How should I test a lens?

[Austerby]

I've just bought a secondhand lens from a dealer. It's an old lens and I noticed some imperfections in my examination of the lens which look like pretty normal wear and tear, but they are there. The dealer has allowed me a one month trial, during which I can return the lens for a full refund if I am not satisfied.

What tests should I carry out to see if I should keep the lens or return it for the refund?

In particular, I'm interested if there are any special techniques or subjects I should consider rather than just normal photographic subjects. For example, should I be using wider or narrower apertures; faster or slower shutter speeds; brick walls or trees etc.

(for those who may be curious, it's a 50mm Distagon for a Hasselblad - the C T* model for which I've paid £250, which seems to be at par with internet auction site values. I think the shutter is OK, it's more the optics I'm interested in testing).

 

[Al Kaplan]

Shoot some ix at various distances and different apertures. Make notes. See how you like the shots. Make a few with a bright light in the picure. Does that cause too much flare?

In all probability the lens is just fine. You should check for smoothnes in focusing and check the shutter speeds by changing them together with the aperture. The density of the negatives should all be fairly close.

 

[Roger Hicks]

Shoot a bracketed series of shots of twigs or telephone wires against the sky, over- and under-exposing. This will give you a good idea of flare and real-world sharpness.

Tashi delek,

R.

 

[Chris101]

Don't test it, just shoot with it. If after a month you are not satisfied with what it does, take it back!

 

[Roger Hicks]

Don't test it, just shoot with it. If after a month you are not satisfied with what it does, take it back!

Dear Chris,

Absolutely right in one sense -- but in another, it's worth trying to re-create the (adverse) conditions in difficult shots that might not come up in that month.

Tashi delek,

Roger

 

[FrankS]

Send it to Raid. 😉

 

[ferider]

1st make sure it works mechanically. Aperture and shutter are the most likely things to fail or be of specs. Visual or by ear inspection is enough.

Then take a test roll that shows you performance across the field (center and corner - eliminate possible lens de-centering) at infinity and close-up. For infinity, some land/city-scape with twigs or antennas, for instance. For close up, something with written text is useful. Like several bottles of your favorite wine/beer 🙂

You don't need to test all apertures, wide open and maybe a stop down will show you that the aperture works.

Then like Chris said, forget testing, use it for a while 🙂

I have the same lens and love it. A classic.

Cheers,

Roland.

 

[Austerby]

Next question is how do I critically assess the results? What tell-tales should I be looking for. I don't have access to another sample of the same lens so cannot carry out a comparative assessment - would it be worth comparing to my 80mm Planar? Presumably there's little point in comparing to 35mm lenses?

 

[Al Kaplan]

It will probaably have a bit more flare than your 80 and the corner detail won't be as crisp. Even the old chrome single coated lenses can give you great results. Some people prefer them to the more modern T* lenses. Go run a few rolls through the camera shooting the kind of pictures you'd normally take. Do you like the results? That's the ONLY thing that really matters.

(Then go back to the dealer lens in hand, tell him that it's a nice lens but not all that you'd hoped for, and would he knock another 25 off of the price.)

 

[hans voralberg]

Well if you're happy with the result then it's fine ? If it flares like kingdom come or looks really fuzzy then it's bad, but otherwise I don't see a point for cherry-picking for the best .

 

[vbarniev]

Shoot a couple of rolls. Use a hood.

 

[Austerby]

Something like this? It's into the sun so there is lots of flare but I'm not sure its terminal - what's in focus is definitely sharp and there's good distinction and contrast in a purposefully testing shot. I'm pleased with the rendering of the background too.

Now, to find a lens hood....

 

[Melvin]

To test a lens I eliminate as many variables as possible:
Use a tripod. Camera shake softens images.
Use very fine grain, sharp film. Grainy black and white film softens images.
Take shots at all apertures using the same lighting and metering, of the same subject focused on the same spot.
Write down the aperture and shutter speed for each frame.
What you choose as a subject obviously is determined by what you want to know. Photographing a brick wall might tell you about distortion and resolution, but might not about bokeh or flare, or focusing accuracy, e.g..