The Basics of How a Camera Lens Works

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Lenses and Focusing

This is what lesson 2 of the Photography 101 course that I am following has been looking at. I have found it really interesting because knowing how a lens works and focuses in on a subject, helps me to understand more when things go wrong or wont work how I want them to!

It looks at how light bends or refracts and how it then reacts when traveling through or onto a surface or object. For example if light hits the surface of water at an angle then because one edge of the ray of light has hit the water first it will bend. How much it bends depends on the angle it hit the water in the first place.

Lenses

And that’s how lenses work, by bending the light coming through the lens we can get the light to focus on one point. Depending on how much the lens is able to bend or refract the light, and what angle the light hits the lens.

Focusing

And that’s where focusing comes in. If parallel light hits a lens it will pass through and converge at the same point. But if the light hits the lens at an angle then the lens bends the light to focus on one point. The point at which the light then meets again on the other side of the lens is called the focal point, and that changes depending on how much the light has been bent. The distance from the lens to the focal point is measured in mm which you will recognize from the way different lenses are described.

Now we get to the homework

Every week there is a list of homework choices that you can have a go at, which is great because it helps me to cement in my mind what has been taught in the lesson. So this week I chose to demonstrate the refraction of light by doing the old pencil in a bowl of water experiment.

As you can see in the photos it shows exactly what I have been trying to explain! I always like to see a visual explanation, it’s just easier to understand.

I also noticed that the rim of the bowl that is thicker than the rest of the bowl, refracts the light as well. Which reminds me even more of a lens.

I’m enjoying posting about the course in this way, although it’s not a detailed review of the lesson’s it’s my way of confirming what I have learned. To post and talk about the new knowledge I now have helps me remember it, and using it increases my understanding of it. I hope it helps you too by giving a very simplified view of the excellent lessons in the Photography 101 course.
Mandy

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Photography 101 - 2nd Lesson

This week the second lesson of the Photography 101 course that I’m following is looking at lenses and focus.

Looking at the theoretical side to bending light, lenses and focusing. Some people haven’t liked the fact that the two lessons have been based around theory, and want to get down to the nitty gritty of taking photos. But I can see where Neil Creek who is writing the course is coming from.

It’s a long time since I was in a physics lesson, which I did used to enjoy. But at the time I didn’t see the relevance for physics in everyday life outside of a lab, yes I liked the cool experiments that we did, but I was only young and more interested in the latest rock and pop bands of the day!

But now I can see how physics is a fundamental and very important part of photography and me being able to do it better. If I can understand the basics of how light behaves and how my equipment deals with that, then I am in a better position for making the right choices in settings and lenses when taking photographs. I always find I am better at understanding something if I know how it works rather than just being told it works.

I’ve found these lessons really interesting and I’m learning a lot, or should I say remembering a lot (of physics anyway)!
Looking forward to lesson 3…

Mandy

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How to Make a Camera Obscura

Making a Camera Obscura is one of the homework choices for lesson 1 of the Photography 101 course on the Digital Photography School Blog.

What is a Camera Obscura?

Camera Obscura or ‘dark chamber’ is one of the earliest ways of producing an image, the idea is very old and first documented a 1,000 years ago.

Basically it is a lightproof box or room with a small hole in one end, light travels through the hole and forms an image on the opposite side or wall to the hole. Because of the way that light travels and behaves the image that is produced is up side down.

Due to the small hole only letting a bit of light through the image is faint but has very good perspective and detail. If you made a larger hole the image would be stronger, but the more rays of light that pass through the hole the more they overlap, and consequently the image is not as sharp. The small hole directs the light better.

This gives us a basic understanding of how the aperture works on a camera, and how the size of the aperture and the amount of light that passes through it affects the image that is created.

So what did I do?

I decided to use my spare room to make my camera obscura, it only has one window and is very handily box shaped. I completely covered the window in a combination of foil and masking tape, making sure there was no light getting through, or as much as I could anyway. Then I made a small hole in the middle of the foil. I also made a screen for the image and propped it up in front of the window. My wallpaper is textured and I didn’t want to be too optimistic about how well the image would make it to the wall!

It didn’t work the first time…

These things never do. It worked in the fact that there was an image on the screen, but it was a reflection of the foil on my window. It was a very sunny day so the foil image was quite strong, because the foil was doing what it does best and reflecting that well (and getting quite hot) I think it was starting to cook the window.

So I had to redesign slightly and cover the back of the foil with paper to stop it reflecting. That did the trick though and sure enough an image of the houses across the road appeared on the screen, but up side down. And not as strong as the foil image, but I could see the detail of the clouds and the chimneys of the houses.

Was it worth it?

Oh yes, it was absolutely great when the image appeared on the screen. I really felt like I had achieved something, and I could say I had 100% created that image from basically foil, paper and masking tape. I was made up with it, and it was a lot of fun.

Unfortunately as much as I tried to take a photo of what I had done, my camera (a point and shoot) was not up to the job of shooting in such low light. So I haven’t got any photos of it, but I have shared some pictures of what the camera obscura looked like so you can get a feel for how it worked.

Mandy

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What is a pinhole camera?

