1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. REMINDER

    Any content, information, or advice found on social media platforms and the wider Internet, including forums such as AP, should NOT be acted upon unless checked against a reliable, authoritative source, and re-checked, particularly where personal health is at stake. Seek professional advice/confirmation before acting on such at all times.

Testing a new lens

Discussion in 'Lens Matters' started by Bazarchie, Aug 7, 2020.

  1. Bazarchie

    Bazarchie Well-Known Member

    Any tips for testing a new (to me) wide angle zoom lens? Cosmetically it is fine and the controls work as expected.
     
  2. Stephen Rundle

    Stephen Rundle In the Stop Bath

    Sounds stupid but just go out and use it all apertures all focus lengths
     
    Learning likes this.
  3. PeteRob

    PeteRob Well-Known Member

    Favourite is to set up square to a brick wall. Then you can see if there is any difference across the frame.
     
  4. Learning

    Learning Ethelred the Ill-Named

    OK if you are doing a U tube review of the thing. Otherwise just do what Stephen suggests.Just use the B thing.
     
  5. Gezza

    Gezza Well-Known Member

    Just keep it on permanently for a while if you can and try using it for anything and everything.
     
  6. GeoffR

    GeoffR Well-Known Member

    Unless you have an optical test bench you only option is to use it! I assume that you don't have an optical test bench, if you did you wouldn't be asking. You have a perfect excuse to go out ant take lots of photographs, as if you needed one.
     
  7. IvorETower

    IvorETower Little Buttercup

    Depends on what you want to test it... its knowledge of chickens, its ability to focus correctly, its ability not to distort...... My usual test of any second-hand lens or camera was to visit Winchester Cathedral and take loads of photos of the inside. However that has been an issue since mid-March :-(
     
  8. Gezza

    Gezza Well-Known Member

    Mine knew very little of chickens..... but it is learning... slowly
     
  9. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    I always set up square to one of the outside natural stone walls of the house when there is a strong oblique light on the rough stone work. This gives good contrast enabling testing of decentering, focus fall-off and light fall-off toward the edges, and chromatic aberration. I test at all full apertures, so I have an idea of what to expect when I use the lens in the field.
     
  10. RogerMac

    RogerMac Well-Known Member

    Google "lens test charts" and you will be offered a choice of free ones ,after that you will need a good printer . Personally I use one that came free with AP some years ago
     
  11. Bazarchie

    Bazarchie Well-Known Member

    Thanks all. I will try the brick wall test to start with as it has been around for years.
    I did print out a lens chart a few years ago and laminated it which was a mistake due to reflections. I have also tried an unlamented version and a newspaper, both of which worked well. Getting the target and the sensor in the same plane is not easy.

    The used lens was described as good, which is two down from the top ranking. I cannot see a mark on it. Whether it is any good optically, I will wait and see.
     
  12. ChrisNewman

    ChrisNewman Well-Known Member

    When I was investigating which digital camera system to choose, I came across horror stories from people who had bought decentred lenses, so I resolved that, with the minimal costs of digital capture, I would test each lens I bought.

    I started by photographing our house wall, but found I struggled to assess whether one brick appeared sharper than another, and I wanted my test shots to show the converging lines on test charts to give me numbers I could compare. I also appreciated that setting up perpendicular to the target was vital, particularly with smaller targets, wider angles and larger apertures. And except for macro, I wanted to know how my lenses would perform with larger subjects than an A4 chart. I decided to base my tests on the central pane of our kitchen window; it’s the largest sheet of glass in our house, it’s almost perfectly flat (although a single pane would be better; sealed units tend to be made concave), and with a dark background and central target on the inner side of the glass, I can use reflection to centre the lens in front of the window. I downloaded a high-resolution PDF copy of an ISO 12233 test chart (drawn by Stephen H. Westin ©Cornell University). I cropped the chart to get the sets of nine black and white converging lines at a suitable scale, reversing two prints to put the converging lines towards the corners of the window. I Blu Tack four charts at the edges of the pane, arranging the height to be 2/3 of the width, align the camera and lens on a tripod using the reflection, and then mount a central chart, focus and shoot.

    I’ve since noticed a test specifically for decentered lenses in a 2012 Lensrentals blog by Roger Cicala, shooting an out-of-focus Siemens Star Chart.

    Good luck with your testing.


    Chris
     
    Bazarchie likes this.
  13. Chester AP

    Chester AP Well-Known Member

    Which lens is it?

    I ask because I've got one of the old-model Sigma 10-20 zooms (purchased secondhand, of course), and after some testing when I first had it, now take 99% of my shots 2 stops from 'fully open' to get the best sharpness over the whole image (this means F 8 at 10 mm and F 11 at 20 mm). At these apertures is is very sharp, and I have a decent 50 x 40 cm portrait format print done from one half of a landscape format shot using a 16 megapixel DSLR.

    Don't expect perfect undistorted images at the wide end of the zoom on the 'brick wall' test unless your camera and lens have some automated correction software in operation (mine does not). Objects towards the corners may look distorted or 'stretched' because they are much further away from the camera than objects towards the centre of the image, due to the large angle of view.

    Also, I've found a circular ND graduated filter so useful that it's been attached to my lens for all my outdoors shots ever since I got it 7 or 8 years ago . You can get a lot of sky in a wide angle shot, and a polarising filter is useless once the angle of view become too wide for it to function as expected, whereas an ND grad does not have his problem. If the horizon 'slopes', just rotate (unscrew) the filter as required.

    Autofocus should work fine on the wall, but outside beware it trying repeatedly to focus on the sky. I use manual focus for most of my outside shots, which is infinity for landscape stuff.
     
  14. Bazarchie

    Bazarchie Well-Known Member

    I did the brick wall test and all seems fine. I will have a go at testing with a test chart and then try to use it when we go on holiday shortly, assuming we are not locked down again.
     

Share This Page