Really good explanation for people starting out with photography

[Ysarex83 77]

Awww, it's gone already -- I missed it.

Joe

 

[junni]

linking to articles off site are against the rules.
if you wish people to read the article, post it here instead of as a link to a website.

I could do that! but then the information will be dead, and future corrections and additions will not be there. But maybe i will do that when it's more mature.

I now upload the article here so anyone can comment about things that may be wrong. I tried to give a red line from something most people already is familar with (the maginifying glass) and then take that step by step to the knowledge i have now.

The site contains at this point the following tutorial:

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I'm a simple man and want to see things simply. According to me the simplest way to understand things is the physical point of view. Therefore these explanations will proceed from there. I will not go into vendor specific fancy features of modern cameras, but it will be about the most central things one need to know when doing manual and semi-automatic photographing. These things has newer changed and will be relevant for photographers a long, long time from now


The basic camera explained
Light
Everything in photography can be described as capturing light on a surface. Light from the sun and our artificial lights is illuminating our world, surfaces of objects reflect the light. The reflected (and sometimes direct) light travels to the camera where it passes the lens and hits the sensitive surface on the back of the camera.

Exposure
Exposure is about how bright the photo will be. The sensitive surface, the image sensor in the back of the camera may be a plate covered with light sensitive film, a plastic film with light sensitive crystals or a digital image sensor like in digicameras. When the light hits the sensitive surface, its exposure will increase on the spot where it hit. The longer the light hits the spot and the brighter it is, the more will the spot be exposed.

Color
The light hitting a spot on the image sensor consists of a set of different pure colors. If the image sensor is a color sensor, it usually contains three differently filtered receptors. This make the receptors react to different colors. Usually these colors are red, green and blue. The ligt spot will expose these differently depending on the colors in the color set. It's this this gives us the colors on a picture.

Angle of view
The angle of the picture is simply the maximum and minimum angle of the light that will pass thru the lens and still hits the sensor.

The lens
A camera doesn't need to have a lens, the first cameras didn't have one. In the first cameras the light was simply traveling through a small hole, and then directly hitting the plate at the back of the camera. You may have noticed this effect yourself if you have been in a dark room, and there have been a tiny hole in the wall letting outside light in, since this causes an upside down picture of the landscape outside on the wall opposite to the hole. If you haven't, try it by going into a room with one small window, cover the window with a cardboard with a small hole, so that all light coming into the room comes through the hole. The effect is more noticeable if you put a white paper near the hole because usually the wall is quite far from the hole which will dilute the light.

Why do we have the lens then? This is because with the hole, the image is sharp only if the hole is small. The larger the hole is, the blurrier the image will be and the smaller the hole is, the less light will we get in. This problem is solved by replacing the hole with a lens with a correct focal length (the focal length should be the same as the distance from lens to sensor if we want to focus on objects far away). The lens will focus all the light coming from a specific angle into a point on the image sensor regardless of where on the lens the light goes through. You have surely tried this in your youth with your magnifying glass. The sun causes a small bright spot on your mums tablecloth and leaves behind a beautiful smoking black spot. The black spot is actually an exposure of the sun on the cloth, and the reason you don't manage to get the spot smaller than to a certein point is because when the spot is as smallest there is actually a sharp picture of the sun projected on the cloth

Focusing distance and depth of field
Since the introduction of the lens in cameras we got this effect. It does that the image is sharpest on objects at a given distance from the camera called the "focusing distance". The more the distance of an object deviate from the "focusing distance" the blurrer it becomes

I try to explain it.
Let's take the example of the magnifying glass and the sun. The magnifying glass is positioned above the tablecloth so that the sun is maximally focused. This makes a sharp small image of the sun on the tablecloth. The image is sharp because we adjusted the distance of the magnifying glass so that the (almost) parallelly incoming light from the sun is correctly focused on the cloth. If we replace the sun with a flashlight 50 cm above the magnifying glass the image of the flashlight will be blurred. The reason is that the light from the flashlight will hit the edge of the magnifying glass with a different angle than it hits the centre, while the sun hit's both places with the same angle. The light hitting the magnifying glass near the edge will not be reflected to the same point as the light going through the centre, but by moving the magnifying glass further away from the cloth this will be corrected, and the flashlight will be sharp. This is how one can adjust the focusing distance

The depth of field is the distance from the focusing distance point that still is considered acceptably sharp. In a simple camera with only one lens, the depth of this field depends on the size of the lens. With a larger lens the depth of field will be short, and with a tiny, tiny lens objects at any distance will be sharp.


