Hello, Welcome TX Stock Photos Blog

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Hello, Welcome to TXStockPhotos, here in my blog I will discuss matters of significance in the camera world, and give simple and easy to follow tutorials in Photoshop Elements.

Check out my How to Photograph… page, where you can read tutorials on photographing various subjects

While my main site is still under construction, It will soon be ready, and you will be able to purchase outstanding images, that take photography to a new perspective.

Hope you enjoy my website, and find my tips helpful. Please submit any feedback, anything you liked, anything that could be improved etc.

Highlight of Iceland Gallery

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These pictures are for general viewing only, and cannot be used without my permission. I took these images as documentation on a visit to Iceland in 2012.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

How to shoot Sharp Landscapes Every Time

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It is so disappointing to get home from that iconic location, only to find that on your computer screen, your images are out of focus. This can happen to anyone, even advanced photographers, but there are ways to combat it. In this article I will explain depth of field*, hyperfocal distance and circle of confusion (CoC).

As we have seen in my post on aperture*, it plays a major role in determining how much of the image is in focus. As the post explains, larger f numbers (narrower apertures) have a deeper depth of field, and therefore constitute sharp images. While this does help, it is not the only option available to the more advanced photographer. The easy way out is to use infinity focus, shown on your camera as a sideways 8. This does have it drawbacks though, and another option is to calculate and use the hyperfocal distance.

This is a lot more complex. It involves the circle of confusion, and aperture, and focus distance. You can then calculate the hyperfocal distance, and achieve perfect focus from a few feet away, to infinity.

Circle of confusion is a term that often dampens the listener’s mood. It is a concept that is  hard to explain, and even more so to understand. It is a measurement (a fraction of a millimetre) that is inserted into the equation used to calculate hyperfocal distance.

It works with the following fact. When we capture an image on our small sensors, and magnify them, we also magnify their faults, so say we selected on an object that was 5 m away, but instead we focused for 6 metres. There would be a slight degree of out of focus-ness which would be magnified when we print the image, or view it on a computer. The point where the CoC become visible is the point where the region concerned crosses the boundaries of the ”acceptably sharp” area, or the Depth of Field.

Hyperfocal distance is the distance at which we have to focus to achieve acceptable sharpness from near to infinity. These days technology such as iPhone have DoF calculator apps, but old lenses had a calculator on their barrel. Just set the lens to infinity and the aperture you want and you will be pointed to an appropriate hyperfocal distance. Modern lenses have unfortunately lost this feature, but DoFmaster is available online to calculate. Also, for the more mathematically minded, it is possible to use the formula below.

 

H= Hyperfocal distance

F= focal length

Fn= F number

C=CoC

The resulting number is the Hyperfocal distance, focus at that distance, and acceptable sharpness from near to infinity should be yours.

Do note, that even in the plane of focus, using the cameras smallest aperture causes softening of the image due to a large CoC thanks (or no thanks!!) to a process called diffraction*.

 

*Link will open in new tab.

How To Photograph Moving Subjects While Using Blur Creatively: Successul Panning Photography

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We have all seen those images in a motor magazine – perfectly sharp, crisp cars, and streaked, blurred backgrounds. These photos are usually taken by a pro, or photoshopped, but that doesn’t stop you recreating the effect!! With a few of the tips below you can easily take your own stunning panning image*

*In this tutuorial I will use cars as an example, but this technique can be used with many sports, and can also be recreated in photoshop.

To begin with, you need a subject. Cars are a good starting point because their wheels go round and round, unlike say a horse, where the legs are all over the place!!!

Once you have chosen a subject, find a display, etc that is on soon (if using general cars, just head to the nearest clear road. If you photograph cars without the owners permission, do not use them commercially).

Select a slow-ish shutterspeed of 1/80 or 1/100. You can always use a slower shutterspeed if you want longer streaks of blur, but /100 is a good starting place, because it is easier to get it right. Stand with your legs apart to help you balance, and hold your camera level with where your subject will pass. Concentrate on your subject, and when the moment is right, press the shutter button down, and follow the movement. It really helps if you ground yourself firmly, and move from your hips. This helps keep you steady, and increases your chances of a good shot.

This is all very well, but you can always use a fast shutterspeed (over 1/1000) and add motion blur later in photoshop. The downside of this is that people can tell if you have photoshopped the image by looking at the wheel spokes. If they are sharp, and the background is blurred, a photoshop diva has been at work!!!

 

 

Sensor Size- And how it affects your photography

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Camera sensors have many different sizes. A full frame sensor is 36x24mm in size, and a camera sensor that is maller is regarded with a certain degree of ‘crop factor’.

