How to shoot pinhole photography

No lens!

Pinhole photography is simply that you take the lens off your DSLR or mirrorless camera, and instead block the light from entering where the lens would be mounted, except for a tiny, tiny hole where the light can seep through is very limited amounts.

But why?

Pinhole photography is a nerdy discipline in photography, and certainly not for everyone. It requires long exposures and the images are -due to diffraction – not particularly sharp. But it is a more engaging type of photography, where you will need to spend more time with your camera and you will feel more engaged in the process of shooting, relative to the point-and-shoot like style that most of know from our smartphones..

How?

You need a camera where it is possible to take the lens off. This can be a DSLR or a ML camera, but if you can choose, I would recommend a DSLR, as the sensor is bit better protected behind the mirror than what is the case for a ML camera. You are walking around with a camera with a hole in it after all!

A small hole drilled in the lid used to seal the camera when no lens is mounted.

There are a few different ways you can do this, but I prefer to take the lid you use to seal off the camera when no lens is mounted, and drill a small hole in the centre of the lid. This gives a relatively robust solution, should something hit the area where the lens is usually mounted.

A piece of tinfoil taped to the lid. and a small hole punched in the tinfoil.

Make sure the hole is free from any fragments from the drilling process, so the hole is clean and round. Next, mount a piece of tinfoil on the lid, using a bit of tape. Smart people use tape that is not transparent – from the image above you can see that I am not in that group! And finally, you simply need to take a needle and punch a hole in the tinfoil.

If you want to be very serious about it, you can take a black permanent marker and color the tinfoil black on the side that faces the camera. This way, you minimize reflections on the “inside” of the tinfoil. Needless to say, you need to do this before taping the tinfoil to the lid.

After that, it is simply a question of mounting the lid on the camera, and you are all set! One small thing missing: blocking the viewfinder!

The viewfinder on the Nikon D4 can be blocked by moving a switch to the left of the viewfinder. Here it is closed – no light will enter!

When you are shooting with long exposures, so called false light can enter the camera via the viewfinder, so you need to block it. On some cameras it can be done by flipping a switch next to the viewfinder, if that is not the case for your camera, then you need to block it manually – but please don’t use chewing gum! Yes, seriously, I have seen some photographers do that!

A tripod is (almost) mandatory

Not everyone likes a tripod, but it is necessary to hold the camera still during long exposures. If you don’t have a tripod, try putting the camera on a big stone or a solid fence or whatever is available to you, to secure the camera is still during the exposure.

In my experience, the exposure times for a small pinhole is something along these lines:

  • Shooting into the sun: 10 seconds
  • Shooting on an overcast day: 20-30 seconds
  • Shooting at dusk: around 2 minutes
  • Shooting at night: 4+ minutes

I always try to shoot at base ISO, typically 100, but it may vary subject to your camera. If you shoot at higher ISO, the result may be noisy. I will say though that shooting at night will require so long exposures that in those cases I shoot at ISO 400 or 800 simply because my patience does not suffice. But as a general rule, stay at base ISO.

The auto white balance (WB) will struggle to read the light as there is so little of it, and it may be a good idea to set the WB manually. If you shoot RAW, then you can fix this in post, but I try to get my images right in camera as much as possible, and if you like that as well, the manual WB is the way to go.

As there is no lens mounted, you don’t have to worry about the aperture! My guess is that you are shooting at around f/200 – you can do a lot of math to figure this out; I don’t really care. I don’t need to know the exact aperture, and I simply take a few test shots to figure out what a reasonably right exposure time is.

Bulb may be required

It differs from camera to camera, but when you need your shutter to be open for a long time, the camera may not have a pre-defined option for say keeping the shutter open for 1 or 2 minutes. My Nikon D4 stops at 30 seconds, after that, I need to use bulb mode. That means holding down the shutter while the exposure is going on, which I find to be a pain.

A cabled remote release for the Nikon D4.

So I have bought a remote release, that gives me more options for long exposures than what the camera does.

If you don’t have a remote release or don’t want one, a workaround is to use multiple exposures. Say you ask your camera to expose the same image 5 times. And you set it up to expose each image for 20 seconds. Then the totality of that is a 100 seconds exposure. Only downside is that you will need to hit the shutter 5 times, but it is better than holding it down for 100 seconds, if you ask me.

Is it for you?

In pinhole photography, you are running around with a camera with a hole in it, and that is an invite for dust and dirt to enter. So if you don’t like to clean your sensor, then you probably wanna stay clear of pinhole photography.

