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Archive for the ‘Digital Photography’ Topic

2017.06.05

Nearly all digital cameras, including all DSLRs and nearly every mirrorless ever made, show a view recorded through the lens. By definition, DSLRs use an optical viewfinder which makes it the easiest to see subtle changes in the view when using filters such as a polarizer.

A Circular Polarizer, further referred to simply as Polarizer, is a special filter which filters out light with a certain polarization. It is used to diminish the effect for haze and reflection which results in increased saturation when taking photos of nature. When shooting through glass, a polarizer helps see more clearly by reducing surface reflections. Here is an unpolarized shot of the Cotopaxi:

First is to know when to put it on and when not too:

  • It is not advisable to keep a polarizer on constantly, although some people who do that, because usually reduces light by 2 stops. The only exception to this are Hoya HD filters which reduce light by just one stop. This forces the camera to either use a slower shutter-speed, which makes things that move blurry, or higher ISO which makes images more grainy.
  • Polarizers are not useful in dull or diffuse light. They only have an effect when the polarization of light differs sufficiently.
  • They are useful in bright directional light and you should see the effect right away when it is. Even in bright light, their effect is strongest at 90-degrees from the sun. If you are shooting into the sun or directly away, there will be very little difference.
  • Polarizers are not recommended for ultra-wide-angle lenses, due to the previous point. Specifically, if the scene being photographed includes light that is parallel and perpendicular relative to the sun, the polarizer will only affect part of the light and results will look very strange.

Here is the same scene of the Cotopaxi taken with a Hoya HD Circular Polarizer mounted:

Note how details are more visible on the side of the volcano. There are also more details in the snow-covered area which are highly reflective. The biggest difference in this scene though is a change in color. The sky blue is actually caused by light bouncing in the air between water and dust particules. When the polarizer is in effect, a notable proportion of the blue goes away, making vegetation look greener and more saturated.

Second is how to use a polarizer:

  • Looking through the viewfinder, frame your shot, zooming if necessary, then rotate the outer ring of the polarizer. Make sure the filter has been screwed sufficiently tight. Otherwise, you’ll unscrew the whole thing and it can fall to its death.
  • Rotate the ring until you see the most pleasing image. Generally the sky gets darker to a point and then start brightening up. At the darkest point, the effect is maximal but you may not want to go that far if it makes the scene look unnatural, such as the sky being much darker than the foreground.
  • Polarizers also remove reflections. If that is the goal, rotate the ring until you see the least reflection where you want it to go away. It is rare that it disappears entirely unless the surface is completely flat.

Here is the final shot of the Cotopaxi with the Circular Polarizer rotated to maximize its effect:

One can see here that there are more details throughout the image and that colors appear more natural. Another thing to note is that all images are about the same brightness despite the polarizer cutting down light significantly. In all these cases, the camera has set to Aperture Priority mode with the aperture set to F/6.7. Since these were captured using a 250mm lens, the shutter-speed stayed at 1/250s for all shots. Auto ISO was on though, so the camera took the three shots at ISO 200, 400 and 800, respectively. Without Auto ISO the camera would have changed the shutter-speed, potentially causing some blurring. For those shooting in Manual mode, one must change a parameter manually to compensate for the loss of light.

Finally, it is completely worth investing in a quality polarizer. The effect cannot be replicated by software and a poor polarizer can introduce flare. The Hoya HD series not only transmits more light then competitors, it is also made of hardened glass which protects it from impact. They are also coated with a water and grease repellent layer to make cleaning easier. Currently, the Hoya HD3 is the cream-of-the-crop of polarizers. Just make sure to get the right size!

Neocamera Blog Neocamera.com © Cybernium

2015.05.18

To keep or delete? is one of the two eternal questions in digital photographer. The other, unsurprisingly is RAW vs JPEG? which is wormhole of its own.

Of course, this is a personal question and it varies tremendously. Some situations, like fast-moving actions almost guarantee a higher hit-to-miss ratio, so there is no exact numeric answer to what percent of images to keep vs delete.

