gsmith051 Loc: Fairfield Glade, TN

Welcome to the forum. You have a lot of good information on this site to help. I purchased lenses from KEH in Atlanta with absolutely no problem. Buying from a good source is half the battle. Good luck to you.

Canisdirus

I usually mix it up.
A few multiplication questions, followed by some English Lit.

rodpark2 Loc: Dallas, Tx

I use my own test target, my front porch decor. I can see highlight-shadow detail, resolution-sharpness, color and saturation, and compare center to corners, etc. It's a real life situation and I can shoot in bright or flat lighting according to time of day. This works great for me. I've found even some expensive lenses soft on one side or the other at times. Wide angle lenses have a disadvantage because the center and the sides are different distances from the lens so are rarely as sharp across the entire image. It's down and dirty so to speak but allows me to find the best aperture of lenses and eliminate really bad ones.

Wanderer2 Loc: Colorado Rocky Mountains

Here's what I do:

Use two paper targets made for lens testing, one flat one and the other a triangular one for front - back focusing.

Three soda cans set on a railing and shot at a 45 degree angle, again for front - back focusing.

A brick or similar wall,being very careful that the camera and wall are perfectly parallel, for any sign of decentering.

All of the above done on a tripod.

Head out to the great outdoors. Shoot a clear blue sky looking for any spots that would be evidence of foreign material, etc. in the lens.

Lots of photos of highly detailed objects with both the new lens and an known excellent lens for comparison.

Hope this is of some help.

willaim Loc: Sunny Southern California

Purchase it from a respected vendor and that they have a return policy. Try the lens out shooting various subjects using different apertures and under various lighting conditions. If you happened to have a test chart then use that. Most venders, like KEH, Adorama, etc will come with warranties.

amfoto1 Loc: San Jose, Calif. USA

Before you ever put a used lens on your camera, inspect inside it carefully with a flash light. Especially look for any fungus, which can appear in several different ways but if you ever had cheese or bread spoil, you have some idea. Fungus can also look like spider webs or tree branches. Unless you are prepared to spend some money on professional repairs and still may end up with a paperweight instead of a usable lens, reject any with internal fungus and don't mount it on your camera because fungus can infect and damage it too.

Don't be surprised if you see some specks of dust inside the lens when you inspect it with a flash light. There's some in virtually all lenses and so long as there's not a lot, it will likely never effect images.

Also look around the edges for any sign of lens element separation. Lenses have groups of elements inside, some of which are glued together. Separation sometimes occurs between those elements. It usually appears as rough, dense, white haziness near the outer edge of the elements. If it's not too deep set into the element, it may not effect images quality right away. But it's likely to increase and cause problems eventually. It is generally not practical to try to repair unless a good, replacement group can be found.

Also try to inspect internal coatings on the optics and the finish on the inside of the lens barrel, as best you can with that flash light. I've seen coatings flaking off lens elements at times and chunks of the anti-reflective matte black materials loose inside lenses.

Do look for haze on internal elements and "cleaning marks" or scratches on the front and rear exterior optical surfaces. Don't worry if you see a tiny bubble or two in lens elements, especially if it's off center. That's not uncommon in ultra high quality glass and doesn't effect images.

If possible, stop the lens down while shining the light through it to see if the aperture diaphragm forms an even hexagon, octagon, etc. (the shape it forms depends upon the number of blades used). An "out of round" aperture may signal a problem of wear or a sticky blade in the aperture. If it's slight, it won't effect image quality much or at all, but may signal future problems.

Many modern lenses don't have an aperture control ring, are electronically controlled and so can't be stopped down while off the camera. In that case, the best you can do is install the lens on the camera (now that you know it's safe... doesn't have any fungus inside) and use the camera's depth of field preview feature to stop the lens down, inspecting the aperture from the front (don't use "B", the long exposure setting which also opens the shutter.... that exposes the image sensor to the bright light of the flash light unnecessarily.... with mirrorless cameras, you might be best to not use a flash light at all).

Operate the lens focus ring, zoom ring and all switches looking for any stiffness, grittiness, excessive looseness or sloppiness.

