This article is a summary of months of trying to discover why some of my images did not look very good after resizing for web viewing. I described it as Unsharp images. I discovered it had nothing to do with sharpness. I mention a long period because this has been a little thorn in my side for about the six last months. I would try to find an answer, never got anywhere, gave up for a while and would try again later. I finally became very frustrated about three weeks ago and immersed myself into finding out what's going on. It did not help that I spent a fair bit of money on two Photoshop courses (Level 1 and 2) and both the instructors gave me the same answers. Then it occurred to me they are teaching Photoshop and they will give the standard answer. This did not in any way cost me from getting on the front page at DIC, nor am I trying to say that members have poor images. Composition, creativity, what story your photo has to tell will always beat out a sharp boring picture. This was just something important to me and I needed to know the answer.

The culprit turned out to be, to coin a term "mass downsampling". As we increase in mega pixels we can print bigger better quality images. What happens when we reduce the size of an image? As we reduce the size of an image some of the data has to be removed. This involves complex mathematics called algorithms. Every software manufacturer has their rocket scientists to figure this stuff out. How this data is removed varies from software to software and like anything else every one affects the final image. Also less information has to be removed from an image taken with 3 megapixel camera as compared to an 8 mega pixel camera. A resized 3 megapixel image will look closer to the original image size. If you have an 8 megapixel camera and you shoot on medium or low quality the resized image will look closer to the original image size. Less resolution = less information to remove.

Photoshop on its own does not do the best job of resizing images. My instructors and other sources always stated when reducing your image in Photoshop use Image Resize, set your Resolution to 72 , select your final image size (ex 800 by 533) and select Bicubic Sharper. I can't back up what I have to say next using math, etc it's just what I learned from people that I will say "understand this stuff at the molecular level". I can only tell you I am convinced it's true. These gurus state you should never use Bicubic Sharper. Bicubic Sharper is destructive. You should use Bicubic Standard. I'm not sure what the community has to say about that but I decided to brave that one. Open one image, duplicate it, reduce one with Bicubic Sharper and then try the other one with Bicubic Standard and look closely.

Even using Bicubic Standard in Photoshop on its own is still is not the best for resizing, however it can be tricked. I will get into that later. On my road to discovery I came a across many resizing plugins, actions and stand alone software developed by companies, pros and amateur enthusiasts. It would have been easier for me long ago if they had called them, "Downsampling with a Minimum Quality Loss Followed by a Wee Bit of Sharpening". For example I recently downloaded the trial version of Photokit Sharpener. It has three features, one to replace missing data from digital transfers, a second for creative sharpening and a third for web viewing. The web viewing feature worked very well. Overall I think it would be great for professionals and serious hobbyists who do a lot of creative work and printing. I'm not promoting this product, it's just an example of one that's out there. It is a little pricey for my needs.

Photoshop can be tricked. I discovered many people brewing up their own cocktails. It's a bit of a Black Art. One method resizes and sharpens in increments. Another sharpens at full size and uses a luminance mask after resizing in one step. Although there are several approaches they do produce similar results, they work well and are all free. All use Bicubic Standard when resizing. I like these three. Just a note the standard abbreviation for Unsharp Mask is USM.

Pacific Northwest Nature Photographers Tips, Tricks, Techniques & Tutorials

Sharpening Techniques

• Take full res image and reduce size to between 1000 and 1300 pixels. As much as 1300 for detailed forest scenes and such, 1000 for rock and more simple images. Apply "Sharpen" filter (easy enough right?) twice or even three times at 1300-1600 pixels.
• This will create a very oversharpened, noisy, mid-size image.
• Further reduce image size to your web preference.
• When reduced, this "tricks" Photoshop into applying an ultra-fine USM that you simply cannot achieve through other methods and all with maybe a 5-10% increase in file size vs. traditional methods such as regular USM or PK sharpener - which is rarely a problem.
• Play around with this technique and make it work for you. Every image is different. Sometimes I'll apply a sharpen filter 3 times at 1500 pixels and then reduce for an even finer sharpness, but other times it has too much of an adverse effect on color and re-saturation is necessary. Sometimes I'll just lasso an area and apply the filter more heavily in one section before reducing size. Just experiment!
• Last, keep in mind not to sharpen skies too much as this will unnecessarily increase file size. Do local touch-ups with 'sharp brush' to improve textures/definition in sky and water!

This is a very simple method and it produces great results. He jumps around a little in the first paragraph but you get the point. What I do here is reduce to about 1300 (sometimes 1600), sharpen twice USM @ 100 0.05 0, then resize to web view. I have also applied another light Sharpening pass with a different sharpener after completion just to finish it off. You can use Photoshop for that. Experiment!

Manyk SRS method

Another example is the Manyk SRS Photoshop action which does a very good job that I have posted in the members chat threads. I like it because it does three final USM passes and you back up to select at what point you like the image.

Alternate Method

1. Sharpen your image at full resolution using your favorite sharpening method.
2. Downsize in a SINGLE stroke using standard bi-cubic to (ex 800 by 533)
3. Duplicate Layer and set to "Luminosity"
4. Exclude (0-32) and (216-255) tonal ranges. This prevents over sharpening highlights and shadow areas to maintain detail.
   • right click on the image in the layer mask
   • select blending options
   • find the "this layer" slider
   • while pressing the ALT key drag the left pointer (it should split) until it reads 32
   • repeat with opposite slider until it reads 216
5. 3 x USM @ 50 0.3 0 sequentially, one after the other.
6. Flatten image.

I found this method does very good job of maintaining detail.

Some Light Reading

Finally if you are interested in pursuing this even further here is an excerpt from one of the threads I read. "Just a suggestion, buying the new book by Bruce Fraser - Real World Sharpening with Adobe Photoshop CS2 would be highly recommended. I would put Bruce Fraser as one of the top three Photoshop Guru's of all time". I don't plan to read this myself in the near future but with my luck he will probably say to use Bicubic Sharper. Bruce Fraser is with the group that developed Photokit Sharpener. I believe Marc Adamus gives that sharpener a bit of a jab in his blurb. Oh well. This is what makes things interesting.

Summary

As stated there are many different methods and approaches to this. Some of you may have not have noticed this or any difference. You may be using a good sharpener/resizer already. If you try it using a "still life" image with fruit that fills the entire scene it will not be as noticeable. You will notice it in scenes with trees, brick walls, fences, etc that are at a distance. Every image is different. I plan to use all three for different situations. One last thing you can try. When you have completed your resizing and sharpening, apply the polishing step USM @ 10 20 0 and watch your image pop. It is similar to applying curves and I have added this step to my downsizing actions. You can easily create actions to suite your taste. Brian Watters has developed a great visual tutorial on how to do this. I have been having a lot of fun doing that. Hope this helps. It sure was an eye opener for me.