Puebla Cathedral

 

Finding Keepers

My motto for this is Delete is my friend 🙂 First, I delete anything that is not technically perfect, making extremely few exceptions (less than 0.01%) for moments which give emotional attachment. Say, the first step of a baby, even blurry, is probably a keeper! Then, it is time to and then delete anything that has no point of interest or is too similar to another shot.

A great exercise is to give yourself a the challenge to simply not shoot the bad ones. It has been working for me, diminishing my deletion ratio is while augmenting the quality of my shots. Now, I am below 80% deletion. From what’s left, only 10% get shown, either off or on-line, and about 4% get sold as prints or licensed to publications.

The most common reaction is that storage is cheap and I agree, only the cost of managing storage is not.

Workflow

Here is a workflow that works to efficiently reduce the number to store:

  1. Delete immediately in-camera missed shots. Things like people entering the shot at the wrong moment, forgot the camera was in MF, etc.
  2. Delete anything that is not technically perfect: sharp, focused, well exposed, well framed, correct WB, level, etc as a first pass on the computer. PMVIew Pro on Windows and Geeqie on Linux are most efficient for this.
  3. Delete everything that is too similar, keeping the best of course. This is the second pass on computer, also with the same fast viewers as above.
  4. Import into Lightroom, apply keywords and rank as the third pass. This is when documentary shots that lack interest get ranked low. Lightroom has a 0 to 5 start ranking system which is reasonable granularity. Most DAM Software offer something similar. My personal ranking is:A) Zero stars for things that are not pictures such as panorama pieces or brackets for Exposure Fusion or HDR.B) Things that are technically reasonable but lack interest get 1 star. Try to crop them and see if they get more interesting, in that case they can be upgraded to 2 stars. If they show a technical error, also rank then with 2 stars.C) A technically perfect and interesting photographs gets 3 stars unless:

    D) It is also evocative and would make an appealing print in a visible location. Album prints do not count, those are more for souvenir-type images. In this, rank with 4 stars unless:

    E) There is NO way the picture could have been improved by a change of position, framing or camera settings. In that case, it is ranked a full 5 stars.

Puebla Restaurant

Improving

The goal, while repeating this process after every shoot, is to stop shooting the 1-3 stars images. This is what will make the ratio of keepers constantly improving. Always ask yourself why something came out poorly and what were you thinking at the time. Always tag anything that got cropped (or worse 😉 ) to known each time when you failed to do things properly.

Closing words from Jay Maisel:

“If you are not your own harshest critic, you are your own worst enemy.”

Neocamera Blog Neocamera.com © Cybernium

2013.11.23

Now that CMOS sensors are incredibly common, even on ultra-compact cameras, many digital cameras can quickly capture multiple frames to produce a single image which cannot be captured in a single shot. Even if the camera cannot do it, software exists to combine multiple images together in different ways.

An exposure is what happens in the camera from the time the shutter opens to the time it closes. Most images are produced from a single exposure which takes a slice of time and dynamic-range and captures it. By taking multiple exposures and combining them, one can produce an image which shows more than what an exposure can capture.

Multiple images can be combined in a number of ways:

  • Panorama Stitching – This produces an image with a wider field-of-view than any individual image can, up to 360-degrees actually.
  • Exposure Fusion – This averages out pixels from different exposures to produce directly a low-dynamic-range image, so there is not need to do the tone-mapping like for HDR images. Tone-mapping is the delicate operation where, without a subtle hand, you end up with the types of images you are talking about.
  • HDR Blending – This takes images from multiple exposures to produce an image which stores more dynamic-range than what the camera can normally capture. These images are often used in 3D rendering to make simulated reflections more realistic.
  • Focus Stacking – Takes images focused at different distances to produce and image with an impossibly deep depth-of-field. Often this is used for macro photography to show entire subjects in focus.
  • Image Stacking – This is one most often used with astrophotography. This creates a long exposure by adding up short ones. You would need to take 525 consecutive exposures and the Image Stacking software will blend them into one.
  • Multi-Frame Noise-Reduction – Averages a number of images to produce one which is less noisy. This can also be used for astrophotography to reduce the noise in long low-light exposures.
  • Multiple-Exposure – Overlays multiple images to artistic effects. This is what layer-blending in Adobe Photoshop essentially does. It shows images as if they were super-imposed.