Pinhole photography is for long exposures. You cannot shoot anything that moves fast like a cat or a bird in flight. It is mainly for landscapes and stilleben and that kind of images.

Woodland. Notice the almost infinite DOF and that nothing is particularly sharp.

But it is a very engaging style of shooting, you cannot see in the viewfinder what the camera will capture prior to hitting the shutter, so there is a bit of guessing and trial-and-error when it comes to pinhole photography. And that has a charm. But it may not charm everyone!

 

 

Which photography Youtube channels to follow?

Learning from YouTube

You can learn a lot about photography watching YouTube videos. But granted, the number of channels and number of videos is overwhelming and being new to photography it can be difficult to know where to start and what to prioritise. That is the aim of this post: to give you some anchor points regarding photography and YouTube. It is just my list, and I don’t claim it is fair or comprehensive – my hope is that you can use it as a starting point and grow your own list from there.

Daniel Norton – portraits and light

If there is one photographer that really knows about portrait photography and especially all aspects of lightning (flash, fill, etc), then it is Daniel Norton. When it comes to lighting, he is my guru. Period.

Daniel is a NY based photographer who has been a very successful photographer in the fashion industry, but now is more focused on teaching, both via his YouTube channel and his podcast over at Avoice. He also co-operates with Adorama, so often his videos are published under the Adorama brand, but you can also find videos that he publishes on his own channel. And of course he has both his own homepage and is on Instagram. His podcast is different from the videos in the sense that it “discuss what it means to be a creator in today’s content rich world” (quote from the podcast).

Marten Heilbron – reviews

Marten Heilbron is a YouTuber proving that to be successful you don’t need to be young and make fast paced videos, as long as your content is competent and relevant. And his channel certainly is. He describes his own channel as “detailed hands-on reviews, explanations and demonstrations of cameras. Here you will find honest and detailed camera reviews, along with some how-to videos and the occasional travel review.” – and it is a very precise description of his channel and its contribution. And then Marten always has that bit of humor and twinkle in the eye that adds an extra dimension to watching his videos. So look no further if you want a camera review and a camera demonstration in one go.

Tech Gear Talk

If you want to watch some of the best produced and most “delicious” reviews on Youtube, the channel Tech Gear Talk is worth a visit. He reviews a lot of non-photography items as well, such as smartphones and the like, so the channel is wider than “just” photography gear. His motto is “Buy it Nice or Buy it Twice” and it may not always be good for your wallet, but he certainly has a point!

Kai W – reviews

The reviews from Kai W almost could not be further away from the ones Marten Heilbron gives. Kais’s videos are made by the same small team and have a crazy or desperate angle, as if he really really does not want to do the reviews at all. I get the impression that he finds it a bit boring and therefore he tries to escape out of the traditional frames for review videos using crazy ideas or storylines in the videos. I often find that his conclusions (the last 20-30 seconds of the video) is where he gets serious. So pay attention to the very last words in his videos – this is where the good and serious assess-ment of the gear under review is to be found.

Steve Perry – wildlife

If you want to know a thing or two about both wildlife photography and how to make the most of your Nikon camera, look no further than to Steve Perry’ channel. He talks fast and his videos are packed with information, but always relevant and based on facts and experience. And what I really like: he often presents evidence rather than just making a claim.

Sean Tucker – creative process

If you are looking for lens and camera reviews, then the channel from Sean Tucker is NOT for you. He has a very different focus, more aimed at the process of being creative and why we do it. He does have some videos that address the “how-to”  side of photography, but he is never into the details of a certain camera or a certain lens; he’s channel is gear agnostic. His videos often start and ends with some very beautiful footage in slow motion with accompanying music, and in between he talks and debates on a certain subject. It is one of those channels that I return to again and again, maybe because I like the philosophical aura that seeps through each well made video.

Jamie Windsor – history

Jamie’s channel may to some be a bit in the same league as Sean Tucker, but I find him slightly less philosophical and a bit more towards the “how-to” side of photography. What I really like about his channel is that you can tell he has years and years of experience and he happily shares this with his viewers. Also, he often tells the story or the history behind a certain concept or hot topic.

Christopher Frost – Lenses

If you want a short focused lens review, this is the channel to go to. Christopher has specialized in lens reviews and often uses the same “template” for the videos so you know what to expect and secures that all the vitals are covered. And he has a calm voice and well paced way of presenting the lenses and their performance, which makes the videos a pleasure to watch relative to some of the more “noisy” channels.

