Posted by: In: Books, Guidebooks 06 Mar 2013 1 comment Tags: , , ,

I spend a lot of time reading. At times, I come across a book that is really well written, as well as informative and useful.

Bryan Peterson’s book – Understanding Exposure, (3rd Edition) is a testament to this ethos, and is simply genius in its descriptive ability to draw the reader in.

As a photographer of a few years now, I have been to evening classes, and spent a lot of time on photographic forums, picking up bits and pieces here and there, but nowhere have I found a book that so simply breaks down the photographic process as this. Even taking an A-Level didn’t educate me as well!

The author somehow takes the most simple of sentences and continues to draw the reader in. It’s almost as if you’re understanding it as you read it without actually knowing that you get it. It’s like a fine ale (if you’re a beer drinker) or good quality chocolate (if you’re a woman), or the Book Of Answers if you’re a photographer.Understanding Exposure at Amazon

I’ve been sat here a while now, thinking of ways to describe just how useful this book is, but sitting back and looking at realms of (now deleted) text, I wondered how useful that is to you, as a potential buyer.

I thought I knew it all, and to be honest, in my cluttered mind, I did know a fair bit. But this book sets everything into a logical order, and explains it with such childlike simplicity and clarity, that I found myself re-learning everything again, only this time, in the proper order. And to an engineer like myself, I was being told why I was doing it that way. Sometimes, once you grasp the concept of “why”, the rest all falls into place. A bit like the magic of hyperfocal distance…

Photography is all about exposure. The amount of light hitting your sensor/film. That’s it. It’s about obtaining that balance. It’s about how to manage/juggle shutter speed, ISO and Aperture to get the right exposure for you. And the emphasis is always on the last two words there. For You. And that’s another great thing about this book. It isn’t about telling you what to do to make a great photograph. This is about equipping you with basic fundamentals to allow you to make a great photograph. There is a huge difference.

As an example, I always used spot metering to evaluate the exposure in a scene. I didn’t really know why, I just did. I pointed the spot at my subject, took a reading, recomposed, then took the shot. That’s fine in most circumstances, but there are forms of photography where it’s not so clear. A sunset for example, or a long range shot of the moon. Within these pages, the explanation is so clear that it’s obvious where you need to meter from in order to take such a shot.

I read this on holiday. And spent a lot of time shaking my head in wonderment as things were explained to me that I really hadn’t bothered with before. But these things were explained with such simplicity, it was more a wonder of how I managed not to “get it” before.

If you have a few quid in your wallet, spend it on the shopping and order this on your card. No matter what level you’re at (professional photographers excluded!) you’ll find this book brilliant.

The book itself is a big glossy softback with some lovely images inside. It’s also got some bad ones too that illustrate how not to do it. The first few chapters are devoted to absolute basics and defining the “Exposure Triangle” of Aperture, Shutter Speed and ISO. These three ingredients are key to understanding different aspects of an image. Peterson tackles each of these three subjects in depth and explains what happens when you have high or low variations of the three options. By understanding what to expect with an Aperture of (for example) 2.8 or a low shutter speed of 1/20 second, or a high ISO of 1600, you as a photographer can elect to make these changes secure in the knowledge of what the effect will be on the final image.

The last major section of the book talks about light itself. This is an unusual chapter and really opens ones eyes to the way light falls on subjects, and how important it is to be able to recognise this. Different types of day and different types of weather can drastically affect how light falls on a subject. My 52 challenge this year is an exercise in learning about light. The same subjects all year round, but images taken in different lighting conditions and at different times of the day can dramatically effect the outcome. The most important aspect of this book is its ability to break down what might first appear quite complicated and make it seem simple. Even now, it still makes me smile when I read it.

Last of all, there is a section about special techniques. The use of filters, multiple exposures, HDR and flash are all discussed within the premise of the previous content. It’s a nice ending to a book that should be on every amateur photographer’s shelf. Well worth the investment!

Thanks for reading!

