RAW

I’m going to shoot three images in RAW and JPEG format to try and discover the differences between the two and the advantages of shooting in RAW. I shoot in RAW already and know a bit about the format. One advantage that immediately comes to mind is that with RAW you can alter settings such as White Balance after a photograph has been taken (using a computer). Another is that RAW files have a higher bit-depth and in theory should be able to capture a slightly higher range of brightness.

Artificial Light (Ring Flash)

JPEG (Camera Processed + Slight Post Processing)White Balance set to Flash

RAW (Processed entirely on computer)

There doesn’t appear to be that great a difference between these two images however it took me much longer to process the JPEG file exactly how I wanted it to look than it did the RAW. With the RAW I simply applied the flash colour balance and boosted the blacks, contrast and clarity to make the detail stand out. The JPEG was more complicated. I increased the contrast and darkened the shadows using Photoshop’s levels tool but this in turn darkened the entire image so I had to also increase the exposure by 1 stop and the saturation as some colour had been lost. The effects I have ended up with are very similar but I prefer the RAW image as it appears stronger and the white area in the background is actually white and not a strange tone like in other image.

Daylight

JPEG (Camera Processed + Slight Post Processing)White Balance set to Daylight

RAW (Processed entirely on computer)

This shot in particular appears deeper in the RAW version. The sky is practically identical in both versions but the main difference is in the grassy area in the foreground. In the RAW version the grass is much lighter but still has a lot of contrast. For both images I selected the grassy area and made adjustments to it. In the JPEG version I had to increase the grass’ exposure yet it is still darker than that of the RAW.

 

High Dynamic Range

JPEG (Camera Processed + Slight Post Processing)White Balance set to Cloudy

RAW (Processed entirely on computer)

I like both of these images, however in the JPEG version the highlight clipped areas look much more harsh. The RAW version is very smooth and it seems that the camera has coped better capturing the highlights in this format. The colour tones are slightly different and I had to reduce the saturation of the JPEG image as it was very bright yellow. I haven’t altered the colours of the RAW version I just darkened the blacks to boost the contrast.

In conclusion the difference between shooting in RAW and JPEG isn’t that drastic. Some problems can occur when applying strong post-processing to JPEG files and if you forget to set your camera to the correct white balance at time of shooting. The main advantage of RAW is definitely the ability to alter the white balance using a computer. RAW files almost certainly capture a higher range of brightness which can be seen in my high dynamic range examples. As for post-processing, extremely similar effects and results can be created by editing either format however RAW is much easier and quicker to edit as the tools are both simple and powerful. Also with RAW, once a setting has been altered, the information is stored in a separate file and so can be altered again without damaging the quality of the image. The more a JPEG image is manipulated, the lower its quality becomes.

My Tolerance for Noise

To test the effects of noise on photographs I am going to take a shot of a single scene at each ISO setting my camera is capable of. Noise is more abundant at high ISOs and so I am expecting to see more and more as I progress from ISO 100 to ISO 3200. I will place my camera on a tripod so the scene is identical for each image, keep the aperture fixed so that the depth of field is constant and won’t use any shutter speeds longer than 1/2 sec as this could introduce another kind of noise.

All of the shots were taken at f/5.6 and lit by daylight coming through a window.

Original Shots

ISO 100 + 200

  

ISO 400 + 800

  

ISO 1600 + 3200

 

Crops

The red boxes on the first image show where I have taken my crops from.

The crops below were taken from the red boxed area on the left of the image above. From these crops it is visible that noise doesn’t really become noticeable until using an ISO above 400. At ISO 400 any noise at all could easily be mistaken for detail. I took these crops at 100% magnification as this is the point at which noise starts to become visible and where it is most accurately differentiated from detail.

ISO 100

ISO 200

ISO 400

ISO 800

ISO 1600

ISO 3200

The shot taken at ISO 3200 is very visibly noisy, however in certain situations this noise could make a desirable addition by giving the shot an attractive grainy effect.

Closer Crop

I have also taken crops at 400% magnification of shots from either end of the ISO range in order to display the drastic difference in quality. At this magnification at ISO 100 there is some slight pixilation but this is not noticeable when the shot is viewed as a whole because it simply looks like detail. At ISO 3200 there is clearly a lot of noise in this shadowed areas and it is very obvious that it is noise because the crop was taken from a smooth part of the photograph and therefor this area contains no detail.

ISO 100

ISO 3200

The noise isn’t a problem if the photographs are only going to be viewed at a small print size e.g. in an album. It is when large prints are required that noise becomes more of an issue.

Noise Reduction

I have added one final image to display one of the powerful tools of Adobe Camera RAW. This tool is the Noise Reduction tool and can be found in the ‘Detail’ tab. I opened the RAW version of my ISO 3200 shot into the processor and altered some of the noise reduction settings to see if I could obtain an acceptable image. I am very pleased with the results however as well as removing noise, the tool has smoothened out some of the intricate detail of the dry decoration. If high ISOs are a necessity but grainy noise is not desired, Adobe Camera RAW’s noise reduction tool is a valuable asset to any digital photographer.