Mike Browne – Learning photography

If you want to learn photography from a guy who you can tell loves to teach and share knowledge, then look no further than Mike Browne. This is probably one of the channels where I have learned the most about photography and basic concepts such as aperture and dept-of-field and how that impacts your images. If you listen carefully, you will find that he not only addresses the “how-to” part but also often talks about how to get “in the zone” of seeing great images long before you lift the camera.

Omar Gonzales – Fuji and entertainment

If you want to have a laugh and be entertained while still learning a lot about especially Fuji, look no further than the brilliant channel from Omar Gonzales. If you want to know him a bit better, paying a visit to his homepage is a way to do it. He claims to be camera agnostic, but I learned a lot about especially Fuji cameras and lenses from watching his videos. He is not a full time youtuber but has a portrait and event business.

James Popsys – Entertaining learning

James Popsys has a special relationship with sheep and that is one major reason to watch his channel! Another is that you learn a lot about photography and he has a great sense of humor and irony that makes watching his videos a true pleasure. And he puts a lot of thinking and perspective into his videos that you do not find with many other channels.

 

 

 

Review: Mastering composition – the definitive guide for photographers, by Richard Garvey-Williams

Definitive

The title of this book promises a “definitive” guide to composition. Googling the meaning of definitive, the first definition is “done or reached decisively and with authority” and one of the synonyms listed is “ultimate”. So this is the ultimate guide to composition. This author apparently does nothing to dim his shine!

Mastering composition – the definitive guide for photographers, by Richard Garvey-Williams

Comprehensive

This 175 page book is comprehensive, and covers all aspects of composition though 6 chapters. It is jam packed with illustrations – at least one per page and often 3-4 per page. As such the author walks the talk and shows how the theory presented can be applied in practice. The square format of the book works well to allow pictures and text to blend naturally.

The book covers so much more than the rule of thirds, e.g.: visual weight, framing, leading lines, dynamic tension, depth, color, tone, patterns and even a bit of gestalt theory! I find that it is one of the most comprehensive books I have found on the subject of composition. And then I really like that the author underlines that composition is a means to an end, and not an end in itself.

I did not find this book to be an easy read. At times, it felt like reading a dictionary, but I guess it is the flip side of being so comprehensive. So if you are searching for an entertaining book, you may need to look elsewhere – this one is serious about its subject and stays serious throughout.

Conclusion

If I was to recommend a book about composition for the notorious lonely island, it would be this one. It is not an easy read, and after the first read, I use it more and more to look up certain subjects, than reading it from start to finish all over. It works well also as a dictionary.

Some of the images have stuck with me in the back of my head and unconsciously influenced my photography and give inspiration for new aspirations. And as such, I have become a better photographer, processing and digesting the content of the book.  And that is probably the highest praise I can give to any book about photography, and as such this book comes highly recommended.

Related reading

Visual flow, mastering the art of composition, by Ian Plant w/George Stocking

 

 

Using a grey card and histogram to exposure correctly in Manual mode

Manual exposure

There can be many reasons why you want to control your exposure manually – the scene may contain a lot of bright or dark that confuses the automated metering system, you are shooting with flashes in manual mode or you just want to control the exposure because you like this way of working. Whatever the reason, there is a way to secure correct exposure using a grey card (18%) and the histogram in the camera.

Right in the middle

One of my flashes came with a grey card in credit card size. Actually it came with 3 cards, one white, one black and one grey. You only need the grey one, but just for the fun of it, I will use all 3 in the following.

The grey card to the left, the black card top and the white card right. The fact that the white card appears a bit grey would indicate that this image is slightly underexposed.

The grey card returns light in such a way that if your exposure is correct, then the grey card will produce a peak in the histogram right in the middle of the diagram. The histogram shows the distribution of light in the scene, with completely black areas to the left, completely white to the right and everything in between somewhere in the middle. The height of the graph shows the number of pixels in relation to the entire scene. So if you have a very dark scene, then the histogram is “lefty”, i.e. it looks like a mountain appears in the left side of the histogram whereas the right side is more flatland.

The simple idea is now that you take a test image of the scene, study the histogram and if it is off center, then you adjust the camera settings to make the grey card appear in the middle. If you are in Live View on your DSLR or have a mirrorless camera, you can actually see the histogram update real time as you adjust the camera settings, and hence no need to do a test shot unless you want to.

You adjust the camera settings meaning ISO, Aperture and Shutter speed. If shooting in manual mode is new to you, you can follow the link and see how it is done on a Nikon D750. The principles are much the same across different camera brands, and I think you can get the gist of it by reading the post in the link.

