Sharpen Edges in GIMP

This is a quick note of how to apply image sharpening to the “edges” of an image. One reason for creating this post is so that I have somewhere to find the steps involved when I need them. The steps described are for GIMP. It is likely that you can follow a similar process in other image editing software. It might already be part of how sharpening is done in other application.

Sharpening is usually one of the last things you do to an image before saving it.

With the image loaded into GIMP

  1. Create a duplicate layer.
  2. Apply sharpness to the duplicate layer. Feel free to apply more sharpness that you normally would.
  3. Add a layer Mask to the duplicate but select “Grayscale copy of layer” as you do it.
  4. Right click on the layer mask and select “Show Layer Mask”
  5. Go to “Filters” > Edge-Detect > Edge > OK (I haven’t seen any benefit from making any selections from the Edge dialogue)
  6. While viewing the layer mask go to Colors > Curves and pull “darks” down and “lights” up. i.e. increase the contrast. Part of the idea here is to make areas where you don’t need to apply sharpening black. If you do apply sharpening to some of these areas they can get “pixelly”.
  7. If there are areas you don’t want or need to apply sharpening you can paint those areas black on the layer.
  8. Go to Filters > Blur > Gaussian Blur and apply a small amount of blurring to spread the area that the sharpening will be applied over.
  9. Return to the image i.e. no longer show the layer mask. Right click on the layer mask and un-check “Show Layer Mask”.
  10. Adjust the opacity of the duplicate if required to give you the image you want.
  11. Right click on the duplicate and Merge down to a single image.
  12. Save the file. Go to File > Overwrite…

When I have more time I might add some screenshots of this process.

Concentrating on “Wow!” gives me a blurry Kingfisher?

In a previous post (Roe Deer with Aperture Priority) I talked about setting ISO and aperture to stop the camera insisting on using a high shutter speed with my long lens (a Sigma 150-500mm). Given half a chance my camera (a Canon 7d) will insist on using 1/500s or higher. The resultant large aperture and high ISO then give fuzzy and noisy images. However, when shooting wildlife with a long lens you can only go so slow before you start running into problems.

On Sunday I went to Adel Dam Nature Reserve and had been taking photos of Kingfisher on the branches in the lake. The light was not good but the exposure wasn’t too bad. I had to crop the images and considering the distance I was reasonably happy with the results.


The photo above shows the Kingfisher about to shake the fish and bang it on the branch before swallowing it. This is cropped so I am reasonably pleased with it. 1/180s, f8, 800ISO, 403mm.


But then one of the Kingfisher came close. It perched on a branch to the side of the hide. Unfortunately it was slightly in the shade. I had to be quick to move to the side window of the hide then frame and focus on the Kingfisher and didn’t really look at what the light was doing. Before image stabilisation came along the rule was that you would use a shutter speed that was the inverse of the focal length. So at 500mm on an APS-C camera the rule tells me to use 1/(500 x 1.6) or 1/800s.

Looking at the EXIF data of the image shows that I used f8 and 800 ISO as in the previous image. These settings should give me a good quality of image as long as the subject was still/fixed in the frame. But 1/45s was just too long, and it shows. The branch would have been moving and that kind of shutter speed with a focal length of 500mm means that I was really lucky to get anything recognisable. I think it is good but it should have been better. You should be able to see the individual barbs on some of the feathers on the wings but it is actually quite blurred. I think it is obvious that the cause is camera shake and subject movement.

So what could I have done? What will I try to do next time? The first thing was to look at what settings were being used. Were they the best to use? No? What would be better? How could I get the camera to use a faster shutter speed and do it quickly? With my finger on the shutter release the easiest thing to do would be to dial in some underexposure with the back dial. Shooting in RAW should let me under expose by a stop without losing much colour and detail. In fact, now that I think about it, why didn’t I do that for all the shots I took? Almost as easy would be to use my index finger to dial in a larger aperture before going back to the shutter release. The next thing I could have done was to use my index finger on the ISO button and then on the wheel to dial in a higher ISO.

Frame, focus, take a shot, review settings. Dial in 2/3 stop under exposure. Take a shot. Dial in f6.3, take a shot. Up the ISO to 1600, take a shot. But instead I was looking through the viewfinder at a gloriously coloured Kingfisher and thinking “Wow!” I didn’t want to take my eye off it to review camera settings. If it had stayed on the branch a few more seconds I might have started looking at the camera but it was great to get such a view. It would have been good to get photos at several shutter, aperture and ISO combinations for me to review later. This would all help me to get a better understanding of the settings to use for a given situation. Practice, practice, practice. At the moment I am guessing that I could have tweaked the settings to get a better image.

