Processing Techniques – HDR Workflow

I’ve recently been having an increasing number of conversations on G+ with people who are new to processes such as HDR and wanted some tips and tricks. When I first became interested in HDR Someone was good enough to share their knowledge with me so I thought it was a perfect time to “pass it on”. As a result I will be putting together a few short tutorials on a few photographic techniques, starting with this one: HDR, Using Photomatix.

There are several very good HDR / Tone mapping packages available, I picked Photomatix because I like the interface and results, that’s not to say other packages are not as good, they are but I prefer Photomatix.

HDR Workflow

I tend to use Adobe Bridge for selecting images, note I shoot in RAW almost exclusively and use a tripod for HDR work. Here I have selected 5 RAW files, although the minimum required is 3. I normally shoot at 1EV steps and will take up to 9 RAW’s depending on the light variance and camera histogram. You can use the Photomatix plugin for Lightroom if you have LR and not Photoshop.

Import to Photomatix

Either Drag & Drop  selected files into Photomatix or use the import pictures facility, here you are faced with a couple of pre-processing options and the chance to specify EV values if you have multiple files with the same value. As you can see from the screenshot, you have the ability to select deghosting (manual or automatic), great for windy days and where movement may occur in the image. You can also automatically align images and crop them to match each other, set colour temperature and reduce Chromatic Aberrations and  noise.

Deghosting

If you chose to manually deghost the image (if not why not?) you will be presented with the screen above. The process is simple, use your mouse, tablet pointer etc. to draw around the ghosted areas, as you can see I have selected areas to correspond to the foliage in the foreground and the clouds. Push the Preview Deghosting button to check the effect.

When in preview you can hit the Return to Selection button to add more areas if needed.

When happy with the deghosting hit the OK button to proceed.

Tone Mapping

Hit the button arrowed and the RAW files will be merged by magical pixel pixies into an image ready for Tone Mapping. This is the fun part where the RAW files are analysed and tweaked to produce something approximate to the final image. At this point you will see progress bars on the screen as the images are being processed and combined.

Tone Mapping

Now the real fun starts, along the bottom or side of the screen you are faced with a series of Tone Mapping presets, these are a great starting point and you can select each in turn to see the effect it has. different presets work best on different scenes and to achieve different moods, but as I say they are a starting point. Here I have selected Enhancer Painterly which tends to give a medium amount of processing leaning a little towards grunge.

Also worth noting the pop out Histogram box, I use this all the time to assess how the changes affect the image.

Fine Tune

As I said above, consider the presets as a starting point, the circled control sliders at the left now provide a myriad of options to fine tune the image. You can adjust pretty much any aspect from Saturation & Vibrance to the various lighting effects. Some of the controls I use a lot are Micro Smoothing, white point and detail contrast. Using a combination of these tends to give a more natural looking image whith whites staying white not turning grey, a little POP to the colours and reduction of halos around bright areas. When you are happy with the result, save the file, using File>Save gives the option to save in various formats (I opt for TIFF) and also to automatically export the image to a photo editing suite (in this case Photoshop). It should also be noted that you can save Tone Mapping settings which will be applied as a start point on the next image (great for doing batches taken under the same conditions).

Final Tweaks

Once in Photoshop I tend to make some basic adjustments such as Levels (it’s that histogram again) and localised highlight and shadow control. Dependant on the subject and my mood I may also make some adjustments to sharpness and blur or perhaps tweak saturation or blend in a layer or 2 taken from the initial RAW files.

The Finished Article

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Photography Basics – Aperture, Shutter Speed & ISO

1/6th sec @ f22

1/6th sec @ f22

Welcome to the first in a series of Photography tips aimed at beginners to photography and photographers who have a basic understanding but with to improve their creativity.

I decided to write this as a result of comments online that many DSLR owners used their camera as a fancy point and shoot, when I asked around it was apparent that some people who are new to photography may not have an in-depth knowledge of their camera controls or the basics of photography and that a few simple tutorials may help them to achieve their potential.

I’ll start with the basics as they have the most impact on what we all do in general and also have the most creative impact on an image, that is Aperture, Shutter Speed and ISO.

Aperture

The aperture determines how much light passes through the lens, it is basically a diaphragm that can let in varying amounts of light, similar to the iris in your eye. Fully open and it will let in more light, reducing the aperture size will let in less light, but that is not all the aperture does it also affects the Depth of Field (Dof) in the final image.

DoF is the amount of the image that is in focus on the focal plane, this is basically the point where your sensor (or film) is placed. With the aperture wide open the DoF will be shallow, the portions of the image closer and further away than the main subject will be out of focus and blurred, with the aperture stopped down more of the image will be in focus.