In the example above, you can see the 3 cards on a whit table and top right the histogram. Yes, it is a bit small, but you can see that there are 3 peaks – one the the very left originating from the black card, then the peak in the middle from the grey card and then the wider peak to the right, that is a combination of the white card AND the table behind the cards. This table is also white, but not as bright as the card. So the rightmost peak is also wider than the other two, as it is a combination of the table and the white card that span across a wider range.

In this example the grey card peak is not in the middle, but to slightly to the left, which is a sign of underexposure. Had it been to the right – then overexposure. So in this case the camera settings needs to be adjusted to let in more light, say leaving the shutter open for longer time or opening up the aperture. After the adjustment, a new test shot is needed to see if the desired effect has set in. If not, then redo until the grey peak is right in the middle.

So this is really all there is to it. Given that the ambient light does not change or the flash settings remain constant, you can now shoot a series of images without worrying about the exposure settings on your camera. I find this super useful for product shoots and indoor portrait shoots.

Related reading

What is manual focus in photography?

What is EV? And what is a stop of light?

High dynamic range shooting with a DSLR

Nightclub photography

So I got a question on YouTube related to nightclub photography and how that can be achieved.  In order to answer, I will start with the human eye, which has a dynamic range of 21 stops! Even the best cameras ever made can keep up with this performance – for example the acclaimed Nikon D700 “only” has a dynamic range of 13.9 stops according to DXOmark, whereas the very best modern cameras manage to go to 15 stops.

The dynamic range is the ability to distinguish between light intensity in the darkest of the dark and the brightest of the bright at the same time. The fact that it is at the same time is important. You can always underexpose an mage to make sure you preserve the details in the brightest of bright areas. And the other way around, you can always preserve the details in the darkest areas by overexposing the image. But the challenge is to do both at the same time.

A nightclub with both neon lights (super bright), disco light (bright and moving fast) and also dark areas (could be the dancing floor itself or the side of the bar) has an extremely high dynamic range. It is very similar to shooting the moon at night – you both have something very bright and something very dark at the same time. It is like shooting a 100 watts light bulb in a dark room at night.

Metering

Your metering system is likely to very confused if you shoot at a nightclub, especially if you meter with an average method. 95% of the frame is likely to be pitch black, whereas the remaining 5% is super bright. My guess is that your camera, unless you try spot metering or go to manual exposure, will over expose the image to compensate for the dominating dark. Try to experiment with different metering modes or manual exposure to get the exposure as you want it. You can also give exposure compensation a try.

ISO or not

A camera that can go to crazy high ISO values will not help you. Setting ISO high enables you to capture images where there is little light, buy when doing so, the parts where there is light will be over exposed. In other words, you will loose details in the bright areas. Here I ignore the issues related to high ISO such as grain and noise, the point is that even if you can live with these issues, it will not help you much.

Fast lens

A fast lens has the same features as high ISO, but without the grain and the noise. It will take in more light and enable you to shoot at faster shutter speeds all things being equal, but you will have the same issue as with ISO, that it will only push your histogram to the right and you need it to be extended in both sides.

HDR

High Dynamic Range or HDR you probably know from your smartphone. It offers the HDR feature without telling you what it does – it is an integral service that just presents you with the result. But behind the scenes the smartphones takes a series of images, typically some over exposed and others over exposed, and combine them into one picture selecting the correct exposed parts from the different pictures into one. You can do HDR with your DSLR and combine the images in post processing, and this will certainly work. The problem is just that your subject has to stand still while this happens. And disco lights have a tendency not to obey to this wish.

Loosing details

One of my favorite photographers is Sean Tucker. If you study his work, you will see that he often and deliberately looses details in the dark. His motto is to “preserve your highlights”, i.e. preserve the details in the highlights and let the different shades of grey be one big black surface without any detail.

You can loose details in both ends of the spectrum. Which “end” you choose is up to you. I would imagine that loosing details in a neon light would not matter much, suggesting that you should expose for the dark parts, i.e. over exposing to preserve details in the darker parts. But this is of course entirely up to you and what you want to express.

 

 

Review: Photography and the Art of Seeing by Freeman Patterson

The art of Seeing

Being a Canadian, Freeman Patterson is perhaps not so well known in Europe or the US as many other leading photographers. But if you look at his resume with a Lifetime Achievement Award from the North American Nature Photography Association and the Miller Brittan Award for Excellence in visual arts, then you start to understand the magnitude and importance of Patterson’s work.