What it means is that I have to keep reviewing my results after the event and practising so that these things become automatic without them distracting me from enjoying the sight.

Longer term there are a few other things that I could do.

Upgrade my lens to one that gives better image quality at larger apertures. The Canon 400mm f4 prime seems to give good results and is not a daft price.

Or I could upgrade my camera body to the Canon 7d Mk II which gives better quality images at higher ISO.
There are rumours of a Mk III being announced in the first half of 2018.

Roe Deer with Aperture Priority

Unfortunately the big lens I have (Sigma 150-500mm) is not pin-sharp at maximum aperture (But then are any lenses? Well, ones I can actually contemplate owning I mean.) and so when I am cropping an image to get the subject the right size in the frame I am not happy with ones that were shot at maximum aperture.

I have yet to develop the skills where I can adjust ISO, adjust the shutter speed and aperture combination and dial in exposure compensation – all at the same time – while trying to frame the subject and get it in focus. It might sound a bit stupid but there are occasions when I would like to be able to do that. When I have my big lens on my camera (Canon 7d) it will try to keep the shutter speed up between 1/500-1/750 to avoid camera shake and as a result push aperture large and ISO fast. This can (?will) result in images that are noisy and not sharp.

I almost always have a carbon fibre monopod mounted on the lens so I can think about the shutter speed more in relationship to the subject than camera shake. The monopod is one of the legs of my tripod with the centre column on the top.

Roe Deer

This photo was taken with the lens at 500mm and ƒ/8.0, shutter speed was 1/90 and ISO 200.

If the shutter speed had been pushed up to around 1/750 by the camera for this shot then the aperture and ISO would have to compensate 3 stops. Taking it in simple steps my brain can understand to explain where I got the 3 stops – halving 1/90 to 1/180 is 1 stop, halving again to 1/360 is 2 stops then halving again to 1/720 is 3 stops. At 500mm the maximum aperture of my lens is f/6.3 so that would give only 1/2 stop. The other 2 1/2 would have to come from pushing the ISO up to over 1000. (200 > 400 > 800 > 1200 for my simple brain. 1 stop > 2 stops > 2 1/2 stops) Together these would probably result in a borderline image. Given the chance again I would probably have gone for an aperture of f/11.0 and an ISO of 400 to give the same exposure but as is so often the case, you look up and there is the subject. Deer don’t stand around waiting for you to work out the best settings. They see you and then they are off.

Roe Deer

Having spent quite a bit of time with my camera I now know that if the ISO is much higher than 800 I start to get noticeable noise in the images and thar 400 ISO is better. (Should I be going for a Canon 7d Mk II upgrade? But I hear that the low light performance is only 2/3 stop better.) I also know that f/11.0 on my long lens gives sharp results, f/8.0 is still quite good. As a result, on a bright day I will set the maximum ISO to 400 and the aperture to f/11.0. As the light changes during the day I may adjust these settings so that I stand a chance of getting the shot using the monopod.

Of course that is not the end of the story but I will save some of the other considerations for another day.


A Quick Play With HDR

Following some discussion in the camera club I have had a quick look again at HDR, and it is a very quick look. I had used HDR software in the past but I have had several PC incarnations since then and it was no longer installed.

I have just installed Enfuse and used the EnfuseGUI which can create HDR images and, I believe, also do focus stacking. It is open source and so costs nothing. I believe it can also be used as a plugin for Photoshop, Lightroom and Aperture. In that case you use Enfuse and a plugin.

I have put next to no effort into this and I think the results are quite presentable. Because it was so easy I thought I would share it. With a bit of experience who knows what is possible?

The image I have used is a view of the cricket pavilion in Robert’s Park.

Straight from RAW file

The image above is taken from the RAW file. Looking at the settings it looks as though I had very slightly tweaked it – brightened slightly, the contrast increased and the shadows darkened. The sky is a bit (?) nondescript to say the least.

After installing the software I went back to the original RAW file and saved 3 JPEG images from it after changing just the exposure.


With this one I darkened the RAW image several f stops and then saved as a JPEG. The sky looks reasonable but everything else is too dark.

As is

This one is saved as a JPEG from the RAW file with next to no adjustments.


This one is after brightening the RAW file and saving the resultant JPEG. You can now see a bit of detail on the scoreboard.