Terms
Focal length
Focal length is the distance from the optical centre in the lens to the image sensor in the camera. It's the focal lens that determines the angle of the picture. With simple lenses consisting of one symmetric glass lens, the optical centre is in the centre of the glass. With more complex lenses (every DSLR camera lens) that actually are assemblies of a many simple lenses, the optical centre is more complex to determine and depends on the type of the lens (luckily it's written on all lenses). With zoom lenses the optical centre moves when the lens is zoomed, its this movement that causes the zoom effect

Aperture
This is an iris diaphragm / adjustable hole that covers the lens and gives you the ability to control how much light you will get into your camera, this is one way of controlling the exposure. Another very important effect from this is that it affects the "depth of field" since a smaller aperture hides part
of the lens mechanism making the lens act smaller, and as explained that will give a deeper depth of field.

Shutter speed
Since the exposure depends on both light intencity and the exposure time it's nice to be able to control it. Except of controlling shutter speed for adjusting exposure, it can be used in combination with aperture for artistic things like photographing running water on long exposure time, or photographing star rings caused by rotation of the earth

ISO
Faking additional exposure by amplifying the signal from the image sensor before it's digitalized. By raising this value you will add noise to the pictures, but it's necessary when photographing in poor light conditions where the exposure time otherwise would become too long and the pictures would get motion blur. According to me a noisy picture is better than one with a lot of motion blur, and by using it moderately with a good camera it doesn't cause so much noise. This is a similar but better way of doing something like taking a underexposed (too dark) picture and then raising the light levels with a photo editing program

 

[astroNikon]

Awww, it's gone already -- I missed it.

Joe

It was fairly short broken down into segments which were redundant later on, with a menu on the left that jumped to that segment. OP must be from England too as the work Colour was used.

edit: Hey, look ... ^^^ there it is above.

 

[goooner]

It was fairly short broken down into segments which were redundant later on, with a menu on the left that jumped to that segment. OP must be from England too as the work Colour was used.

edit: Hey, look ... ^^^ there it is above.

Or not from the states or Canada

 

[junni]

It was fairly short broken down into segments which were redundant later on, with a menu on the left that jumped to that segment. OP must be from England too as the work Colour was used.

edit: Hey, look ... ^^^ there it is above.

Or not from the states or Canada

I'm actually from Finland, and my english is not the best which you may notice

 

[Ysarex83 77]

The site contains at this point the following tutorial:

You're on the right track with a few things here, but you've also got a lot of errors and confusion going on here. I'll make a few notes to help.

Colour

The light hitting a spot on the image sensor will have a specific colour temperature if it's a clear colour.

"clear" colour is not appropriate terminology -- we don't use the term "clear" colour and it has no meaning.

If it's a greyish color it is a mix of many colour temperatures. If the image sensor is a colour sensor, it usually contains three different types of receptors that react to different colour temperatures. Usually these colour temperatures are the temperatures of red, green and blue. This gives us the colours on a picture.

You seem to be confusing light wavelengths with color temperature. For example white light is made up of the full spectrum of visible wavelengths but nonetheless will have a measurable (single) color temperature.

Focusing distance and depth of field

Since the introduction of the lens in cameras we got this effect. It does that the image is sharpest on objects at a given distance from the camera called the "focusing distance". The more the distance of an object deviate from the "focusing distance" the blurrer it becomes.

