How hard is it to check a secondhand lens?
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Are you talking about buying one from a shop, meeting with seller or buying online?
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* Wear on the lens mount - lenses do wear, it's inevitable and often the wear looks worse than you think, but one that is properly bashed around may have been dropped or suchlike.
* Check the contacts are clean(ish) and are all there or if spring-loaded like on Nikons, that they pop out when pressed.
* General damage such as marks the body don't neccessarily means a poor lens but marked optics can mean big problems, as can chips in the body around the front element. It could have been dropped.
* Look through the lens into the light; dust specks will show, although they don't always means the lens will perform badly (all my lenses have some specks in and work fine). Misting or mould will show up doing this.
* Check the zoom and focu rings move smoothly and don't feel gritty. Also check the rubber on these zoom rings to see if they're firmly in place.
* If the lens is high-end it may have a rubber gromit (wether seal) around the lens mount - check this is intact and not all broken and cracked.
* Check it works on your camera - the usual like stopping down, pressing the DoF preview button, taking a few shots ate different apertures and distances, zooming. Check the AF/MF slider works.
* If it's a Nikon AF-D lens you're looking at, check the aperture ring works AND locks so it can be used.
* Check it has a serial number
* If it comes with a lens hood then it should work (i.e fit on the lens). If not, knock down the price....
* If there's a filter on the front them check it comes off just to see that the thread isn't buggered.
* Check the rear element for scratches.
* Check all the screws are in the lens mount - missing screws could mean someone's been fiddling and that it could have been (badly) repaired.
* Check the contacts are clean(ish) and are all there or if spring-loaded like on Nikons, that they pop out when pressed.
* General damage such as marks the body don't neccessarily means a poor lens but marked optics can mean big problems, as can chips in the body around the front element. It could have been dropped.
* Look through the lens into the light; dust specks will show, although they don't always means the lens will perform badly (all my lenses have some specks in and work fine). Misting or mould will show up doing this.
* Check the zoom and focu rings move smoothly and don't feel gritty. Also check the rubber on these zoom rings to see if they're firmly in place.
* If the lens is high-end it may have a rubber gromit (wether seal) around the lens mount - check this is intact and not all broken and cracked.
* Check it works on your camera - the usual like stopping down, pressing the DoF preview button, taking a few shots ate different apertures and distances, zooming. Check the AF/MF slider works.
* If it's a Nikon AF-D lens you're looking at, check the aperture ring works AND locks so it can be used.
* Check it has a serial number
* If it comes with a lens hood then it should work (i.e fit on the lens). If not, knock down the price....
* If there's a filter on the front them check it comes off just to see that the thread isn't buggered.
* Check the rear element for scratches.
* Check all the screws are in the lens mount - missing screws could mean someone's been fiddling and that it could have been (badly) repaired.
Last edited:
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Cheers guys 
Forgot to add; if the lens has VR/IS then check the system spools up and works.
Forgot to add; if the lens has VR/IS then check the system spools up and works.
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I have just one thing to add to specialman's very useful list.
If a lens has taken a knock, there might not be any external signs, but internally one or more of the optical elements may have become misaligned. There's an easy way to test for this.
Find a high-contrast target like a road sign or a car number plate, in good light. Focus on the target, re-compose so that the target is in the upper right corner of your frame, shoot. Repeat three times with the target in the other three corners of the frame. Examine the pictures on the camera LCD at maximum magnification. You're looking for all four to be equally sharp. You shouldn't worry too much about how sharp they are in absolute terms - most lenses aren't too good in the corners. But you do want the four corners to be the same!
If a lens has taken a knock, there might not be any external signs, but internally one or more of the optical elements may have become misaligned. There's an easy way to test for this.
Find a high-contrast target like a road sign or a car number plate, in good light. Focus on the target, re-compose so that the target is in the upper right corner of your frame, shoot. Repeat three times with the target in the other three corners of the frame. Examine the pictures on the camera LCD at maximum magnification. You're looking for all four to be equally sharp. You shouldn't worry too much about how sharp they are in absolute terms - most lenses aren't too good in the corners. But you do want the four corners to be the same!
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Good point Stewart. We have a 28-135 at work like this.... It's like having built-in schiemflug!!!
KIPAX
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if it has a tripod collar... lossen and make sure it turns smoothly.. even remove (its a 2 second job) and check underneath.. It cost me nearly 300 quid to have a sheered screw replaced by canon under the collar as they had to replace the whole section..
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my 2nd hand 120-300 had a tight spot on the zoom ring where it stiffened up briefly, sent it to sigma and the inner focus mech and cams were distorted (i.e. bent from a hard knock).
might be something else to check for.