photos at night (long exposure ). If you take a picture with the DSLR, you have the light intensity of your own eye available. With the DSLM, the display in the viewfinder depends on the power of the camera. That may not sound too bad, but there are a few moments when I would have wished for my DSLR…

If you are not sure which viewfinder is right for you, I recommend that you test both of them once and take a closer look. I find the DSLR to be much more pleasant, especially in series pictures and when photographing fast subjects, but something different suits everyone.

Autofocus

There are several options when focusing with a mirrorless camera (DSLM). You may be familiar with the first option from the DSLR. If you switch to live view here (i.e. using the display), the autofocus becomes significantly slower. This is because the camera is using the contrast AF. This simply shifts the focus until the image has the highest possible contrast has. This is very precise, but unfortunately a lot of time is lost in trying out and “pumping” the focus. That’s why there is still phase autofocus, which was reserved for DSLRs for a long time. Here, two sensors compare the light (phase) falling into the lens from different angles and thus know from the first measurement what needs to be changed on the lens to focus. Cool right?

Most modern DSLM cameras use a combination of these two methods in order to be able to focus both quickly and precisely. If you use a modern DSLM camera, you should make sure that it supports phase or hybrid autofocus.

Picture quality

We come to the last point, and in my opinion the most important point. The image quality. In terms of image quality, the system camera is in no way inferior to the SLR. Of course, not all cameras are the same here, but in most cases you don’t have to worry that you have something worse just because you are using a different system. Most cameras even have the same image sensors installed (Sony makes sensors for some Nikon cameras and Canon has installed the same sensor in the 5D4 & R and the 6D2 & Rp). There is only one real way you can be sure that the quality will meet your expectations. Test the camera 🙂

Choice of lenses

From my point of view, this is a major negative point. It is not the case with all manufacturers that the newer the manufacturer is in the DSLM market, the more likely it is that the choice of lenses is limited. For decades it took a long time to develop a wide variety of lenses for DSLR cameras. This has only just begun with DSLMs and although lenses are already on the market, one only starts with the most important ones at the beginning. One or the other special lens may not be found here yet. Of course there are adapters that allow the use of DSLR lenses, but I have made the experience that it often leads to problems (slow autofocus etc.).

There are always new lenses on the market, but keep in mind that you may not find everything here and that you have to expect limitations.

Is the mirrorless camera or system camera right for you?

This is of course a question that cannot be answered easily. I always recommend trying out the camera beforehand. But I would like to give you a little support along the way that should help you with your decision.

The DSLM is interesting for you if the following points apply:

  • You’re used to smaller cameras – that  was the first thing I didn’t like about the DSLM cameras. The size. Ok, I also come from the DSLR segment and am used to large cameras with battery handles. However, if you’ve been taking photos with a compact camera or mobile phone the whole time, then the size of the DSLM is perfect for you.
  • You can handle the digital viewfinder – the electronic viewfinder is not for everyone. Some have problems seeing everything on a display / digital viewfinder. If that is not a problem for you, then you can use the mirrorless camera.
  • You want to try something new – that was one of the reasons why I keep getting a DSLM for different jobs. It’s just fun to use a different camera. Maybe it fits better than the current one? Just keep in mind that you don’t need a new camera straight away because it can do one thing a little better than the current one.
  • Video – Yes, the site is actually called Learn Photography, but especially when it comes to video I would prefer the DSLM to the DSLR and any other camera. They’re small, they’re incredibly powerful, and you can’t beat the autofocus when filming.

Buy recommendations

Entry level DSLM

Canon EOS M50 * – Sony Alpha 5000 * – Olympus PEN E-PL9 * – Panasonic LUMIX G *

Advanced DSLM

Sony Alpha 6300 * – Olympus OM-D E-M10 Mark II *

Professional DSLM with full format sensor

Canon EOS R * – Nikon Z6 * – Sony A7 III *

Otherwise, make sure that you try your camera before buying and that you do not justify the purchase with the one feature that the new camera can do better. You take the photos and not your camera 🙂