March 2012 - Digital Group - Topaz & Lens Testing

Meeting Notes March 2009 to 2018.
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spb
Posts: 146
Joined: Tue Mar 25, 2008 7:04 pm

March 2012 - Digital Group - Topaz & Lens Testing

Post by spb » Sun Mar 04, 2012 1:53 pm

NEWS

How we laughed last month at the Nikon D800's 38MPx sensor… and we thought that the pixel war was over! At first sight the Nokia 808 Pureview is even more worthy of a spot at the comedy club with 41 Mpx in a cameraphone. However on closer inspection it might not be such as daft idea. Firstly the sensor is proportionately larger and secondly the normal resolution of 5Mpx is achieved by averaging 8 pixels into one and thus reducing random noise. The big question is - have they removed more noise than they've added? Time will tell whether this becomes a mainstream technique.

TOPAZ LABS

Several external speakers in the last year have cited Topaz Adjust (TA) as a tool that they use to achieve dramatic images. In particular, gritty portraits of characterful faces seem to benefit from the strong mid-tone contrast hike that TA can achieve.

Topaz Labs offer a suite of 10 plug-in filters for Photoshop/Elements/Lightroom. Each has a similar interface and is commendably easy to get to grips with. Taking Topaz Adjust 5 as an example, the left hand side of the screen has many presets grouped into folders. There is a small preview of each and they can be applied simply by clicking on them. On the right hand side of the screen are the many sliders whose positions achieve the effects. The presets are merely sets of slider positions and having achieved an interesting effect with a preset, the individual sliders can be tweaked to improve the result. Specific settings can be saved as new presets.

To compare before and after views, press the spacebar or click on the image with the mouse. There is also a button at the top to split the screen into before and after panes. A Snap button enables multiple settings to be remembered and compared. When you are happy with one result click OK to apply it and return to Photoshop.

In order to OK and save the results of the filters you will need to enter a registration key. Individual filters are priced between £18 and £50 and the whole bundle is £187. However there are frequent discounts on offer; 10% is readily available and considerably greater discounts are sometimes offered on promotion or at shows. It may be necessary to copy and paste the registration key into each of the 10 filters although some members stated that they didn't have to do this. A trial registration key is available online which offers full functionality for 30 days.

Other filters in the suite are;
BW Effects - creates interesting conversions to monochrome including vintage processes such as cyanotype, albumen, platinum etc
Clean - reduces detail and optionally adds creative curly effects to edges
DeJPEG - removes artifacts from overly compressed images
DeNoise - does what it says on the tin and can also reduce banding
Detail - increases or decreases detail and colour
InFocus - is a very simple but powerful sharpening tool. Interestingly it can also recover detail from slightly blurred images. I have found that this feature alone is capable of adding as much detail as the sharpening sliders on some images that did not appear to be blurred. Given the superior results from this filter and also the High Pass filter technique, I may never use Photoshop's Unsharp Mask again which is too prone to the bad halos that we have seen all-too often.
Lens Effects - can achieve many lens corrections, distortions, blurs and other simulated optical effects.
Re-Mask - is a powerful tool for achieving selections of image areas that are difficult to separate from adjacent image areas by tone or colour.
Simplify - creates painting, drawing and other artistic derivations of the image including a simulation of the much loved and obsolescent Buzz Simplifier.

A new addition to the set is Star Effects which creates a range of starburst effects to image highlights. This is not currently included in the bundle.

Each filter has one or more tutorial videos to explain it's use and features, and these are an excellent and quick way to learn how to get the best from the suite.

LENS TESTING (and why you shouldn't do it)

Scenario: you have read the reviews and purchased an excellent SLR and one or more lenses. You are getting great results and you are happy. Then one day you look at an image taken under unusual conditions and you notice that the corners are not very sharp or there are some nasty magenta and purple edges to high-contrast subjects. Out of curiosity you take some images of trees against bright skies, brick walls and sheets of newspaper specifically to test the lens. You zoom in at 200% and you are doomed. You will never be quite so happy with your equipment ever again. I know - I've just been there.

It started with my Nikon 18-200 go-anywhere do-anything zoom lens for my D200S. The reviews were mixed; some said it was the only lens you would ever need. Others said it was a disaster. It was £500, so I thought that it should be acceptable at the very least. Unfortunately the image corners were a smeary, blurry mess. I took it to Fixation who said that it was 'within specification' so I sold it. If I hadn't looked in the corners I would have been happy.

