Matt Spinelli Photography - RAW Photo Editing with s7raw

By Matt Spinelli, 9/26/2005

Do you wish you could get more resolution out of your photographs without having to purchase a new, higher megapixel, digital camera? Do you long for more control over your photographs? Well then, have you heard of RAW capture and RAW photo editors? It is all the more common for digital cameras to offer RAW modes for capturing photographs. Nowadays this feature isn't limited to expensive Digital SLR cameras. RAW capture can be found on cameras costing as little as $300 (US). RAW photo editors are also easy and inexpensive to obtain. In this article we will look at a free program called s7raw (product website here). What advantages and disadvantages are there to using RAW capture verses using JPEG? How do the final results of editing a raw photo compare to editing a JPEG photo of the same subject? What are the pros and cons of using the s7raw photo editor?

Why Use RAW Mode?
For everyday use the best quality JPEG mode is just fine for digital photography. However, times may exist when we may want a little more 'oomph' out of our digital cameras. Perhaps a detailed landscape or a sentimental portrait is the subject we want to photograph. Why would RAW mode be better suited than JPEG? First, RAW captures are lossless. Nothing is lost when making the digital file. JPEG on the other hand will throw away 83-92% (compression ratios 6:1 to 12:1) of the original picture before saving to the memory card. Most of the time it is hard to see a difference, but upon close inspective, or if you want to print at large sizes, the compression can be very noticeable.

The second advantage, and perhaps even more important, is in order to obtain a RAW image the digital camera will by pass all of it's processing to give you an untouched image. Not only is there no compression, but also the image doesn't have any sharpening, noise reduction, color adjustment, or other digital manipulations applied to it. This may sound like a disadvantage but it really isn't. RAW mode will give you the opportunity to make these adjustments as you see fit. You will have more control over how the photograph is processed, and ultimately, what the photograph will look like.

There is even a third advantage. Many RAW images have 12-bits per color whereas JPEG have only 8-bits. A 12-bit image has 4,096 different brightness levels. A JPEG image has only 256. Why does this matter? When adjusting things such as levels, curves, and colors in a photo editor it will throw out some of these brightness levels. If too many are thrown out (i.e. many edits are preformed) the darker areas of the image will begin to have a banding or posterization effect. Below is an example of posterization. By using the RAW format you can reduce the chances of this happening.

Posterization
s7raw photo editor posterization

No Posterization
s7raw photo editor no posterization

There must be some disadvantages right? Since RAW files are uncompressed they take up more space. A high quality JPEG from a four-megapixel camera may be around 2MB whereas a RAW file will be around 8MB. So if you shoot in RAW mode plan on having a few extra memory cards around. Also some cameras will not let you use burst modes with RAW files since their internal buffers cannot process the larger files fast enough. Not to be overlooked is the fact a RAW file has to be processed before it can be used. This can take hours if you have taken a lot of photos.

Comparing Results Using s7raw - Test One
Now we can finally discuss the s7raw photo editor. In this article I will compare two sets of photographs of a natural subject and a resolution chart. Each subject has been shot in both RAW mode and the highest quality JPEG mode found on my Fujifilm FinePix S5100 digital camera. Each set of photos was taken under the exact same conditions and with the same settings.

To start, above you will see a screenshot of the s7raw program. The picture is the first test subject, a fallen rose. It is beyond the scope of this article for me to get into all the features of s7raw, but I will explain how to convert the above test image to the final photograph. If you look at the screen capture it is evident that s7raw is not the easiest program to use. However, it offers a wide array of customizations that can be preformed. For this test I am primarily concerned about fixing this underexposed image. To do this I will first adjust the white balance to be incandescent since I took this shoot indoors with normal lighting.

Next I go to the lens tab to fix the slight vignetting.

s7raw photo editor vignetting correction

Then I head back to the Adjust1 tab and set the Red, Blue, and Green sliders under the fine-tune check box to make each channel's histograms expose properly.

At this point I could adjust the gamma, contrast, brightness, saturation, hue, sharpness, moiré, curves, chromatic abbreviation, and selective color manipulations. But I will leave this tutorial to just white balance, vignetting, and histogram adjustments. I plan to explore the other options in a future article. At the time of this writing s7raw version 0.4 allows for saving in both 8-bit and 16-bit Photoshop and tiff formats. For this comparison I will only use the 8-bit Photoshop format, as it will make it easier to compare to the JPEG test. Once converted the only adjustment I make in Photoshop Elements is unsharp mask in an effort to make the RAW photo as sharp as the JPEG image (I prefer the sharpening found in Photoshop compared to s7raw).

With the JPEG image I use Photoshop Elements and will adjust the histogram for each channel and the lens vignetting (using the PTlens 6.3 plug-in) to get the photograph as close as possible to the RAW photo. Since the camera applied it's own white balance I will not adjust that aspect of the photo. It was also apparent that the in-camera processing added more saturation to the colors so I had to reduce some of the saturation to bring it close to the levels found in the RAW image. So what was the result?