Until this week I didn’t really know much about pinhole camera’s, ok I knew they were one of the first types of camera’s and very basic using a hole instead of a lens. But I had no idea what the photographs looked like or how you made and used one.

What is a pinhole camera?

It is the simplest of image making devices, it’s basically a light tight box with a small hole in one end, on the opposite side of the box is photographic film or paper which records the image (or light) that passes through the hole. Due to the way in which light behaves the image appears up side down on the back side of the box. I heard about them from the Photography 101 course I am following on the Digital Photography School blog which I talked about in my last post.

So how do you make one?

I had an image in my head of a pinhole camera being very old and made out of polished wood! I was amazed when I found out they are used widely today and can be made out of just about any kind of box or can. So much for what I know! There are loads of great pinhole images on flickr if you want to see what they look like.

You can buy kits that you can build yourself which sounds kind of cool, I like the idea of making a camera from scratch and then taking photos with it. And there are loads of different kits around to choose from. Take a look at these examples, pinhole camera kits.

Or you can make one from scratch out of household things, people have made pinhole cameras out of coffee tins, cereal boxs, cookie tins by the sound of it pretty much anything. Take a look:

Oatmeal box pinhole camera
Pinhole polaroid camera
Pringles pinhole camera

This is definitely the hands on technique, but I’m not sure about working out (and getting it right) the exposure time by measuring the size of the hole against the distance from the hole to the film. It sounds like a little bit of trial and error, but that’s what this type of photography is all about doing it completely from scratch, and knowing you really did create the image!

I never considered using a pinhole camera before, but I’m really interested to have a go now!

Mandy

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Photography 101 - First Lesson?

Did anyone else go over to the Digital Photography School blog on Monday and read Neil Creek’s first lesson of the Photography 101 course, Light and the Pinhole camera?

I did and I found it really interesting. He is starting with the basics of how photography works which I like, because the better the foundation and knowledge of how photography works the better understanding I will have to take photographs.

Light

He starts off with a basic introduction to light and how it behaves, which takes me back to my physics lessons in school. Seeing as you capture differing levels of light to make an image it’s good to understand a little about light.

Pinhole Camera

Next he looks at how you can capture that light, by explaining about Camera Obscura’s which have been used for 1,000’s of years and are the forerunners to the modern camera. The idea is you have a box (which can be room sized) with a pinhole in one end, the light will then travel through the hole and hit the opposite side or wall to form an image (upside down). Obviously the box has to be light proof except for the hole. Camera Obscura’s were used by artists who would use paper or canvas on the opposite wall of the camera obscura to trace the image produced by the hole.

Pinhole camera’s work the same as camera obscura’s and are usually made out of some sort of box with photographic film or paper attached to the back side to capture the image. You can see how camera’s developed from this, the hole being the aperture of the camera.

Homework assignments

At the end of each lesson there are a list of homework assignments that you can do if you would like, this week I have chosen to make my own camera obscura - hopefully!

The idea being that you choose a room with one window and completely cover the window with card or foil blocking out all the light, and then put a pinhole in the covering, you should then see an image appear on the opposite wall (hopefully) of the outside, but upside down. I’ll let you know how it goes!

There are several room size camera obscura’s around that you can go and visit instead of making one, here’s a few:

Royal Observatory Greenwich, London
Dumfries Museum & Camera Obscura
Griffith Observatory, California
Havana, Cuba Camera Obscura
North Carolina Museum of Art

Mandy

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Looking at Size and Quality Settings

Have you ever wondered why every time you transfer a photo to your computer it is so large. And wondered why, I know I have. Is it a camera setting or the photo editing software that you are using?

Size Setting

But then I noticed I have a size setting on my camera, in other words setting the number of pixels that can be used in the image.

My camera’s default setting is 2560 x 1920 pixels which is also the highest setting without interpolation. Once in the photo editing software it is 90 x 67cm with a 28.346 pixels/cm. That’s huge. I also have some other pixel options on the camera and they are:

3072 x 2304 (interpolation)
2048 x 1536
1280 x 960
640 x 480

The more pixels the better and sharper the image will look and thats also why the photos come out so large, the more pixels the bigger the file size.

Quality Setting

Underneath the size setting I noticed a quality setting for images. Which gives me a choice of:

Fine - low compression rate
Normal - Normal
Economy - High compression rate

Conclusion

At the end of the day I want to take photographs that are high in quality and look sharp enhancing the detail in the shot. So the setting I would keep as high as possible and play around with the normal or low compression rate.

I think these settings are geared towards increasing the amount of images that you can take on the camera. And that would only be useful if you have a small memory card. I use a 1gb memory card and that is plenty for me, I can take up to 1,000 photos on my camera using the 2560 x 1920 size setting. Although that may change if I use a low compression rate I can’t see it changing the amount of photos I can take drastically.

Mandy

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My Digital Camera ISO Experiment

Following on from Wednesdays post about digital camera ISO I thought it would be good to stop talking about it and give it a go.

So I did, but seeing as I didn’t have any low light shooting opportunities coming up I decided to use my mouse as a substitute.