I try to explain it.
Let's take the example of the magnifying glass and the sun. The magnifying glass is positioned above the tablecloth so that the sun is maximally focused. This makes a sharp small image of the sun on the tablecloth. The image is sharp because we adjusted the distance of the magnifying glass so that the (almost) parallelly coming light from the sun is correctly focused on the cloth. If we replace the sun with a flashlight 50 cm above the magnifying glass the image of the flashlight will be blurred. The reason is that the light from the flashlight will hit the edge of the magnifying glass with a different angle than it hits the centre, while the sun hit's both places with the same angle. The light hitting the magnifying glass near the edge will not be reflected to the same point as the light going through the centre, but by moving the magnifying glass further away from the cloth this will be corrected, and the flashlight will be sharp. This is how one can adjust the focusing distance

DOF isn't focusing distance. That whole sun, flashlight magnifying glass bit needs to go -- it's a convoluted mess.

The depth of field is the distance from the focusing distance that still is considered acceptably sharp, this point depends on the size of the lens. With a large lens the depth of field will be short, and with a tiny, tiny lens objects at any distance will be sharp

DOF does involve a range of acceptable sharpness. It does not depend on the size of the lens. Lens focal length is one of many factors involved in determining DOF.

Another very important effect from this is that it affects the "depth of field" since a smaller aperture hides parts of the lens making the lens act smaller, and as explained that will give a longer "depth of field".

Making the lens act smaller is not a correct explanation of how the aperture alters DOF.

ISO

Controlling the exposure by amplifying the exposed picture electrically.

ISO is commonly talked about using the "amplification" analogy but that's got a lot of problems. ISO does not control exposure and amplification in the sense of increasing something as the term implies is incorrect.

Back to work.

Joe

 

[table1349]

I'm sure the

I think this does a far better job. Digital Photography Tutorials
Plus it's not spam.

I'm sure you are right in that, but that site is quite heavy. I have collected the most central aspects shortly, and your referenced site may not be the best one to throw at someone that just has started. What i have tried to collect is the things i wish someone would have told me when i started. It may not fit all, but if someone sees it as useful i'm happy. I would also be greatful for replies of faults in the information

Throwing correct concise information is exactly what newbies need. Photography is not some simple little process we can throw a few simple analogies at and have it mean anything. If it was, anybody and everybody would master the craft in a day or two. The art of photography is a complex process based on physics that needs to be understood correctly from the very beginning. Doing so eliminates many beginner issues.

Several misleading errors have already been pointed out in the article so I will not address them. My analogy is simple.....There is no reason to reinvent the wheel, it's already been done and works just fine.

 

[Designer]

Maybe I'll write one someday. Too busy right now.

 

[junni]

The site contains at this point the following tutorial:

You're on the right track with a few things here, but you've also got a lot of errors and confusion going on here. I'll make a few notes to help.

Colour

The light hitting a spot on the image sensor will have a specific colour temperature if it's a clear colour.

"clear" colour is not appropriate terminology -- we don't use the term "clear" colour and it has no meaning.

If it's a greyish color it is a mix of many colour temperatures. If the image sensor is a colour sensor, it usually contains three different types of receptors that react to different colour temperatures. Usually these colour temperatures are the temperatures of red, green and blue. This gives us the colours on a picture.

You seem to be confusing light wavelengths with color temperature. For example white light is made up of the full spectrum of visible wavelengths but nonetheless will have a measurable (single) color temperature.

Focusing distance and depth of field

Since the introduction of the lens in cameras we got this effect. It does that the image is sharpest on objects at a given distance from the camera called the "focusing distance". The more the distance of an object deviate from the "focusing distance" the blurrer it becomes.

I try to explain it.
Let's take the example of the magnifying glass and the sun. The magnifying glass is positioned above the tablecloth so that the sun is maximally focused. This makes a sharp small image of the sun on the tablecloth. The image is sharp because we adjusted the distance of the magnifying glass so that the (almost) parallelly coming light from the sun is correctly focused on the cloth. If we replace the sun with a flashlight 50 cm above the magnifying glass the image of the flashlight will be blurred. The reason is that the light from the flashlight will hit the edge of the magnifying glass with a different angle than it hits the centre, while the sun hit's both places with the same angle. The light hitting the magnifying glass near the edge will not be reflected to the same point as the light going through the centre, but by moving the magnifying glass further away from the cloth this will be corrected, and the flashlight will be sharp. This is how one can adjust the focusing distance

DOF isn't focusing distance. That whole sun, flashlight magnifying glass bit needs to go -- it's a convoluted mess.