Ian

What is High Pass Sharpening?

Every digital image you capture records the scene in front of you depending on the settings in your camera. The sensor measures the light hitting the cells and the camera processor turns this into an image. Depending on how you shoot, it might be heavily processed into a JPEG file (if you shoot in JPEG format) or it may be lightly processed into a RAW file. Either way – the important fact to remember is that it is processed in some form.

Once you review the image at your leisure, you may decide that it’s not sharp enough and want to do something about it. Some reasons for lack of sharpness are:

  • Missing the focus point: Maybe you hit the portrait subject’s ear instead of their eye and the eyes are a bit blurred.
  • Poor lens quality: Some lenses are not as good as others and things like edges of photographs can sometimes be a bit blurred, especially on wide angled lenses.
  • Lens out of alignment: Maybe your lens is faulty?
  • Not sharp enough: Maybe the processing in-camera (either RAW or JPEG) didn’t sharpen the image enough for you.
  • Movement: You moved during the shot and blurred it.
  • Aperture: Some lenses are considered to be “soft” at their widest apertures. (f1.4 for a 50mm f1.4 for example, or f2.8 on a 70-200 f2.8 lens)

Software can take care of sharpening for you. Lightroom has excellent sharpening tools for example, as does Adobe Camera RAW. However the High Pass sharpening method (in Photoshop) allows you to have a degree of control not only of how much sharpening you apply, but where it is applied too.

So you can see for yourself, here is a landscape image that was a hand-held HDR, so there is a blur to the branches of the tree (you may need to do a page refresh to see the image whilst I iron out some creases). Drag the slider (or just click on the image) to see how sharpening has improved definition in the tree branches but hasn’t affected the sky or foreground.

 

 

High Pass Sharpening In Photoshop (CS5): The Process

The process is very simple and has a lot of flexibility.

  1. Open your image in Photoshop
  2. Duplicate it with CTRL+J
  3. Click on Filter>Other>High Pass. This should make everything go grey. Don’t panic. The pop up box should be asking you for the pixel radius. Now, the radius you set and the effect it has will depend on your overall image size. You want to adjust the slider so that the edges are peeking through the grey. For my 50D which has an example 5000 x 3000 pixel image, I tend to use a radius of between 3 & 5 pixels. On lower resolution images though this will have a more pronounced effect.
  4. Change the Blending Mode from “Normal” to either Soft, Hard, Vivid or Linear light. “Soft” will give a much more delicate effect. Linear light gives a very pronounced effect. I find “Hard Light” to be the best “middle ground”.
  5. (Optional) Reduce the Opacity if you need to. This allows you that last degree of control over the whole sharpening process.

That’s it. Dead simple.

The last step is another optional one. In y example image above, I have just applied sharpening to the trees. How is this done?

Optional Step: Layer Masking

Layer Masking is quite a simple technique and really useful for other areas of Photoshop and not just sharpening. It does require a bit more work though.

If you look down at the right hand lower corner, you should see your background, with “Layer 1” above it (your sharpening layer). Photoshop builds images in layers so you have to imagine that you are looking down at your image (the background layer) through the sharpening layer. What Layer Masking does is “erase” bits of the sharpening layer to allow some parts of your image to be sharp, and others to retain their blur.

  1. On the bottom row, next to the “fx” button, you should see a rectangle with a little hole in it. Hovering over it should give you an “Add Layer Mask” pop up. Make sure your “Layer 1” grey sharpening layer is selected, then click on the rectangle. You should end up with a white box next to your grey layer.
  2. Press “D”, then “X”. This should set your foreground colour to Black and your background colour to white.
  3. Pick a soft edged brush and set the opacity to 50-80%.
  4. Start Painting on your image. Now, wherever you paint black on the mask will “block out” your sharpening. “X” will swap your foreground to white which will “reveal” your sharpening.

If you start getting black paint on your image you’ve probably selected the background by mistake.