And the last one is processed through the HDR software accepting the default settings.

I then went through each image and changed the size to 1200×757 and saved at 95% quality. I think the processed one looks quite good. It doesn’t glare at you and was very easy to do. If I was serious about it I should have taken 3 or 5 photos of the scene at different exposures and then worked with loss-less image file formats throughout until the final save as JPEG, but as I said, this was a quick trial and I am quite pleased with the result.

The reason for going back to the RAW file and changing the exposure is that there is much more data in the RAW file. Darkening the RAW file brings detail out of the clouds whereas if I had used a single JPEG the sky might have already been “blown out” – white, with no way of bringing out the contrast between some of the areas as it is darkened. Similarly with the dark areas. Also the JPEG file format looses data and the image can deteriorate every time it is saved.

For an image to render what looks like a wide dynamic range it must darken some areas and lighten others but transition carefully between them. This can cause one of the things I don’t like about some processed images. You can get halos around dark edges. You can often see this along a roof with the sky above.  To maintain the HDR effect the contrast between the roof edge and the sky is kept high in that area but then as you get further into the sky the sky must be darkened to bring out the clouds. This often means that there is a bright halo around the roof. This is one reason why it may be better, in some cases, to do the work by hand.

My camera backpack

When I started off with my Canon 1000D Digital SLR back at Christmas 2009 I bought a small bag that carried the camera, spare battery and lens brush. The following Christmas I got the Canon EF-S 55-250mm lens which still fitted in the bag comfortably.

In 2011 I bought the Sigma 150-500mm lens. For a while I carried this around in the box-like case it came with but this meant that I did not have a way of protecting/carrying it when it was on the camera. I therefore bought a big shoulder bag but I found that this was uncomfortable on long walks even though it had straps to carry it on my back.

I therefore spent a while looking at alternatives and finally bought a Lowepro Flipside 400 AW backpack. I have been very pleased with this but it was a while before I realised that one of the reasons for the waist strap was to allow you to take the straps off your shoulder and swing the bag round to the front, open it and swap lenses etc. without having to take the bag off and put it down somewhere.

I now use it to carry everything other than my second tripod.

The only downside I can think of is that the tripod fits to the front of the bag and the top strap tends to pull it against the bag and squash things up a bit. If the strap is not tight, or if I use only the middle strap then the tripod leans back and spoils the balance when walking. It might be better if the tripod was fitted to the side of the bag so that the weight is closer to your back.

So, either inside this, Lowepro Flipside 400 AW Backpack

or strapped to it, I fit all this –


replaced with a Canon EOS 7D in 2012

Canon 50mm 1.8 lens

Canon 18-55mm lens

with Hoya 58mm UV Filter fitted to protect the lens.

Canon 55-250mm lens

with Hoya 58mm UV Filter fitted to protect the lens.
and Canon ET-60 Lens Hood
Sigma 150-500mm

This filter is not normally fitted due to increased chance of “banding” on out-of-focus lines. Perhaps this is as a result of going for a cheap one. I may post about this sometime. I have noticed it on many wildlife photos on flickr and it is certainly not limited to this lens. The lens hood is deep enough to protect the lens from accidental touching. Maybe I will get the Sigma 86mm filter sometime.

Polaroid Auto Focus Macro Extension Tubes

Giottos Tripod
fitted with Giottos Ball Head

with Ball Head
Spudz Lens Cloth

Extreme Pro 8GB SD Card (read this post about the card)

SD card reader

Lens brush

Air Blower

LCD Display Wireless Remote
(mine is not on Amazon now but this looks like an update to it)

Hoya 58mm Circular Polarizing Filter

Spare battery

Spare battery for the remote release transmitter – bog standard AAA batteries.
Spare battery for the remote release receiver

Olympus voice recorder
– to record sighting and shooting notes. I have yet to use it for that purpose. This is a link to a similar one.

Nikon binoculars

Insect Repellent
– essential when out in the evening along river banks.
Self sealing thick plastic food bag to keep the insect repellant in – I don’t want that leaking over any of the contents of the bag or even leaking on to the bag itself.
A litre bottle of water in a side pocket
Tripod seat This is something I only occasionally take with me.
Collins Bird Guide

I have occasioanlly squeezed my ASUS netbook in there too with a length of network cable and a pair of USB to CAT5 adapters that allow me to connect my camera to the netbook via USB but with the wire between them being readily available network cable. I have yet to use this in anger but it does work.