Final Raw photo (resized for screen viewing)
s7raw photo editor converted image

Final JPEG photo (resized for screen viewing)
JPEG converted image

So what is different? The vignetting is still noticable on the RAW image, but that is my fault and should be ignored. When viewing the image as a whole like this the differences are subtle. One thing you might notice is that the subject looks smaller for the RAW photo. The reason is that I resized both files to be a maximum width of 500 pixels. With my S5100, when shooting in RAW mode and using s7raw, it actually gains some physical resolution. The full size RAW photo was 2302 x 1734 pixels (3.99 MP) and the JPEG was 2272 x 1702 (3.87 MP). As such, shooting in RAW mode on a Fuji S5100 creates a resolution gain between 1.3-1.9%. As a result, when resizing to the same width as the JPEG photo this creates the illusion of smaller image.

Does this mean there isn't an advantage to using the s7raw, or RAW modes for that matter? Let's look at a few 100% full zoom crops to find out. Be prepared though that the difference will not be gigantic.

RAW Leaf Crop
s7raw photo editor leaf close up

JPEG leaf Crop
JPEG leaf close up

Besides the difference in color, you should be able to notice that the veins of the leaf are more detailed in the RAW photo. Especially is this the case when looking on the right side. Some portions of the JPEG photo are a little smeared. Lets move on to another area.

RAW Flower Crop
s7raw photo editor flower crop

JPEG Flower Crop

Look closely and you'll be able to notice that the RAW file has a much smoother look to it. Both images are sharp but the RAW photo has fewer artifacts in the image. Also noteworthy is the lines on the flower are more defined in the RAW photo than compared to the JPEG.

Now that you have seen some of the physical differences that can be viewed on a computer screen let's look at one of the biggest differences between the two formats. To do this we have to look at histograms again.

RAW Histograms
s7raw photo editor red histogram

JPEG Histograms
JPEG red histogram

The histograms for the RAW image are smooth whereas the JPEG image contains a comb-filtering effect. The jagged histogram of the JPEG image isn't desirable because it means that the photo has less variation form one brightness level to the next. In extreme cases this can produce color banding to appear when printing. At best it reduces how much processing can be applied to the photograph and thus limiting the potential of the JPEG image. Since all the manipulations to the RAW file were done in s7raw, which processes the files in a 16-bit color space before saving the image as an 8-bit file, there is no banding or posterization found in the RAW photo.

Test Two
The second test I did with s7raw was to use a resolution chart. Please understand that this test wasn't designed to find the resolution of the camera but simply to compare the differences between RAW and JPEG. We will look at both the horizontal resolution and the vertical resolution. The goal is to see if more detail can be resolved from s7raw and using RAW mode than when using the in-camera JPEG mode. For this test no manipulations were done to the files except a slight unsharp mask on the RAW image and some color adjustments on both files in Photoshop. For this test resolution will be determined by finding the point were detail is no longer found and where multiple lines blur together. The below images are at 200% crop.

RAW horizontal Resolution (detail to ~1700 lines)
s7raw photo editor horizontal resolution

JPEG horizontal Resolution (detail to ~1550 lines)

RAW vertical Resolution (detail to ~1700 lines)
s7raw photo editor vertical resolution

JPEG vertical Resolution (detail to ~1550 lines)

In both sets of crops the RAW photo benefited form a near 10% gain in resolution. Earlier I mentioned that shooting in RAW mode provides around 1.5% more physical resolution, however that doesn't factor into this test since the additional physical resolution is actually added outside the frame which means the crops above are the same exact size. The gain in resolution from using RAW verses JPEG is comparable from upgrading a 5-megapixel camera to a 6-megapixel camera.

Pros and Cons of Using s7raw
s7raw has many things going for it. The software is a beta program and is still being improved upon. All indications point to s7raw as being freeware for future versions. I find it amazing the number of adjustments and customizations that can be done with s7raw. The fact that the software can produce a near 10% gain in resolution in my test and produce more dynamic photographs is very commendable. Some have mentioned that it doesn't handle diagonal lines near 45 degrees well by creating a step effect instead of a smooth line. I have not found this to be the case with the camera and version of the software that I use. Below is a 45-degree angle with both the RAW photo and the JPEG photo at 100% crop. As you can see there doesn't appear to be any stepping effect.

Raw diagonal
s7raw photo editor diagonal test

JPEG diagonal
JPEG diagonal test

The only negative thing I have noticed about s7raw is that it appears to add artifacts into the image. These are small random looking lines that appear in detail areas of an image. Below is an example from the resolution chart at 400% crop. There should only be horizontal lines in the image but yet some vertical artifacts appear.

Conclusion
Using s7raw along with a digital camera's RAW mode can increase image resolution, provide cleaner, more dynamic photographs, and allow for processing to be done in multiple ways by the photographer instead of the camera. I use s7raw because of the sterling results it provides and would recommend it to anyone looking for a free, powerful, RAW editor.

Go to s7raw User Guide and Tutorial