This technique allows you to “paint out” sections of the image you don’t want sharp with a very fine degree of detail. So what about when you want to reverse the process? Let’s say you have a portrait where you want the eyes to be really sharp, but not the rest of the face, it’s a very long job to sharpen the image, then spend hours painting everything around the eyes.

In step 1, before you click the “Add Layer Mask” button, hold down the Alt key (Alt+Click). This will create a mask that’s automatically black and you can paint white straight onto the image. This will save a lot of time if you’ve only got eyes to sharpen (for example).

Hope you enjoyed this short tutorial. High Pass Sharpening is a great and simple to use technique.

Ian.

I will get around to writing my article about WordPress – honest! It’s just that this week I’ve been obsessing a bit about my photography. And when I say obsessing, I mean it.

Looking back over time, I’ve bought lenses on a whim, because people said they were the best, because I thought it would improve my photography, and various other reasons. However, when it comes to my next purchase, I want to buy something I need rather than want.  So I began to wonder whether there was a way to look at my images and see what focal lengths I was shooting at. After all, no point in getting a 400mm f4 if I never shoot over 35mm.

After a fair bit of Googling, I found out how to do it. And I discovered that out of the 2,200 images I’ve shot since January, 39% have been with my 50mm/85mm primes, 22% with my 10-20 wide angle, 14% with the 70-200 & 25% with my 24-105. This is interesting in itself, and I find myself wondering whether the 70-200 f2.8L – as the most expensive lens in my bag – would be better off traded against a better lens in the shorter focal length ranges.

Further analysis based on this shows that 85% of my shots are taken at 105mm and below – and with my 10-20mm having just come back from three months away at Sigma, I can only see this rising. Maybe the 16-35 f2.8 would have been a better choice!

I pulled this data from the Lightroom database. Every shot you take and import into Lightroom is catalogued in an SQLite database. That might not mean much to most photographers, and to be honest, it doesn’t need to mean much. But if you get curious, it means you can extract useful information from that database.

All you really need is a working knowledge of Excel (or some similar program) and half a brain. Best of all, it’s free!

Here’s how to go about it.

The Lightroom Database

First up, you really don’t want to mess with your live database. Unless you know what you’re doing I STRONGLY urge you to copy it to a safe location.

Lightroom stores all your photo information in a Catalogue. You can find out where this is by opening Lightroom, and going to Edit>Catalogue Settings>General tab. This will show you the location of your catalogue file – which is really a database.

The Lightroom Catalog Settings window

Open windows explorer and navigate to that location. Right click and COPY your catalogue then paste it to another folder somewhere safe. Don’t drag it, as it may just move the location rather than copy it.

You then need to download a program that can read SQLite databases. I use this one. It’s free. If you don’t want to use this, Google search for “SQLite Browser” or somesuch.

Extract the downloaded zip file to the same safe folder you’ve got your copied database. Within the extracted files, you’ll find an executable (.exe) file. Click this to run the program.

Once it’s open, you can then do File>Open Database and navigate to the COPY of your Lightroom database. Click “Open”

Reading the SQLite Browser for Lightroom

So now you’ve got a window of what appears to be nonsense. And this is what a database looks like. The good news is that the browser makes navigating through the database quite easy.

Every photograph is catalogued with a series of numbers representing various things. Understanding this matrix allows you to extract an awful lot of information about your photographs. Go to the “Browse Data” tab and look at the dropdown menu next to “Table”. Pick AgLibraryCollection. Here you can see some things that begin to make sense.

SQLite view of the Lightroom Library Collection Window

Any image you have tagged with “5 Stars” for example has a local id of 6. So you could query your database to see how many images you’ve 5 starred.

So how does this help?

Well – if you export a table to a .csv (comma separated variable) file, it can be opened in programs such as Excel, where you can then filter, count, analyse and graph your photographic habits.