The D200S was later upgraded to a D7000 and with it came a Nikon 18-105 VR lens. It was a lightweight, plastic mount kit lens and with a value of £230 I felt that it was not quite as sharp as it might be. After reading excellent reviews I purchased a Tamron 28-75 zoom (£280) which didn't have VR but did seem sharper. Having later sold some other equipment, I thought that I would invest in better glass so I purchased a Nikon 16-85 VR (£450) and a Nikon 35mm f1.8 prime (£170). I then set about testing them, as follows;

Corner Sharpness. The first area in which we may notice problems. Finding shortcomings in the corners of every lens I own, I took advice never to worry about it again. The subject is invariably nearer the middle of the frame and we usually crop out the edges anyway. Just don't go there.

Barrel/Pincusion Distortion. All lenses have a degree of distortion, especially zooms and these days the software knows about it and corrects it in camera or in the Raw conversion. Luckily I don't take pictures of brick walls for a living and I resolved not to worry about it.

Front/Back Focus. This is more significant. Having researched many articles on the web I found Jim Jackson's http://focustestchart.com/focus21.pdf excellent article and printed out his test chart. Setting up the chart at 45deg, I put the camera on spot focussing and the lens on maximum aperture. The results from all of my lenses at a range of focal lengths were consistent and worrying. At about 1 metre the images were only sharp about 5% behind the focussing point. At 2.5 metres it was more like 10% behind. The body appeared to be back-focussing. Roger Wotton suggested a further test - manually focussing with the viewfinder and also with the Live View on the camera back screen. Through the viewfinder, the back-focussing error was the same as with AF. However the results with Live View were accurate. This confirmed that the camera was back-focussing and it went back to Fixation for adjustment under warranty. Everything then re-tested OK.

NB There is an AF Fine Tune feature in the D7000 menu. Although it fixed the back-focussing, it then became impossible to focus at infinity at full aperture so it was effectively useless for everyday purposes.

Centre Sharpness. Having fixed the body, this is the key test of a lens - is it sharp in the middle and at what apertures? There are many test charts to download. I used Ian Grey's and shot a series of images on autofocus at a range of apertures and focal lengths. I then processed the sets of Raws for each lens, opened them all in Photoshop and used Window>Arrange>Tile. I viewed one at 100% and centred the image on the chart crosshairs and used Window>Arrange>Match Zoom and Location to do the same to all of the others. A screenshot then gave me a record of the whole set in one frame. See the results here.

So what did I find? The tests showed that no exposures using apertures in the f20's or 30's were sharp because of the diffraction effect. This is to be expected. All lenses were sharp at medium apertures - good. However the revealing results were at the largest apertures for each lens. The cheapo plastic Nikon 18-105 VR kit lens was sharp throughout. The inexpensive Tamron 28-75 has a fixed f2.8 maximum aperture but was not sharp at that aperture at any focal length. The more expensive Nikon 16-85 VR was unsharp at the widest aperture at all focal lengths and even at f8 at 16mm. The Nikon 35mm prime was good but not perfect at f1.8. Finally I tested my Nikon 12-24 which was surprisingly sharp at all apertures.

So my conclusions were that you don't necessarily get what you pay for - expensive lenses can be less sharp than cheaper lenses - and general vague perceptions about the performance of lenses can be wrong . Admittedly these these were not very scientific and I didn't look at aberrations, flare and other factors and cheap lenses will be less robust. Batch variations will mean that no two lenses will be identical. My advice would be that if you are happy with your camera and lenses, don't go looking for trouble!

NEXT MEETING

Thursday 29th March when Chris Palmer will be talking to us about Printing Papers.

Cheers, Steve Brabner

spb
Posts: 146
Joined: Tue Mar 25, 2008 7:04 pm

Re: March 2012 - Digital Group - Topaz & Lens Testing

Post by spb » Tue Mar 06, 2012 1:18 pm

I bought the Topaz bundle at the end of last year and have subsequently upgraded them to the latest versions. When I did so, BW Effects appeared as a new addition to the set but this would not register with my existing code. The Topaz website stated that upgrades are always free so I took the opportunity to speak with a Topaz representative at the Focus show yesterday.

He was not particularly helpful. Although they were offering the new full bundle for £125 (less than I originally paid) he said that I would have to pay individually for the additional BW Effects filter and he could not better the online price of $59. He did concede that I should be able to get 10% discount from various sources.

The products are excellent but I'm a little unhappy about paying over the odds twice.

Cheers, Steve.

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