Ways to test a lens?

[weltweit]

I have a lens that fell onto a carpet, quite a soft carpet, but I was concerned I may have damaged it. There was no immediately noticeable damage, it fell on its side so focussing elements and front and rear elements were not impacted.

I tried walking about taking photos with different settings and can't make my mind up about its condition.

My concern is that internal lens elements may have been pushed off centre.

If I gently shake it, it slightly rattles, more than others of my lenses.

I considered trading it in but if it is damaged I wouldn't feel right doing that.

How should I be testing this lens?

 

[editor]

If it's taking good pics and there's no weird grinding it should be fine. I've got one lens that a friend dropped onto concrete and it still works fine, although the front is a bit bent!

 

[weltweit]

If it's taking good pics and there's no weird grinding it should be fine. I've got one lens that a friend dropped onto concrete and it still works fine, although the front is a bit bent!

editor what about the slight rattle when I shake it?

 

[editor]

editor what about the slight rattle when I shake it?

It shouldn't do that but I've had old lenses that do. If it's focusing and the aperture works then I wouldn't worry about it too much. But maybe don;t shake it!

What lens is it?

 

[weltweit]

..
What lens is it?

Nikon 85mm f1.8 AFD

 

[editor]

Nikon 85mm f1.8 AFD

You're OK

The AF 85/1.8 uses rear focusing - the front group of elements is fixed and the rear group moves to focus the lens. The rear group is held in place rather loosely, so that it does not slow down the AF motor, which means they rattle a little when the lens is shaken. Perfectly normal, nothing to worry about.

Nikon 85mm f/1.8D floating element?

What's up with the noisy internals? Makes me wonder how the images are so crisp. :confused:

www.nikoncafe.com

 

[StoneRoad]

That's interesting !

Something I didn't know ...

 

[weltweit]

Great site that, I had never heard of it.

Thanks for your responses editor, I feel better about it now.

 

[StoneRoad]

The only way I could think of to test a lens is to re-take a known image - perhaps a "test card" series ? - and compare them.

 

[weltweit]

The only way I could think of to test a lens is to re-take a known image - perhaps a "test card" series ? - and compare them.

Yes, someone IRL suggested I download and shoot a test card.
At the moment I don't have a functional printer.
No worries though, I am now happy it is ok.

 

[StoneRoad]

Yes, someone IRL suggested I download and shoot a test card.
At the moment I don't have a functional printer.
No worries though, I am now happy it is ok.

I've used a RAL chart (or paint sample "chips") a couple of times when discussing / disputing the colour rendition of screens and printers ... and making sure I've used the same light source.

 

[RoyReed]

Yes, someone IRL suggested I download and shoot a test card.
At the moment I don't have a functional printer.
No worries though, I am now happy it is ok.

You don't really need a test card. Just photograph something flat with lots of detail like a brick wall.

1. Put the camera on a tripod.
2. Turn off image stabilisation.
3. Make sure the camera is placed perpendicular to the wall.
4. Use a remote release (or use the self timer) with mirror locked up if possible.
5. Take three shots, widest and smallest aperture, and half way in between.

Point three is most important. If you can show a grid in your viewfinder, use it.

Look for even sharpness across the width and height of the image at all three apertures.

If the image shows a difference in focus across the width or height, the lens might need collimating.

 

[weltweit]

..
If the image shows a difference in focus across the width or height, the lens might need collimating.

Hi RoyReed, thanks for your reply, what is "collimating"?

 

[RoyReed]

Collimating = optically aligning all of the lens elements on the same optical axis.

 

[weltweit]

Just done the brick wall test, a few times, it was tricky to find a straight brick wall round here and in the end I had to make do with what was available - a bit lumpy .

At first I just shot from the tripod and it was hard to get a tack sharp shot at f1.8. (I realised I was focussing on a brick that was a little depressed from the main surface) Later with MLU and I had tightened the tripod a bit more I got acceptable shots. At f4, f8 & f16 the images were nice and sharp in all areas immediately.

Settings
f1.8 1/320s ISO800 M mode, pattern, spot focus
f4 1/60s ISO800 M mode, pattern
f8 1/15s ISO800 M mode,
f16 1/4s ISO800

Wall at f1.8, levels adjusted & light sharpen, resize to 3000x2000px


Wall at F8

 

[RoyReed]

Just done the brick wall test, a few times... At f4, f8 & f16 the images were nice and sharp in all areas immediately.

Then there's nothing wrong with the lens.

 

[weltweit]

I am being encouraged to focus fine tune my new lens, even though I am happy with its performance.

Now I have a body that can do that but for the last 19 years I didn't have that option and was contented with my focussing ..

 

[FridgeMagnet]

Basically any decent lens made within the last fifty years is way sharper and has way better performance than you will ever need, and that goes triple for ones in the last twenty years. It's even less important now that digital editing is commonplace because you can correct distortions that would have been a huge pain to fix in the darkroom.

I have Leica lenses which are perfect wide open at F2, but I also have Minolta and Panasonic lenses which are perfect wide open and half the price or less.

The concept of lens performance past "does it take decent pictures", except for a few very specialised purposes which you would know about if you did them, is a con. One of the reasons I like shooting film is to make sure I can avoid that because there's only so much you can pixel peep on a 7mp 35mm scan anyway.

 

[weltweit]

We had a presentation from an accomplished wildlife and nature photographer recently. He spent quite a lot of energy testing his lenses and for example recording dof at particular apertures and subject distances etc etc. He made laminated charts for each lens and stuck them on the relevant lens hoods.

During the presentation he evidenced how knowing his available dof for his lenses at different f-stops and distances helped him optimise a shot. I don't think I will go that far but I might check the focus fine tuning at least on my primes, zooms present way more variables.

 

[weltweit]

And I think one of the tests he did was to find out at which fstop max sharpness occurred, on many lenses it seemed about 2 stops in from wide open, so often f5.6.