The tables I’ve found of use are:

AgInternedExifCameraModel

Here you can see the local id assigned to every camera that has taken a photo that is in your database. I have imported stock images from magazine cds, as well as images taken by other people in my Lightroom Catalogue, so there are a lot of shots from different cameras. As you can also see, there are two entries for a Canon 50D in there. One of them is mine, one of them is someone elses. So this is a good place to start looking at your database, as each photograph will be embedded with the local id of the camera. My Canon 50D has a local ID of 1950. (I know this because 2,158 of the images in my database are taken with it)

AgInternedExifLens

This is the lens data. So your own lenses will be on here, as well as any lenses you’ve tried in a shop (as long as the image was imported into Lightroom) and also any lenses used to take stock images from magazine cds. As you can see from this list, a 300-800 lens is in there! It was used to take a stock image of the moon for a photoshop tutorial illustrated in a magazine. By making a note of the local ID of the lens, you can now query the database for that too.

AgHarvestedExifMetadata

So this is what it’s all about (click the thumbnail for a larger image). This lists all your images along with all the EXIF data stored alongside it. This includes things like focal length, shutter speed, lens used, camera body used etc. As you can see, under CameraModelRef and LensRef, only a number is presented. But that number correlates to the local id of the camera and lens in the above two tables. You can see now that by exporting this table to a program like Excel. You can filter against a particular body and/or lens to see which is more popular. You can also graph all the focal lengths to discover which focal length you shoot at most.

You may have noticed that the Aperture and Shutter Speed refer to something other than the actual shutter speed and aperture in a way you understand it. This is because the EXIF data is represented using APEX values rather than real ones. I invite anyone with a stronger grasp of mathematics than I to read the Wikipedia article on this here or have a browse through this pdf by Doug Kerr. If you want to skip all that stuff though, these can be calculated back to real numbers in Excel using the following formulae:

Real Shutter Speed = 1/(2^s) where “s” is the shutter speed given in the EXIF data

Real Aperture = (SQRT(2))^a where “a” is the Aperture value in the EXIF data

Adobe_imageDevelopSettings

This last table is mainly for a bit more fun if you like this kind of thing. It will show you how many images you’ve cropped (in Lightroom). On it’s own, it’s of limited use, but if you tie the local id of the image, to the EXIF data above, you could begin to see how you shoot. For example, if you’re cropping a lot of shots with a 50mm lens, maybe you want to take an 85mm out with you more often. You can even work out the percentage reduction to get a more in depth analysis of your own shooting habits. In this example, rows 743 & 744 have cropped images. You can see the original size as well as the cropped size.

Analysing the Lightroom Database

So all of this is very interesting, but how do you go about analysing it? If you know SQL, the browser program allows you to write a query, but I don’t so I export it to play around with in Excel.

Initially, you need to export the AgHarvestedExifMetadata to a csv file. To do this, in the SQLite Browser program, simply choose File>Export>Table as csv. You then get a pop up asking which table you want to export (chose the Exif metadata one), give it a filename (not forgetting to add the .csv extension!) and save it to a folder. You can then open it in Excel.

Once it’s in Excel, depending on your knowledge of the program there are several things you could do.

– You could simply Find & Replace instances of the CameraModelRef with the real camera name (for example, replace all instances of 1950 with “Canon 50D). Same goes for the lens.

– You could do “CountIf” statements to count how many images (and subsequently what percentage) were shot with a particular lens.

– You could just select the whole “focalLength” column and put it in a chart to see what focal lengths you shoot at. (If you’re anything like me – with a zoom lens, you’ll find the majority of your shots are at either end of the zoom rather than in between)

– You could look at the Date columns to determine when you shoot more photographs.

I am currently working on a macro driven Excel sheet (above) to pull data based on a series of option boxes. It will probably have graphs, charts and a lot of analysis. But that’s just my idea of fun. This may not be for everyone! I can now turn out graphs like this!

 

Mildly exciting!

If you are interested in a copy of the Excel workbook (and macros) when it’s finished, please pop along to the Facebook page and leave a message. If I get enough thumbs, I’ll post it up for download.

Have a good weekend!

-Sc