Note that you can combine techniques which requires even more images. For example, to produce an image which captures a wide dynamic-range and infinitely deep depth-of-field, one may use 5 shot brackets at each focus distance. With 5 such distances, one would need 5 x 5 = 25 shots.

Some artists take this to the extreme by using different combinations of multi-exposure techniques for foreground, middle-ground and background elements and then blending the results together which is yet another similar technique. Images combined from hundres of exposures have been produced!

Neocamera Blog Neocamera.com © Cybernium

2013.07.15

Nearly every digital camera on the market, even most point&shoot models, offer a choice of metering system. This deceptively simple option can completely alter the result of images. Luckily for many compact cameras and a number of mirrorless ones, the LCD or EVF correctly previews the effect of the currently selected metering mode. For DSLR users, it is harder and you need to become familiar with how metering modes behave. Naturally, the question is: When to use a particular metering mode?

Every digital camera has a Multi-Segment metering mode. Nikon calls theirs Matrix. Canon calls theirs Evaluative. They work the same way except that each has its own secret formula. In fact, even different Nikon cameras have different Matrix modes. These modes are generally targeted to the intended users of the particular camera. So a lower-end Nikon tends to produce brighter images compared to a higher-end model under similar conditions. These Multi-Segment modes are very sophisticated and does a good job in most situations.

Spot is used when you know what part of the scene is going to be your midtone, that is the part of the scene that you want to show as 18% luminance which corresponds to a middle tone, hence the term midtone. This is simply based on an old research which concluded that the average scene reflects 18% of light that falls on it.

To use Spot metering, you must point the spot meter at that part and lock the exposure using either the AE-L button or by half-pressing the shutter. Most cameras are setup like this initially but you can change that on certain models. Then, you reframe your subject without releasing the shutter or AE-L button and take your shot. When using the Spot meter, nothing else is considered by the chosen spot.

Many Olympus cameras feature also Highlight Spot and Shadow Spot options. These work similarly to spot except that they meter for a highlight or shadow, respectively. These are generally more convenient to use since it is easier to tell which part of the scene is brightest or darkest, than to tell which one falls in the midtone. Users of other cameras can use Spot in conjunction with Exposure-Compensation to achieve the same exposure. Dialing around -3 EV of EC gives a shadow spot while dialing around +3 EV gives a highlight spot. The exact amount of EC needed depends on the camera’s dynamic-range which is itself dependent on the selected ISO.

Center-weighed is basically the ancestor of multi-segment metering. It tries to make the central part at least 18% bright but will vary the results depending on the brightness of the surrounding areas. Average metering is also simple in that it simply averages several measures which are evenly distributed across the frame.

In most cases, selecting a metering mode to use is easy:

  • Use Spot metering when you know which part of the scene should be your midtone.
  • Use Multi-Segment metering otherwise.
  • Use Center-Weight or Average when Multi-Segment fails.
  • Adjust with EC as needed. No metering system is perfect yet!

Neocamera Blog Neocamera.com © Cybernium

2013.06.17

Blurry images are caused by many things. The most common cause is probably photographer movement. This is exaggerated by high-resolution sensors such as the one on the  just reviewed Nikon D7100, long lenses and dim apertures on typical kit lenses or high-magnification ones.

For better stability while shooting hand-held, turn stabilization on and use this hand-held shooting technique:

  • Assume a stable posture, usually not leaning in any direction.
  • Support the camera’s weight with the left hand.
  • Grip firmly with the right but let the index-finder loose.
  • Press the shutter-release halfway and wait for a focus-lock (When using AF)
  • Breath in
  • Exhale
  • Gently press the shutter-release fully.
  • Wait for the photo to be taken (Most people skip this step)
  • Resume breathing.

A tripod is always best for stability but they can be quite cumbersome, impractical or outright forbidden is some places. Depending on the weight of your camera, a Gorillapod can possibly do. It is a small, cheap and relatively light (How often does that happen?) flexible tripod.

Neocamera Blog Neocamera.com © Cybernium

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