 

ISO 3200 Crop with Noise Reduction Applied

For comparison, here are the ISO 100 and ISO 3200 crops.

ISO 100 + ISO 3200

 

Highlight Clipping

All of the shots below were taken at ISO 200 and at f/11. I altered the shutter speed each time to change the exposure. My camera was mounted on a tripod. My subject is a small ornament of a family of three carved from a piece of wood.

Shot 1 – Highlight Clipping Appears (One stop over exposed) - 1”6sec

Shot 2 – More Highlight Clipping (One stop brighter/Two stops over exposed) – 2sec

Shot 3 – Less Highlight Clipping (Almost non, correctly exposed, One stop darker than first shot) – 0”8sec

Shot 4 – No Highlight Clipping (Another stop darker/one stop under exposed) – 0”4sec

Shot 5 – Again no Highlight Clipping (yet another stop darker/two stops under exposed) – 1/5sec

To demonstrate just how severe the highlight clipping of the brightest shot is I have opened a RAW version in Adobe Camera RAW and taken a screenshot of the image with the clipping warnings switched on. From this image it’s clear that a good portion of the subject has lost all detail.

Highlight Clipping Close-Ups

I took these close-up crops from the back of the child’s head as this area has a very high concentration of clipping.

Shots 1 + 2

 

Shots 3 + 4

 

Shot 5

It is clear that from the shots above, highlight clipping is most abundant in the first two shots. These were the shots that were most brightly exposed. In the brightest shot (shot 2) there is barely any detail and more than half of the crop is pure white. As the exposure time is reduced, more and more detail begins to appear and in shot 2 there is a clear break between the detail of the subject and the lack of detail in the clipped areas. With the lack of detail, there also comes a lack of colour and therefore zero saturation in these areas.

Recovery

Even in shot 3, the correctly exposed shot, there are still areas of highlight clipping. The most aesthetically pleasing shot is shot 4 however it is slightly underexposed and so I will open the correctly exposed shot in Adobe Camera RAW and experiment with the Recovery settings. The Recovery control uses the information from all of the RGB channels to ‘re-build’ the clipped channel. The channels do not all clip at the same time and therefore some of the detail may still be available on another channel.

Original Shot 3 + Recovered Shot 3

Cropped Clips

Original Shot 3 Crop + Recovered Shot 3 Crop

 

Using the Recovery tool in Adobe Camera RAW I have managed to regain some detail in shot 3’s Highlight Clipped areas. The recovered image looks less saturated and much smoother. The highlights are also a lot less obvious and overall it contains much more detail. The recovered version is much more pleasing to the eye.

Sensor Linear Capture

The way that the camera sensor reacts to light falling onto it is very basic and known as ‘linear’. If the light that hits a sensor doubles in brightness then it will be captured as such. This is different to the way film and human eyes work. Eyes and film ’compress’ the light that they see so that double brightness doesn’t appear as great a difference as it really is. Cameras perform strong processing before we get to see the captured image and therefore we don’t notice that it is any different to the scene we’re actually shooting. If this processing wasn’t performed then the image would appear darker than it really is. To see the un-processed image you can shoot in RAW format and then process the image on a computer using a RAW converting software that allows linear processing. To process an image, the camera applies a ‘gamma correction curve’ which normalises the shot’s appearance.

I will attempt to simulate an unprocessed image by opening a JPEG file in Photoshop and applying a curve to darken the shot.

Original Image

I converted the image to 16 bits per channel because using the regular 8 bit mode could cause banding due to the strong adjustments I’m going to make.

Next I applied the curve below to my shot and the resulting image can be seen underneath.

This is what an un-processed image looks like before the camera applies a gamma correction curve.

Next I placed both images side-by-side and viewed their histograms.

It’s very obvious that the (simulated) un-processed image is a lot darker than the original jpeg. All of the tonal values are on the left side of the histogram showing that dark tones are very abundant. In the original (camera processed) shot, the histogram values are all spread along its length with a lot of values at the lighter end of the scale (right hand side).

I then produced a second curve in order to make the image appear back to normal. This is what the camera does when it processes a freshly taken shot. This is a Gamma Correction Curve.

The image below has my gamma correction curve applied to it. It is very similar in appearance to my original image (camera processed JPEG), although still slightly darker but that will be due to my curve not being quite right.

And finally I decided to compare the histograms from the original JPEG and my final gamma corrected image.

Original JPEG

Gamma Corrected with Curve

It is clearly visible that both histograms have a fair distribution of values along their entire scale. The image has a lot of dark tones and shadows thus the high amount of values on the left hand side. Overall the histograms are very similar however not identical as a camera is much more efficient at correctly altering an images gamma than I am. Fro this experiment I have learnt how my camera processes my shots to leave me with well exposed aesthetic images.