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Photography Through a Hole in a Chocolate Box,or Photo Clinic - Model Railway Photography. - Other Areas. - Your Model Railway Club
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 Posted: Wed Oct 15th, 2008 07:50 pm
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Alan
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Photography For all




This is a thread that has been asked for by the members of this forum, it was going to start out as just a little help in taking better photographs of our layouts, but after all the questions that I have been asked, we thought it might be better to include everything about photography, so bear with me for the first couple of post, as I am going to find information, that I hope will help you all, whether you are a beginner or someone that has years of experience behind a camera, we can all learn something every day.

Ok lets start at the beginning, below is a page which explains all the basics about photography.


Shutter Speeds

Shutter speed is a measure of how long the shutter remains open when the picture is taken. On manual cameras, it is usually set by means of a dial on the top of the camera or, less commonly, a ring around the base of the lens. Automatic cameras usually denote shutter priority mode with the symbol Tv which simply means "Time value". Typical shutter speeds are 1/1000s, 1/250s, 1/60,1/15s and 1s. Note that shutter speeds are calibrated to be approximately twice as fast as the previous setting and twice as slow as the next setting. For example, 1/250s is twice as fast as the previous setting 1/125s but is twice as slow as the next setting 1/500s. 





There is often an extra shutter speed for bulb exposures in which the shutter remains open for as long as the shutter release button is held down. This is handy for exposures of several minutes, such as this night-time shot on the left.
Most modern SLR cameras have shutters known as focal-plane shutters. Associated with this type of shutter is a flash-sync speed which is the fastest permitted shutter speed when using flash.
Shutter speed plays an important role in avoiding camera shake which happens when the camera moves relative to the subject whilst the shutter is open, causing an overall blur. To avoid this, a good rule of thumb is select a shutter speed which is near to, or faster than, one divided by the focal lenth of the lens. For example, with a 50mm lens the slowest hand-held shutter speed would be 1/60s and with a 300mm lens it would be 1/500s. 
 


Aperture



The technical definition of aperture vaule, or f-stop as it is often known, is the ratio of the focal lenth of the lens to the diameter of the lens opening. In other words, it is the number of times the diameter of the hole through which the light has to pass will fit into the focal length of the lens. The size of this hole, known as the aperture, may be controlled by turning a collar usually located at the base of the lens. On automatic cameras, aperture priority mode is often denoted by Av which means "Aperture value". Typical values may be f2, f2.8, f5.6 and f16 where the "f" denotes the f-stop, often referred to as f-numbers.
Fortunately, for most of the time we don't have to think of the aperture value in terms of its technical definition or precise meaning! All we need to know is that smaller f-numbers (f2, f2.8 etc.) represent wider apertures (i.e. more light can pass through the lens in a given time) and higher f-numbers (f11, f16, f22 etc.) give narrower apertures (meaning that less light passes through in a given time). The clever bit about this confusing arrangement is that the f-stops are calibrated to allow exactly half as much light through as the previous setting and twice as much light through as the next setting (in a given time of course). For example, a lens set at f8 will allow twice as much light through as one set at f11 but only half as much as one set as f5.6. It's no coincidence that shutter speeds are also calibrated to be twice as fast or slow as the next or previous setting which allows us to see how changing the aperture affects the shutter speed required and vice versa.





Depth Of Field







Depth of field can be thought of as the amount of the image which has acceptable sharpness. This means that either side of the selected point of focus, there is a region in which the image remains in focus. Moving outside of this band of focus (towards or away from the lens), the image becomes progressively more unsharp and out of focus.
The amount of depth of field is controlled solely by magnification and aperture. Since the magnification is normally fixed for a given suject, the depth of field is usually controlled by aperture alone. Wide apertures (such as f2, f2.8) give less depth of field whilst narrow apertures (such as f16, f22) give much more depth of field.
This control is very important when deciding how to isolate a subject or where to direct the viewer's attention. Look at the picture top right which is a townscape view  with a garden rockery in the foreground. The foreground was only a few feet from the camera and the background view stretches to infinity (virtually!). To maintain such a great depth of field on the 50mm lens used, it was necessary to select the narrowest available aperture of f22. Careful focussing using the depth of field scale, which is usually marked on the focussing scale of the lens, showed that sufficient depth of field was available at the minimum aperture. 







The picture  uses shallow depth of field to direct the viewer's attention to the subject (this is not as easy to see on the small picture, click inside the frame to receive a larger version). Notice how the immediate foreground and the background are out of focus, but there is a band of focus (look on the path) in which the subject sits.
This technique of isolating the subject using depth of field is very effective, particularly for portraits , in which the viewer's attention should be directed to the subject and the background left out of focus to avoid clutter. Note how the background can still be important, although out of focus, to indicate location or the mood of the shot. 