The degrees currently in general use are shown below.

Another factor must be taken into consideration. If you used a full frame camera to photograph a landscape with a 50mm lens, the scene would appear the same size as it is in reality (50mm is considered 1x zoom). On the other hand, if  you used a 1.5 CF camera, the lenses focal length would be equivalent to 75mm. A 1.6x CF sensor with 50mm lens has the equivalent to 80mm, but be warned, this can be confusing. The focal length is not actually altered, simply the angle of view.

While it seems that discarding information in this way is not only wasteful, but also annoying, it does have its advantages. For example, the image is likely to have more overall sharpness. This is enhanced with low quality lenses, because the edge information is usually the worst quality.

A larger sensor has a shallower depth of field. This means that to achieve the same depth of field, you need a narrower aperture. A shallower aperture is often prefered for portraits and macro..This is why it is easier for DSLRs to produce blurred backgrounds.

Diffraction ”Airy disk” will take over at narrower apertures, when it becomes larger than the circle of confusion and this makes the images softer, but larger sensors can use smaller apertures before this begins to happen. Diffraction limits are adressed here.

Larger sensor generally have larger pixels, and this can create higher  dynamic range, and even improved noise reduction.

As sensor size doubles, so does the price. There are also other considerations, including there are less fast lenses available for cropped sensors. The same applies to wide angle or superzoom one.

Finally, tilt ans shift lenses can alter the actual appearance of depth of field.

 

 

 

 

 

How Digital Camera Sensors Work

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In this article I will give you a brief overview of how a digital camera’s sensor works.

A camera sensor uses millions of tiny pixels (each megapixel has one million pixels!) When the shutter opens, a photosite is uncovered, and a small cavity collects photons (light particles). Photosites gather different amount of photons according to the bit depth (255 are collected for an 8 bit image).

A cavity cannot distinguish how many photon of a particular colour have fallen in, so this would give rise to a grayscale (black and white) image. Therefore, a filter is placed over every cavity, so only a certain colour can pass through.

A bayer array consists of alternating row of red and green and a row of green and blue filters. Having twice as much green helps the human eye perceive the image as less noisey and with finer detail because the eye is more sensitive to green wavelengths.

There is a process known as Bayer demosaicing,which  converts primary colours into the final, full colour image. It does this by treating a 2×2 array as one unit. A 2×2 unit is made up of two green, one red and one blue photosite.

More information can be extracted by overlapping each of the 2×2 arrays, therefore achieving higher resolution.

Other demosaicing algorithms are available, such as X3 technology, where red, green and blue photosites are embedded in silicon.

Some more advanced cameras use cyan, magenta, green and yellow to demosaic, instead of the more common green, red and blue array. Some cameras even go as far as having two sensor, though in general, consumer priced cameras use the Bayer array.

During demosaicing, artifacts can occur. These are unrealistic patterns caused by a faulty reading. One classic example is chromatic abberation, or , more commonly ‘purple fringing’. The most common artifact is a moiré (pronounced moray). This may appear as stumped, or repeating patterns.

The whole sensor is not covered in photosites, and they are generally not arranged perfectly. In fact, space is left on the sensor to accomodate other technology, such as ‘microlenses’ which act as channels, directing the light to the photosites, and enhancing their photon-gathering ability.

You can also view my article on Sensor size- And how it affects your photography

Nikon recalls D7000/D800/V1 EN-EL15 Batteries due to safety issue

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If you own a D800, D800E, D7000, or V1, lookout, because Nikon have discovered a afety issue concerning EN-EL15 rechargable batteries overheating, and deforming and damaging the cameras outer casing*. No consumers have been injured, but this could occur in a more serious case.

Anybody who has one of the conforming Nikon D-camera whose batteryhas a ninth serial digit of ”F” or ”E” is being offered a replacement. Nikons Service Advisory provides more details, and details on how to claim your free** replacement.

*At time of writing, only 7 cases confirmed worldwide.

**Batteries are only eligible if the 9th digit of the 14 digit serial code is ”F” or ”E”. No other batteries are being recalled, and no other Nikon batteries have been reported as potentially hazardous.

Canon reveals the Canon 60Da for Astrophotography

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Canon has unveiled the new 60Da, an APS-C CMOS 18MP camera. It is a varient of the 69D, only it has been modified for astrophotography, and thanks to a modified low pass filter it can capture nebulae in amazing details. Most cameras have IR filters which limit red light to avoid colour casts, but the 60Da is sensitrive to hydrogen-alpha (Há, also known as red!!

The ionization of hydrogen causes diffuse red light from nebulae, and Canon claims the 60Da can capture this phenomenon in action.

