Depending on the style of work I’m creating I may have a need to sharpen an image. Many iPhoneography apps come with a built in ‘sharpen image’ tool and this may suffice. However, unless the image to be sharpened is reasonably clear and free from noise it is likely that sharpening will degrade the image rather than enhance it. For this reason my preferred method of iPhoneography sharpening is to use the High Pass filter method.

This iPhoneography tutorial will run through the process with screen captures at each stage. The app I use to achieve this is PhotoForge2, although other apps may well have this filter and provide similar functionality

Why is High Pass potentially more effective than standard sharpening?

All devices rely on good light to capture top quality noise free images. Traditional DSLR cameras provide ISO control to adjust how responsive the sensor is to the amount of light reaching it. This means that relatively low light levels can generate a good quality image. Typically though a high ISO setting (meaning the sensor is more responsive to low light conditions) will result in a lower quality image with increased noise. Sharpening images of this nature will often serve to highlight the lower quality by sharpening everything in the image.

iPhoneography provides no control over ISO. Looking at some advanced camera replacement apps such as ‘645 Pro’ it is possible to view the ISO setting the iPhone has selected but it cannot be controlled. Additionally, the hardware involved such as the sensor is nowhere near as advanced as that in a DSLR. Therefore iPhoneography images, are especially susceptible to degradation in low light situations and the point at which light becomes ‘poor’ will be earlier in the day than for a DSLR.

Quite often therefore I may be working with a noisy image. The beauty of the High Pass method is that it finds and focuses on sharpening the edges of objects. These are precisely the items I want to sharpen, leaving noisy areas largely unaffected.

iPhone photography apps used:

iPhoneography High Pass Sharpen

{ iphoneography tutorial ~ using High Pass Filter to Sharpen – PhotoForge2 }



PhotoForge2 ~ open image:

PhotoForge2 - Open Image

PhotoForge2 ~ open layers:

PhotoForge2 - Layers

PhotoForge2 ~ create a duplicate layer:

PhotoForge2 - Duplicate Layer

PhotoForge2 ~ select High Pass filter from FX menu:

PhotoForge2 - Filters (High Pass)

PhotoForge2 ~ aim for a strength around 200:

PhotoForge2 - High Pass (strength 200)

PhotoForge2 ~ select blend method:

PhotoForge2 - Blend Method

PhotoForge2 ~ hit the icon circled to see the blend method applied in preview:

PhotoForge2 - Overlay

PhotoForge2 ~ I usually select Overlay with an opacity of 100% but adjust to taste (Soft Light and Hard Light are also possible options together with reduced opacity levels):

PhotoForge2 - adjust opacity

PhotoForge2 ~ finished:

PhotoForge2 - iPhoneography sharpened

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  1. Andrew Tomlinson says:

    Great tutorial Paul….Does this work the same way as the Adobe method here?

    I presume this method of sharpening using Photoforge is none destructive?

  2. Andrew Tomlinson says:

    Sorry, Paul did not realise this was an old tutorial…Photoforge is not available… Are there other apps that do high pass sharpening that you would recommend?

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