Focal Length





 
One of the most significant properties of a lens is its focal length. Loosely speaking, the focal length of a lens is the distance that it should be held from a screen in order to project a focussed image on that screen. This is not exactly true for camera lenses which are actually made from complex combinations of single lenses. Fortunately a 500mm lens does not necessarily have to be 500mm long! The importance of focal length is the angle of view obtained. The longer the focal length, the narrower the angle of view and the more magnified the image is (at a fixed distance). Short focal length lenses are known as wide-angle with typical focal lengths of 20mm, 24mm and 35mm. Standard focal length lenses are around the 50mm mark and the range 80mm-300mm are considered telephoto lenses. Anything above 300mm is regarded as super-telephoto.
To illustrate this, look at the pictures of the telephone boxes (top left and below right). The picture on the left was taken with a wide-angle 24mm lens and the one on the right with a telephoto 300mm lens. Notice how, in both cases, the telephone boxes fill the frame, but the perspective in each shot is very different. Telephoto lenses tend to compress perspective making objects look closer together, whilst wide-angle lenses distort and can make fairly close objects (such as the furthest telephone box) seem very distant.
Contrary to popular belief, depth of field does not depend on the focal length of the lens. Depth of field is determined only by the magnification of the image, and although telephoto lenses magnify more than wide-angles (at the same distance), the depth of field in a picture taken by a 24mm lens will be the same as that in one taken by a 300mm lens if the subject is the same size in each. Therefore, the depth of field in the two pictures of the telephone boxes is the same!
This picture on the left was taken with a wide-angle lens, and shows the distorting effect they can have on ordinary subjects.







Flash




Many people are reluctant to use flash with an SLR camera, either because they think it's too difficult or because they've tried it before but with poor results. Other people think that flash is only useful indoors when there is not enough light. None of this need be the case - using flash can be very easy and also very creative! This picture on the left was produced using multiple flash exposures, moving the subject between each one. Many other creative examples are easily achieved with even the most basic of flashguns.
However, first it is necessary to understand the following simple technical details about flash:


  • Flash-Sync Speed: We have already seen, in the section on shutter speeds, that most SLR cameras have a maximum shutter speed for use with flash called the flash-sync speed. Commonly this will be about 1/125s and is often marked with an "X" or a flash icon on the shutter speed dial. You must select a shutter speed at or below this setting, eg. 1/60s.



  • Exposure Control: The amount of light reaching the film from the flashgun is controlled purely by fill flash). With a manual flashgun you will need to calculate the aperture from the guide number (see next item). Automatic flashguns have a sensor on the flash which measures how much light is reflected from the subject and tells the flash when to cut off. film speed of ISO 100 and allowance must be made for faster or slower films by adjusting the aperture accordingly.
Most important of all, you should get to know your flashgun intimately. If it has different settings or a distance calculation scale, play with them - don't be afraid to experiment; waste some film if necessary! Some flashguns even have a separate manual - read it! Together with the basic details above, at the very least you will have fun and you might end up with some great pictures!

 



Other Uses for Flash



The light output from a typical flashgun lasts between 1/1000s and 1/10,000s (depending on power) which is enough to freeze most subjects, moving or not! Unfortunately, most fast moving subjects will be out of range of a flash exposure, but when it is possible to get close enough a good technique is slow-sync flash. The idea is to select a slow shutter speed (metered for the ambient light) and at the same time "freeze" the subject with the correct flash exposure. Results can be unpredicatable, but depending on shutter speed, you will see the moving subject frozen in time with a streaky "ghost" image in front or behind. This is a very good technique to indicate movement in sports such as cycling or rallying. If you try this then find out about rear-curtain sync (if your flashgun/camera has it).
Slow-sync flash can also be useful during long exposures (such as an floodlit building at night) to provide illumination to the foreground.
Flash is particularly useful in close-up and macro photography where small apertures would normally require long shutter speeds leading to problems with camera shake. The very short distances involved (< 1m) mean that even the most pathetic flashes (GN around 10) can be used with small apertures. Specially for close-up work, a ring-flash, which is a flash with a tube shaped like a doughnut, is designed to fit around the front of the lens and provide shadowless lighting.




Close-up and Macro Photography 





 







Close-ups and macro photography are particular favourites of mine, and that's why there are so many pictures in this section!! There are four major categories of this type of photography:


  • Close-up - magnifications between 1:10 and 1:2;
  • Extreme close-up - magnifications between 1:2 and 1:1;
  • Macro - the true macro range, 1:1 and above;
  • High magnification - microphotography, 10:1 and beyond.
The magnifications refer to the size of the image on the film compared to its size in reality. Thus 1:1 is life size, 1:2 half life size etc. Most lenses have a "macro" setting marked on the focusing scale, but this is not true macro, just extreme close-up. There are several ways to obtain good close-up pictures. A close-up dioptre lens, which screws on to the front of the camera lens, is perhaps the cheapest way of making your standard lens focus closer. Several of these lenses may be used together to acheive magnifications up to about life-size. Unfortunately, quality begins to suffer, particularly around the edges of the image, as magnification increases. Extension tubes fitted between the camera and the lens will also decrease the minimum focussing distance. Metering may become a problem since quite a lot of light is lost due to the extension, and exposure times of several seconds may be required. 