Freeman Patterson: Photography and the art of seeing

Who is it for?

If you are new to photography and want to learn the basics, then this book is not for you. I would recommend that you instead look towards the books from Bryan F. Peterson or Joel Sartore.  The Art of Seeing is much more about the photography process and how you can widen your creativity.

What is it?

The book is organized around 3 main themes:

  • Learning to observe
  • Learning to imagine and
  • Learning to express.

Especially the last part, where Patterson talks about visual design, was a an eye opener for me. I have the same feeling when reading the book The Art of War by Lao Tzu, that even though I do not yet understand every sentence or every paragraph in the book, I have a very distinct feeling that it is a super condensed text that presents the essence of years and years of experience. I have read the book once, but want to read it several times to make sure I get all the points.

Can I recommend it?

Yes is the short answer. I have read many books about photography as this blog documents, and this is probably one of the best. The book has been developed to support a series of workshops that Patterson held way back when, but you can still make use of the exercises described in the book of you want to have the full benefit of the book. Even if you don’t do all the exercises or if you only want to read the theory, I find that this is an excellent book about the photography process and it comes with my highest recommendation.

Shopping link

Freeman Patterson, Photography and the Art of seeing

Video link

Related reading

Saul Leiter In My Room, Edited by Margit Erb and Robert Benton

Henri Cartier-Bresson Here and Now, by Clément Chéroux

 

 

 

Review: Photo Icons, 50 landmark photographs and their stories, by Hans-Michael Koetzle

400+ pages of iconic images

The title of the book as per the headline is a very precise description of what this book is all about. It “puts some of the most important photographic landmarks under the microscope” as it says on the cover. And very much so.

Photo icons, 50 landmark photographs and their stories, by Hans-Michael Koetzle.

The 50 images are presented and analyzed over the 400+ pages of the book, giving an average of 4 pages per iconic photograph. Enough to cover the basics and tell the story around each picture.

The table of content has an excellent overview with each picture in icon size and annotated with the relevant year and page to look up. The 50 images range from year 1827 to 2001. So you can quickly dive into the images of interest (I doubt you will read the book from front to back unless you are equally interested in each image).

Photographer Peter Leibings picture “Leap to Freedom” from 1961, just after the wall between East and West Berlin was in effect.

As I “cherry picked” the images of most interest, I have not read every single page in the book, but many of them, and I really enjoyed the “behind the scenes” view that you get to each image: What was the story, the photographer, what was going on in the world at the time the shot was taken, was it staged or candid, etc. Hans-Michael Koetzle really packs a lot of information into very few pages for each picture – it is a condensed read, but certainly worth the while.

So as a photographer it is not a book that will make you wiser in terms of photo technique (f/11 vs f/5.6), but it really documents how a photograph – even with all the videos and movies available today – can be powerful and influence what we remember and how we see history. And as such it for me adds a layer to my motivation to shoot the best pictures I possibly can.

Related reading

Understanding a photograph by John Berger

Review: Wild and Fearless by Uri Løvevild Golman

What a life!

When I started reading this book, my immediate reaction was: what a life this guy has had! And my next was: hmm, is my life a little boring perhaps?

The first 2/3rds of the book is a super entertaining and seemingly endless stream of adventures, beautiful women, new friendships, more adventures, great food and lots of alcohol! We follow Uri as he describes his life as a ski bum, bartender, a soldier in the Israeli army and travel adventurer.

Wild and Fearless by Uri Løvevild Golman – the epic life story of a National Geographic photographer

About 2/3rds the focus shifts towards Uri’s career as a wildlife photographer and how he and Helle (2nd wife) finally makes it as National Geographic Photographers. The adventures continues, but with Helle and photography in the center.

I must admit that I bought the book to see if I would be able to look over the shoulders of one of the greatest wildlife photographers of all times, but I was in that sense a bit disappointed. There is no description of f/8 versus f/11 or how Uri learned to photograph. Only his photography mentors are briefly mentioned. However, you do get to understand how much hard work there is in wildlife photography – one example is hiking 3 weeks in icy mountains only to come home with zero images of the snow leopard!

But I got something else: I got insight into a man with a mentality that very few posses.  At age 42 he was attacked and stabbed to a degree where most of us would have given up, and he was dead for several minutes before being revived. The attack left him injured with permanent disabilities as his brain was deprived oxygen for several minutes. He says towards the end of the book: “I have finally come to terms with the truth: I will never be able to walk freely again; no more hiking under the stars in the tundra or the forest. Nor will I be able to work my camera”. However, he refuses to take the role as a victim and he does not show any signs of feeling sorry for himself.

