My 70-200, Opinions Please

[Mr_T]

Hello people of TP

Once again I call upon your vast knowledge of everything photographic to get some opinions. I've had my 70-200 AF-S (Version 1) for some months now and I've been pretty pleased with how it's performed especially wide open. Unfortunately with it being a second hand lens I have always had that niggling feeling that it wasn't as good as it should be (then again this lens does have a lot of hype).

The above coupled with an unfortunate accident with the lens falling off the top of my PC on to the floor has gotten me even more paranoid. I thought I would supply a full size test shot for you all to look at. I've done test charts in the past and I've never found them to be particularly useful so I tried to do a somewhat more realistic test (using a rather old towel).

Exif Data: 1/800th at f/2.8 ISO 400

Full Sized Image: cliky

Does this look about right or should I look into getting it repaired of recalibrated? I'm also not entirely sure about the best place to send it (if there is a problem of course), I've used both Fixation and Nikon before. It may also be worth saying that the body itself has been serviced recently so we can perhaps take that out of the equation.

 

[HoppyUK]

You should not use a flat target at close distance. That is more a test of field flatness than anything else, which all lenses suffer from to an extent, although wide angles are much more prone.

If you want to see if anything has been knocked out of true, or if the lens was poorly assembled (ie 'bad copy') shoot a distant target to minimise focusing errors and eliminate field curvature issues - something at the end of the street like a car number plate or road sign.

Shoot at lowest f/number to minimise depth of field which might otherwise conceal problems. Highest shutter speed you can get to reduce camera shake, and increase ISO if you need to in order to get that. Focus carefully and set exposure, then lock everything in manual so it can't change.

Shoot four pictures with the target in each corner of the frame. Do it quickly as if the light changes, eg sun goes behind a cloud, it will ruin the comparison. Compare the four images of the target at max magnification. If your camera has a decently big LCD, you can do it one screen. The whole operation takes no more than a few seconds - job done.

All four images should be equally sharp, or possibly equally unsharp - this is quite a tough test. You are not looking for perfection, just equality. Since the lens has taken a bash, repeat the test at 70mm, 135mm, and 200mm. Again, you are looking for equality of the four images at each setting, not for the lens to be the same at all focal lengths as it probably won't be.

If any of the lens elements are out of true, one or more corners will be significantly worse than the others. If you're not certain and have to keep checking and double checking, there is probably nothing wrong, or nothing that is not within acceptable tolerance - misalignment errors are usually quite obvious.

Let us know how you get on

 

[StewartR]

I'll second HoppyUK's suggestion. That's a great, quick way to test whether anything in your lens is misaligned.

 

[ditchdigger]

i think for your peace of mind send it back to nikon

my household ins covered me when i dropped a lens some years ago

 

[Tobers]

That has to be one of the most boring images ever seen

However, it does look like your lens is a bit wrong. I had a similar issue with my Canon 70-200 2.8 where the centre was sharp but it became progressively less sharp and very blurry as you moved towards the edges. Not a bit blurry, a lot blurry. Like the left side of your image.

ine was diagnosed by Canon as having a faulty first element set which they replaced and it is now absolutely fab.

Not sure what caused the problem with mine as I hadn't dropped it or bashed it, but it could have been anything as it leads a fairly hard life.

 

[HoppyUK]

I'll second HoppyUK's suggestion. That's a great, quick way to test whether anything in your lens is misaligned.

Cheers Stewart It's such a quick and easy test, and no faulty lens will ever pass it. Handy for when dodgy customers return your hire lenses I guess.

In fact, testing at different focal lengths really shouldn't be necessary unless there is obviously something mechanically wrong, after a drop maybe. In which case, you would almost certainly be able to feel if anything was wrong by turning the zoom and focus rings.

However, to be sure on that score, just repeat the test at max, middle and min zoom, and then do the same again at a closer distance if you think that focusing may be damaged. Be careful with that one though, as depth of field is likely to be very shallow which could throw everything out, plus the previously mentioned field curvature issues. But if you keep the minimum distance over 50x focal length, and are very careful not to move the camera backwards or forwards between frames, eg on a tripod, it should be a valid test.