The specs include:

APS-C CMOS 18MP Sensor

1,040k screen resolution

3 in articulating LCD screen

ISO 100-6,400 extendable up to 12,800

DIGIC 4 processor

Modified low pass filter

It can be mounted on a telescope, and uses super-telephoto EF lenses.

This camera is expected to hit the UK shops in June, at a price of £1,174.99.

 

How to create an auto Panorama in Photoshop Elements

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These days, many cameras have a panorama setting, where you have to manually align several images which the camera then combines into a panorama. Sweep panoramas have been invented, all you have to do is sweep the camera from one edge of the scene to the other, therefore improving efficiency and precision.

But for those of you who have cameras that cannot take panoramas? Mr. Photoshop has you covered. Ypu can use the Photomerge auto Panorama in Elements to create a gorgeous panorama.

All you need to do is shoot the images you want to combine, then open them in elements.

Go to file>new>photomerge panorama. You will be directed to a window where you can select your prefernences. Your mode options are shown on the left hand side. Check auto. Select use open images. If you have a later version of elements, you should also be able to select vignette control, and distortion correction. Click OK. The computer will now spend about a minute working on your images, combining them and blending them. Some of the images will be cut out, or layer masks will be applied to help combine the images smoothly, so the image may not be completely accurate. If you do NOT want your computer to do this, go back to your options window and select reposition only.

The edges of the final image will be jagged and seemingly distorted. Select crop tool, and crop these out.

The final image may have visible cracks, but these cannot be een when zoomed to 100%, and they will not print out.

You now have your final panorama. Pleae note that thanks to layer masks, photoshop may edit several parts out of your images to make them fit.

How to use colour curves and levels in photoshop elements

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Levels and colour curves are a great way to adjust tone and contrast in an image. Computer screen have illumination, and so images look rich, but when printed, the image would have no detail. So, levels are a great way to give an image some kick.

Before you start, go to window and select histogram. This will be bring up the histogram which shows the tonal range. A healthy histogram shows a gentle curve, where the tonal range is covered. There should be no ”clipped ” areas, where the histogram shows the blacks, or the highlights bunched up against the ends of the graph. These areas will  print out with no detail.

In Elements, go to create new adjustment layer, and select levels. Ignore output levels, because these remove contrast. Adjust the input sliders, for the midtones, shadows and highlights. Just to check that your images are not over- or underexposed, click the alt key and drag each slider in turn. When colouring appears, you will know that these pixels have been clipped. Once they have been adjusted to your satisfaction, click ok.

There is another way to do it. Personally I prefer levels, becaue i feel it gives me more control, but you can also use colour curves.

Go to Enhance>Adjust Colour>Adjust Colour Curves.

The curves window will then open. You can set a preset, adjust the sliders, and view the effects in the before and after boxes. The graph displays a gentle S curve that shows the tonal range.

The two methods above are very useful for increasing contrast.

 

Diffraction, Limitation and Airy Disks in photography: What are They??

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Diffraction ”Airy Disk” is an optical effect that can really limit the resolution of your photography, no matter how many megapixels your camera may have.

Normally, light travels in straight lines, but can become diffuse (spread out), or diffracted when squeezed through small space, which happens to include your cameras aperture. So basically,  the smaller the aperture, the higher the diffraction. This is why cameras have a sweet spot (when the sharpness is at its maximum) and after that quality degradation can become quite apparent, thanks to diffraction softening and rendering the image.

Knowing your lens’s limits can really help your photography, and avoid you having to compensate for the darkness of the aperture, only to see that the images are unusable. This can be done by setting your camera on a tripod, and photographing a fixed subject at every available aperture. Open them in an editing program, and crop them at 100%. Compare the results, an you will notice that your lenses sweet spot is likely to be somewhere between f8 and f16. Below this, the image degrades, and by f22 of f32 it becomes clear that small apertures should only be used as last resorts.

The finest lenses available are brilliant in every way, but diffraction cannot be completely eliminated. Finest lenses are only limited by diffraction, and so are called diffraction limited.

A digital camera using the bayer array can only collect one primary colour  in each photosite, and in theory, this should allow diffraction to cover about 2-3 pixlels before it interferes with resolution.  In reality, this still interferes with the quality.

DSLRs have larger sensors, so need narrower apertures to create the same depth of field. On the other hand, they can also be stopped down to lower apertures before the effect of diffraction interfere with the resolution, so it balances out. They also generally have a larger aperture range, and the blurred backgrounds they produce is great for portrait photography, and sports photography..

I hope this helped you, it was simply a little scratch in the surface.