The location of the aperture control on your camera will vary but it will be used to adjust the f-stop or f-number, this number is the ratio of focal length to effective aperture diameter, but a smaller f-number (f3.5) equates to a wider opening and more light / less DoF, a larger number (f16) equates to a smaller opening and greater depth of field.

The actual range of f numbers will vary dependent on the lens in use and you may notice that a zoom lens will have two maximum f numbers i.e. f3.5 – f5.6 which relates to either end of the zoom, finally each change in f-number is one stop or Exposure Value (Ev) in light (remember this it will come up again later).

Shutter Speed

The shutter determines how much light hits the film or sensor, or more accurately, the length of time the sensor or film is exposed to the light entering the camera. On the old wooden plate cameras this was as simple as a wood or metal slide that the photographer would pull out from the film holder and replace after a matter of minutes had passed, as film became more sensitive, the shutter became more advanced offering higher speeds and has now evolved to a series of mechanical blinds in front of the sensor (or film) which open for a fraction of a second to allow light to hit the sensor.

Speeds can range from several seconds to a maximum of several 1000’s of a second i.e 12 s – 1/8000. Shutter speeds also traditionally increase in the following form 1/125, 1/250. 1/500 etc. each increase or decrease in shutter speed related to 1 Ev in light (I said it would come up again).

Again shutter speed has another use, a high shutter speed can be used to freeze motion, that’s great right? We all want the subject to be sharp, right? Well yes, and no. There may be times when you want to convey motion, how do you do this with a subject (or medium) that is static, well by introducing a degree of blur.

Sports photographers will often use a slower shutter speed(1/60th) and pan the camera with the action, when done right this will give a sharp subject but the background will be blurred, a lens can be zoomed during a long exposure to give a creative blur or the motion of a waterfall can be conveyed by turning the appearance of the water into a smooth, silky fog by using exposures longer than 30 seconds.

ISO

ISO is traditionally a rating of how sensitive film is to light, different films would have a different rating i.e. ISO 50, ISO 100, ISO 200, ISO 400 the lower the number (ISO 50) the less grain the film has so it produces a sharper image but is less sensitive to light so needs brighter conditions or a tripod, the higher the number (ISO 400 or even ISO 3200) gives a much more grainy image with possible colour shifts  but will allow you to shoot in lower light.

For example taking ISO 100 as standard; an exposure of f8 @ 1/250 at ISO 100 equates to f8 @ 1/125 at ISO 50 or f8 @ 1/4000 at ISO 3200.

So has the advent of digital cameras made ISO irrelevant? No of course not.

Your DSLR will still have an ISO dial, it will vary between ISO 100 to ISO 3200 on average, and guess what? Each step up or down in ISO equates to 1 Ev (you were paying attention to that – right?).

So what does this mean? Well, in general the Lower the ISO the better. A digital sensor works by converting the light that hits its surface into a digital signal, increasing the ISO increases the sensitivity of the sensor by increasing the electric charge across it, whilst this will allow the camera to work in darker environments it will also introduce noise (or grain) into the image, which can result in a degeneration of image quality. Sometimes, however you may need to sacrifice a little bit of image sharpness to get the shot, indoors at a concert or sporting event the lighting may not be bright enough without increasing the ISO, or you may want to use grain creatively.

The Exposure Triangle

Now, if you remember what I wrote earlier there is a common point: each increase or decrease of Aperture, Shutter Speed and ISO increases or decreases the Ev by one stop, therefore a combination of these values will give a correctly exposed photo but with varying effects. If you want just a small part of the image in focus a wide aperture will achieve that but will require a high speed, if you want more of the image in focus use a smaller aperture but you will need a slower speed, this is the basics of making a manual exposure (that funny M symbol on the camera settings).

Most Cameras will have at least a program (auto) mode, Aperture Priority mode and Shutter Priority Mode. Program will do a decent job at getting a well exposed image, but use the other modes and play. Taking a portrait? Open the aperture a bit (to f3.5 for example) and throw the background out of focus. Shooting a landscape? Close the aperture down more (to f11 or f16) and pack the frame with front to back sharpness. At a sports event? Set the camera to Shutter Priority and use a high speed (1/500th ) to freeze motion or use a slower Shutter Speed and deliberately add blur to emphasise movement.

Photography, as in life has rules; rules to get the right exposure, to freeze motion, to obtain the most pleasing composition. I would urge everyone to learn the rules and learn when to apply them for best effect, in this way the technical aspects of photography becomes second nature and will allow the photographer to concentrate on the creative aspect of photography. But just as importantly, or more importantly, knowing the rules means that when you deliberately break them, you know why you have done so, you will have done so for a creative reason, but you will also know how to reproduce the effect when you need to.