Proper Lens Testing

[DReb-MO]

When you purchase a new lens, what is the proper method to ensure you have a lens that does what it is supposed to do. How do you test a non-IS lens and IS lens? What a bout the IS lens's that have 2 settings? I looked around the forums here by searching lens testing and focus but really didn't find anything. Thanks.

[rdenney]

When you purchase a new lens, what is the proper method to ensure you have a lens that does what it is supposed to do. How do you test a non-IS lens and IS lens? What a bout the IS lens's that have 2 settings? I looked around the forums here by searching lens testing and focus but really didn't find anything. Thanks.

I test lenses by making pictures with them and looking at those pictures on a computer monitor at 100%. I'll find a subject that has nice, sharp detail, and shoot it at a range of apertures. I'll look for the difference between center sharpness and edge sharpness, and for things like color fringing in the corners. Compare to similar lenses only.

I'll also look for things like vignetting with the whole image visible on the screen.

I've been known to take my camera to the store, take pictures with the lens in question in the store, and then go off in the corner analyzing the images at full zoom on the small display.

To test IS, I would choose a shutter speed one or two stops slower than what you think you can hand-hold, and compare images with and without the IS turned on. If both are sharp, go a couple of stops slower on the shutter speed and repeat. Find the speed where the non-IS image shows motion blur, and the point where the IS lens shows motion blur. I'd want two stops at least between them to be worth what IS costs.

Rick "who has no IS lenses but who bought a similar VR Nikkor for his wife" Denney

[DReb-MO]

Thanks. That is very helpful. Do you use some type of target picture? Do you also do the same thing with various focal lengths? I have read about shooting a brick wall but I thought it might be easier to shoot a target indoors under controlled lighting.

[rdenney]

Thanks. That is very helpful. Do you use some type of target picture? Do you also do the same thing with various focal lengths? I have read about shooting a brick wall but I thought it might be easier to shoot a target indoors under controlled lighting.

I don't worry about targets. I just want something that has the sort of detail I like to see in my pictures. Usually, the building out the front door of the camera shop do nicely. I bought my Sigma 12-24 from a camera store in San Antonio, Texas. I had my wife hold the front door of the shop open while I took a few pics of the building across the way. One shop on the other side of the street had signs in their windows, and I blew those up on my LCD panel to compare against another of my lenses at the same focal length. It was enough for me to know that my results greatly exceeded Michael Reichmann's on the Luminous Landscape.

Don't pick anything too close, unless close-focus performance is important for that lens. Non-macro lenses are optimized for 12-feet to infinity, or thereabouts.

If you have a specific requirement, test to that requirement. For example, when I bought the 50mm macro, I tested it by photographing a page in a photo magazine on the rack at the camera store. I was interested in close focus sharpness, and also in flatness of field. So I shot it wide open to see if the focused field was curved, or if the image was distorted (I bought the lens).

Don't forget to check the ergnomics. I rejected the 75-300 lens on ergonomic issues--it was too light to hold steady and there was no way to brace it against anything to limit motion blur. And it was too slow to routinly allow high enough shutter speeds to overcome those problems.

Rick "who thinks you can test cameras as easily by bringing your own memory card to the camera store" Denney

[DReb-MO]

Are there any alternative methods or tips on making sure your new "L" glass is working OK? When I was buying $300-$400 lens's and was less educated I didn't worry about it that much other than to shoot pictures. Now that I have plunged into the realm of "L" I feel compelled to at least make sure everything with my two new lens's are as they should be. Thanks.

[rent]

the one thing i check, aside from just looking down the barrel and visually inspect for dust and other cosmetic defects, is to check focusing.

i set up the camera on a tripod, put a 12" ruler in front of the camera, at the same height. the ruler is placed diagnally so that 1" is closer to the camera and 12" is further.

set the lens to its maximum aperture and auto focus on the 6" mark and take a shot. the resulting image should have the 6" mark sharply focused with even amount of distance in focus in front of and behind the 6" mark.

also, what i usually do with a new lens is to take it in to get cleaned and calibrated by canon before the 1 year warranty runs out. it's kinda convenient for me since the canon service center is just a few blocks away. i think it's still worthwhile even if you have to mail them in.

enjoy your new lens!

-alex

Are there any alternative methods or tips on making sure your new "L" glass is working OK? When I was buying $300-$400 lens's and was less educated I didn't worry about it that much other than to shoot pictures. Now that I have plunged into the realm of "L" I feel compelled to at least make sure everything with my two new lens's are as they should be. Thanks.

[raylks]

The first thing I check when I buy a new lens is to check the dust in the barrel. I must make sure that the barrel is free of dust and clean before I inspect the second crtieria.
Then I will attach the lens on the camera and check the function of AF and MF. Inspect the image through the LCD and see if hot pixel is there.
If you are testing an IS lens, then you shall check the IS function too. It is easy to check. All IS lens in operation will release some noise and when you turn around with the camera, the image on the viewfinder may jump or pop. This is normal for IS lens. If you observe this, you can tell that the IS is working. Then you shoot with slower shutter speed (of course no slower than the limit of the IS specification) to test whether or not you can still get a sharp image.
Then check focus accruacy. I recommend bringing a notebook computer and card reader to the shop. Shoot and check in your computer. Of course sometimes it is not convenient to do so, but you may check it throgh your computer at home.

[DReb-MO]

Thanks for all the information. Now I think I am properly educated and ready to verify that my new lens's are fine and at working at standard specifications.

[Andy_T]

Still,

also take a look at this thread (http://photography-on-the.net/forum/showthread.php?t=58493&highlight=test) if you haven't done so far.

Best regards,
Andy