Both of the above methods require a standard lens to do something which it is not really designed for; that is focus very close to the subject. Lenses which are specifically designed to focus at close distances are called macro lenses (even though they may not always cover the true macro range) and should give high quality results if used properly. All of the images in this section were taken with a 50mm macro lens. The flower arrangement (top left) could be described as being in the close-up range. Moving in closer, the flower picture on the right is an extreme close-up of magnification about 1:2. 




The subject magnification increases, the depth of field decreases drastically! At life-size magnification the depth of field at f2 is 0.24mm, at f4 it is 0.48mm increasing to just 3.8mm at the maximum f-stop (for my lens) of f32. Such narrow apertures can require very long shutter speeds which means that steady support is needed to avoid camera shake. A sturdy tripod is essential although problems with even the smallest vibrations (such as the reflex mirror flipping up) may be encountered at such high magnifications.


Possibly the best solution to this problem of camera shake is to use flash. If the flashgun is mounted on the camera in the usual way, the lens may cast a shadow over the subject due to how close the lens is focussing. To overcome this, the flash may be connected to the camera with a flash-sync lead, which is basically a length of wire but will still cost you 30 quid for a TTL version! This picture on the right was taken at life-size, with an aperture of f32, using a flashgun and off-camera flash sync-lead. The flash has provided a nice catchlight in the eye and good depth of field has been maintained.





Could members please post their comments on this topic in the thread I have opened called "Comments On Alan's Photography Tutorial". Thank you.

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 Posted: Thu Oct 16th, 2008 08:30 am
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Alan
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To Flash or Not





Below I show three different images




First photo



Built in flash on camera on



ISO 160    f5     Shutter Speed 1/60









Second Photo


Flash Turned off

ISO 250      f5     shutter Speed 1/6









Third Photo


Flash Turned off


ISO 250     f11     Shutter Speed 1 second






With the last image showing how I set the camera up, you do not need fancy tripods, the big must is that the camera is still, use your delayed action/ self timer, which will stop any movement at the time that the shutter opens.





Hopefully you can see the difference in all the photos, but by using available light,  the photo has a more natural look to it, and it will always be sharper, if you use your aperture correctly, if you have a camera that does not allow you to alter the aperture, then look in the menu, and see if you can alter the ISO, from 100 to maybe 400 or even higher, this will in effect alter the aperture for you, but take acouple of photos, using both and see for yourself. if the lighting in your room is not good, then use a desk light which can be used as a overhead light, This can be a very handy tool, which we can talk about at a later date.













 








Could members please post their comments on this topic in the thread I have opened called "Comments On Alan's Photography Tutorial". Thank you.













 

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 Posted: Fri Oct 24th, 2008 01:43 pm
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Alan
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Depth of Field/Focus





Below I hope to help with the depth of field/focus question. I have taken four photos all from the same place, and the only thing that I have changed is the aperture, the camera is very close, Wide angle macro, which helps to show the shallow depth of focus on the first image. By upping the aperture ( allowing less light onto the subject, which means a longer shutter speed) the depth of focus grows, so at an aperture of f5.6 only the front of the loco is Sharpe, but as you go up to f16, more of the loco and surrounding area's become Sharpe.





First Image





ISO 160





F5.6









Second Image





F8









Third Image





F11









Fourth Image





F16





 









Hope that this has explained a little more regarding DEPTH OF FOCUS, the same applies when a photograph is taken from further away from the subject, but the difference is a little harder to notice.





 

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 Posted: Mon Dec 15th, 2008 04:37 pm
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Alan
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Quick Mini Studio


at Home

This is going to be a two part tutorial with a quick set-up studio for the first one ( this one ) and a more professional studio set-up in the second one.




For this studio, all I have used is a piece of off-white backing card and a normal desk light, the first photo's show a wagon photographed on a normal workbench ! and the second shows the set-up.



both the photo's below are taken just using the sunlight coming in for a window behind 








This first photo is also taken just using the sunlight, exposure = 100iso f16 at 30th



the next image has be taken by using the desk lamp ( this has a standard 60w bulb in it ) and placing the light to the right of the camera about level with the front of the camera, this has given us a flat light, with a shadow to the left.



This next image is the same as above except that the light has been moved to the left of the camera, giving again a very flat light, with shadow to the right of the wagon



The last image shows a close-up using the above lighting, which is better than a complete full wagon, as you are seeing a better lit area.



All the above images have been taken using the following exposure

100 iso f16 at 30th

None of the images have been taken with flash, which is why they have a very warm feel to them, using flash in a studio setup will be covered in the next tutorial. This is not the best type of mini studio, but you can see that it does work, it would be better if you used plain white paper, as that would reflect a little light up onto the subject, and also only using one light ( that has a normal 60w bulb ) gives a very flat lit subject, that does not really give any punch to the photograph, but I am going to show the difference in the next tutorial, along with using more than one light.

Hope that this has helped some of you, and I hope that I can upload the second tutorial very soon

 

 



Could members please post their comments on this topic in the thread I have opened called "Comments On Alan's Photography Tutorial". Thank you.




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