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PostPosted: Fri Oct 12, 2007 10:43 pm 
I've been wanting to do a comparison test between the D40 with the 18-55 mm (the supplied kit lens) and with the VR 18-200 mm (the nec plus ultra of amateur zooms).

I'm planning to shoot a siemens-star. For this, I have a DIN A3 print (297 x 420 mm or 11.7 x 16.5 in).

However, I don't really know what settings to use, in order to make the results useful. These settings would be the focal lengths, f numbers and distance from the siemens-star.

So, I'd like to ask those of you who are more experienced, for a few hints. Also, if you'd like to add something I've forgotten to ask, please do so. :)

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PostPosted: Sat Oct 13, 2007 7:30 am 
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Joined: Tue Nov 08, 2005 3:32 pm
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Location: Queenstown, New Zealand
Hi Luis, you actually perform the tests at the focal lengths and aperture that you want to measure! I test lenses when fully zoomed-in and out, but you might want to do some middle focal lengths too. As for apertures, try fully open, and then also at f8 which will be close to its sweetspot.

As for distance, it depends on the chart, but for most, you'll want to fill the view with the chart, so the distance depends on the focal length in use.


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PostPosted: Sat Oct 13, 2007 12:12 pm 
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Joined: Sun Nov 05, 2006 11:08 pm
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Location: Germany
Hi Luis,

if you have good lighting or use a flash it's ok to have a flimsy tripod, because the shutter-speeds are fast enough.
If you have an A3 print, just getting it into full view in the view-finder would give approx. 1:25 magnification. All the books say that is too close to judge performance at infinity and too far away to judge close-up-performance.
I'd say: don't worry! Just take a shot with the A3-target filling the frame. Just make sure you're perpendicular (that's what the flimsy tripod is for - or any other support) to the target. At 20mm focal length you should be about 40cm away and at 200mm length you should be around 4m away.

I let the auto-focus do it's work, and it normally does (on a Nikon!). Really critical it is only with apertures below f2.8.

I would be testing wide open, 1 stop down and 2 stops down. Everything else is not critical.

If you want to be absolutely sure about far-away performance repeat at 1:50 (50xfocal length) and just do the centre shot (target at the centre). As the edge/corner-performance has already been tested with the 1:200 shot.

So keep things simple and as long as you get a 8-12mm grey-disk in the centre the shot normally is valid. You can use my resolution measures with the 18-200 as an indicator, as normally the centre-performance is not influenced by decentering, only the borders/corners suffer (differently) from decentering.

If you have any questions feel free.

Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
D810+assorted lenses

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