The photograph on the top is taken using the 100 ISO setting on my camera and the photograph on the bottom is taken using the 200 ISO setting on my camera. And these are the only two options I have for ISO besides the auto setting where the camera will automatically decide which is the best between the two.

Results…

I took the shots using a mini desktop tripod and no flash. Which really gave the camera a good workout because it was really low light!

There isn’t a huge difference between the two photographs but there is some, and taking into account that I don’t have much ISO range on my camera anyway, I think it is quite a good result. What I wanted to achieve was to see the difference (if any) between the ISO settings on my camera. They show that using a camera’s ISO settings in low light with no flash is a realistic option and one I will experiment with further.

It will be great for when flash photography isn’t allowed, like concert or school performances. And I can see that there will be slightly different effects with each settings depending on what I want to do with the photograph. Looks like fun!

Mandy

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What is Digital Camera ISO?

Back in the old days when I had a film camera, ISO was to do with the film and it’s speed. I generally used ISO 100, 200 and 400, for bright conditions, cloudy conditions and all round conditions respectively.

It’s a little different with digital camera ISO

What is digital camera ISO?

Digital ISO gives an indication of the sensitivity of the camera’s image sensor (what would be a comparison to film).

And can be adjusted depending on how much light is entering the camera. Which sounds a little like EV compensation to me, but it isn’t!

The lower the camera’s ISO the better the image quality of the photographs.

The higher the ISO setting the more chance there is of the image having digital noise (depending on your image sensor).

So what is noise?

Briefly it occurs when the ISO has been set high and therefore the image sensor is very sensitive to the amount of light coming into the camera, but also sensitive to anything else as well. And that results in noise or ‘dots’ appearing in the image.

The size of the image sensor in your camera is directly related to it’s ISO speed range and how large it can be. It can go as low as 50 or up into the 1,000’s, each camera will have it’s own range. Point and shoots only have small sensors so a high ISO will cause noise. Where as DSLR camera’s have large sensors so noise is not so much of a problem and higher ISO’s can be achieved.

Why would I use it?

If you are in a low light situation where you want to take a picture but can’t get the right exposure because you can’t use a flash, then using a higher ISO to get the right exposure for the picture is the best option, and will let you take the picture.

This can increase the risk of noise in the image. But I would take the photograph anyway because you can use post production software to remove most of the noise afterwards.

Digital cameras will have an auto ISO setting as well, and the camera will automatically select a higher ISO when light conditions are low, but you may want to adjust this.

My Camera

My camera has an auto ISO setting and a choice of 100 and 200 ISO settings. So the auto setting will decide between the two in low light if I don’t choose one myself.

Mandy

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Camera Colour Features v’s Photoshop

My camera has an option to change the colour settings of the camera to full colour, black & white or sepia. So I went out to give them a try as I have’nt used them before. These three photographs are the result. It was a dull day and it was raining so I picked a subject that was full of colour to give greater contrast.

I used to sometimes shoot in black and white film on my old camera so it’s nice to be able to just flick between the two (colour and black and white) whenever I feel like it.

Although the detail is good I don’t think I would shoot a lot in sepia unless for a specific need.

But if shooting in black and white or sepia solely and not using colour for that subject then there is no turning back.

Once you get home you can’t add the colour again so it’s something to think about.

But you can always shoot in colour (as well) and then change it later in Photoshop, or is that cheating!

Photoshop

These next three photographs have been produced in Photoshop Elements, the black and white and sepia anyway. So you can compare the two sets of photographs.

The full colour photograph is in RGB colour.

The black and white one has had the colour removed in the colour adjustment palette.

And the sepia one has been created in the colour adjustment palette by adding blue and red.

If you were comparing all six photographs together I don’t think you could guess which was which if you didn’t know beforehand. The first three look a little sharper but that could be the subject, to properly compare I should have used the same photo but I thought that would look a little monotonous.

So I think it’s down to a question of taste - camera or Photoshop (whichever version you prefer). I think I would choose photoshop because it gives a bit more flexibility, but that’s easy to say as I have used it a lot.

But one thing I will say is the Photoshop Elements produced photos uploaded to my blog a lot quicker than the ones that were produced on the camera.

Mandy

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Movie Mode - How Good is it?

A lot of manufactures make digital cameras with a movie mode or video camera capabilities (although limited), but are they any good?

Personally I feel that a camera is best for taking photographs and a video camera is best for shooting movies. Most video cameras have a still frame mode as a digital camera feature as well.

Although both of these types of cameras, digital camera or video camera are supposed to make life easier because they are 2 in 1, having each others features these addon functions to me never seem any good.

Video verses camera resolutions

For instance my camera has a movie mode option and I decided to take a look at the resolutions for both the movie mode and the photography mode.

video mode: 320 x 240 pixels
photography mode: 2560 x 1920 pixels

So from that you can see the difference in the quality of the shots that will be produced by both of these modes, the more pixels the better. The video mode being very poor.

I think at the end of the day it’s best to take both a digital camera and a video camera if you are looking to use both, and then you will get descent images from both. Although when I just want to capture the odd bit of video then I have found just using a digital cameras video mode to be fine.

Mandy

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