The depth of field is the distance from the focusing distance that still is considered acceptably sharp, this point depends on the size of the lens. With a large lens the depth of field will be short, and with a tiny, tiny lens objects at any distance will be sharp

DOF does involve a range of acceptable sharpness. It does not depend on the size of the lens. Lens focal length is one of many factors involved in determining DOF.

Another very important effect from this is that it affects the "depth of field" since a smaller aperture hides parts of the lens making the lens act smaller, and as explained that will give a longer "depth of field".

Making the lens act smaller is not a correct explanation of how the aperture alters DOF.

ISO

Controlling the exposure by amplifying the exposed picture electrically.

ISO is commonly talked about using the "amplification" analogy but that's got a lot of problems. ISO does not control exposure and amplification in the sense of increasing something as the term implies is incorrect.

Back to work.

Joe

Thanks for your reply, Joe. I will study your notes, and many of them are surely correct, and will help me correcting my text. But there may have been som misconceptions. For instance, I never meant that DOF is the same as focusing distance, the way i named my sections may look like that but i will correct it. I agree on your explanations about DOF, and i'm quite sure i understand it correctly. I may need to clarify my examples better, and learn the terminology so that readers get me.

The intension is to make a short intensive tutorial that explains these things by studying something we all are familiar with (The magnification glass), so i would like to laborate with that. Mayby finding more intuitive examples, and later some pictures (They don't lie)

 

[Vtec44]

And this is why I stick to taking photos... lots of pretty photos...

 

[junni]

And this is why I stick to taking photos... lots of pretty photos...

That's the most important thing, isn't it. The mastering of the technology is not enough. Without artistic skills you will not succeed in photography

With only artistic skills one can take excellent pictures using auto.

I'm myself mostly interested about the technical bit which doesn't make me a very good photographer. But it's too interesting to give it up

 

[KmH]

Did you know:
1. The image sensor pixels in a digital camera are not digital. They are analog light sensors that store a small electrical voltage proportional to how much light falls on them during an exposure.

2. The analog light sensors (pixels) cannot 'see' nor record light color temperature. They can only 'see' and record luminosity. In other words they can only 'see' and record shades of gray from white to black.

 

[junni]

Did you know:
1. The image sensor pixels in a digital camera are not digital. They are analog light sensors that store a small electrical voltage proportional to how much light falls on them during an exposure.

I'm aware ofthis, but in the heat of writing, the terminology easilly becomes inexact. Especially when i try to write in a language understood without any photographic background. Still it's good to not have false information, so i will correct this. Thanks for this note

Did you know:
2. The analog light sensors (pixels) cannot 'see' nor record light color temperature. They can only 'see' and record luminosity. In other words they can only 'see' and record shades of gray from white to black.

The sensor sees only the amount of collected photons, yes. But there are grids of color filters that makes a part of the sensor only be hit by photons from the red spectra, another part by the blue spectra and the rest by the green spectra. When i try to explain this simply i say that some pixels see red, some blue and some green.

 

[Vtec44]

To be honest if I was starting out, this article would confuse the crap out of me. LOL

 

[junni]

To be honest if I was starting out, this article would confuse the crap out of me. LOL

I need to rewrite the confusing parts, correct the terminology, and add explaining pictures. The initial parts isn't so confusing, or are they?
This way of learning may not be for everyone. It's for people that has the tendency to stieve after seeing the big abstract picture first, and then learning the details afterwards.

I'm very confident that the model that i'm trying to explain in it self is correct and when i have managed to get it out with good language and correct terminology, it will be simple and fast to learn.

This will not make you good at using your camera since i'm not going into details about camera settings, but it will help you know how it all hangs together