It is Uri’s hope that the book will give others inspiration to follow their hearts and dreams. Speaking for myself, I can say: mission accomplished.

I give this book my highest recommendations.

Related reading

WILD! What you love you will protect, by Helle and Uri Løvevild Golman

What is EV? And what is a stop of light?

Exposure language

EV is an abbreviation for exposure value. It is a way to express exposure in one number, i.e. the combination of shutter speed, aperture and ISO. To be quite honest, I doubt that many use EV’s today, as most rely on the exposure meter in their cameras, possibly in combination with the histograms.

But you can study EV as a way to understand exposure better. For example, if you shoot at f/4 and 1/125th, you are at EV 11, but if you open up the aperture to f/5.6 and maintain the shutter speed, you are now at EV 12. This is referred to as going one stop up.  So walking up and down the EV scale is referred to as stops of light. The light is doubled or halved for each stop. This gives you a “settings independent” way of talking about exposure, and you can say go one stop up in aperture and one down in shutter speed and arrive at the same EV.  So shooting at f/4 and 1/125th gives the same EV as shooting at f/5.6 and 1/60th. I half the light that comes though the lens (f/4 -> f/5.6) but double the exposure time (1/120th -> 1/60th). Both are EV 11.

For simplicity I have kept the ISO out of the description above, but it is the same logic: doubling of halving the ISO is the same as going one stop up or down in exposure. So the ISO scale is: 100 – 200 – 400 – 800 – 1600 etc. Many cameras allow you to select ISO values more granularly than full stops, and that can be handy, but remember to double/half to make a full stop difference.

Another area where EV is useful is when it comes to the spec list for a camera. The cameras dynamic range is expressed as an EV. For  example the Nikon D750 over at DxOMark is listed as having a dynamic range of 14.5 EV’s, whereas the Nikon D810/D850 has 14.8 EV’s. Higher is better, as it enables you in one shot to span across more difference in light in the scene, without blowing out the highlights or loosing details in the shadows. So if dynamic range is important for your kind of shooting, then the EV for a camera you consider buying  could prove an important part of your decision making.

Related reading

What is exposure compensation?

What are exposure metering modes?

What is a camera image sensor?

Read the light

The image sensor has replaced the 35mm film as the receptor of light. This gives many advantages, for example that you don’t have to change film every 24 or 36 images, that you can preview the result immediately and don’t have to wait for the lab to deliver results. Further, you can carry a very large number of pictures on a small memory card and it is easy to transfer the files to a PC for post processing. Most shoot with digital cameras these days, but – just like the revival of the vinyl records – there as some that mix film shooting into their work simply because they like the expression you get this way.

The 35mm film has been replaced by a sensor that is able to read the light it is exposed to.

The image sensor is the unit that has replaced where the film used to be – and this is very literally. The sensor sits in the same position as the film used to do and the size is – provided you shoot full frame – also the same (35 mm).

The camera image sensor, here from the Nikon Z50. In a mirrorless camera the sensor is completely exposed when the lens is removed; on a DSLR the sensor is hidden behind a diagonal positioned glass.

With the introduction of mirrorless cameras you can now actually see the sensor when the glass is removed from the camera body. This also makes the sensor vulnerable to dust and dirt if you change lenses in the field. With a DSLR, the sensor is to some extend protected behind the mirror.

The sensor is not exposed entirely, as there is a thin layer of glass in front of the sensor; otherwise the sensor would be too vulnerable. You can buy sets to clean the sensor and to blow air onto the sensor in order to remove dust and particles. Never remove dust from the sensor using your breath – it contains moist and that is dangerous for your camera in general and the electronics in particular. Always use a (rocket) air blower for such work.

The sensor reads the light just like the film used to do and the values read are then made into an image stored on the memory card in the camera. You cannot change the sensitivity of the sensor, it remains the same as when the sensor left the factory. But you can change the ISO value, which is a factor applied to the light read by the sensor by the cameras image processing software (firmware). Unfortunately, cranking up the ISO means that both signal and noise is amplified, and with a weak signal, it can be difficult for the camera to distinguish between signal and noise. For that reason images taken with high ISO values are grainy and have washed out colors.

Related reading

Is mirrorless cameras better than DSLRs?

Should you upgrade from APS-C to full frame?