Now you are finally ready to take some shots! Look for a large, flat, highly detailed "target", like a brick wall or a weathered fence. Best to use a tripod and try to have the camera's sensor as parallel as possible with the target. Focus very carefully, take a shot, download and enlarge it to inspect more closely. In fact, do a series of shots if you can, at different apertures and a few different distances. With a zoom, shoot the same tests at different focal lengths. (It can help to prepare some 3x5 cards with the settings you'll use written on them, then include them in the shot so you have immediate reference to the settings used.)

When you inspect the images, don't be surprised if the center of the image is sharper than the corners. And don't be surprised if the image quality is better stopped down a little from the lens' maximum aperture... Most lenses are at their best at middle apertures.

Look for differences from side to side or corner to corner.... which might indicate a de-centered lens element.

Field test autofocus for speed, repeatability... also be sure to test image stabilization, if it's in-lens type.

Autofocus accuracy can be tested with specialized targets... but anything set at an angle such as a row of batteries or a line of fence boards or whatever, along with a large lens aperture (shallow depth of field) can give you an idea if the lens is focusing reasonably accurately, and repeatably. Don't worry if it needs some minor calibration such as is possible with some DSLRs, so long as your camera has that feature... OTOH, mirrorless cameras typically don't need and can't be calibrated in that way, because in most cases their AF sensors and the image sensor are one in the same.

If there's any filter on the lens, remove that for the above testing.

I always carry a lens cleaning micro fiber cloth too, just in case. A 300mm lens I bought used from a private party had a UV protection filter on it "from new" and the previous owner told me he'd used it very little. Yet I could see haze on the front element and the underside of the filter. I removed the filter and found it just needed a good cleaning. The haze had formed underneath the filter somehow, supposedly in a non-smoking home, stored in a lens case and for much of it's life on a shelf in a closet. Who knows! Maybe the haze was due to other things such as a natural gas forced air furnace. Didn't matter, since it was so easily cleaned off!

It also can be helpful to read detailed reviews of a lens, with sample images, to have some idea what to expect. It also might remind you of some special feature that you should check.

I'd also shoot some high contrast "edges"... such as fine tree branches against a bright sky... focused and slightly out of focus. This will help you see any chromatic aberration.

Bryan Carnathan at the-digital-picture.com does a great job putting lenses through their paces and posts the test results online for everyone to see. Even if he hasn't reviewed a particular lens you're considering (mostly he focuses on Canon gear), his lens testing processes might be helpful to you.

Do I do all the above? Well, yes I do the inspections I mention. But, to be totally honest, NO... I usually don't do all the test shots I described. I'm too impatient and just want to get out and shoot with the new-to-me lens! I really SHOULD do the tests. They'd identify any possible problems, as well as help me quickly become familiar with the lens' capabilities and it's most "ideal" settings.

Have fun shopping!

Bob Werre

I think any testing done is subject to the original design of that lens. Typically, for instance a Nikon 105 is considered a very sharp lens, while other focal lengths (200mm in my case) might not be so great, but that doesn't mean they aren't well cared for. I once bought a used Hassablad 40mm that I knew was in so-so condition as the front element was scratched. What they didn't tell me was 'somebody' had been into the lens and it didn't seem sharp. I then went out and rented that lens and made a comparison between the two. With proof prints in hand my repair guy set the offending elements correctly and it served me well for several years. So comparing apples to apples will let you decide whether to keep or return. A half million years ago, I shot a lot of jewelry with an 8 x 10 camera on Ektachrome. Sharpness was critical. We decided to buy a new 12" Schneider Repro-Claron lens which was designed for closeup work. We tested three versions and picked one that worked best for that use, however, I have no idea if it would do well with landscapes or using extreme camera movements and what F stop was the sharpest.

one_eyed_pete Loc: Colonie NY

Every lens I have was purchased used. A couple from a private individual. one was purchased from Adorama but the rest from EBAY. I purchased my camera from EBAY. I've been 100% happy with all these transactions and saved loads. I always compare prices from all sources, including Mfg. refurbished. A few tips for EBAY shopping because that has greatest potential risk. Only buy from sellers with 95%-100% positive feedback. Only use Paypal. Look for items that have been well cared for. Read everything in the description very carefully. I prefer to only buy items with original box and packaging (it speaks to how item was taken care of). Carefully evaluate photos of the item for signs of wear and damage. Always check function/performance of the item as soon as received, does it work as advertised.

Remember EBAY has a refund policy if something isn't as advertised but it's best if you don't need to resort to using it.

CO

I've been perplexed with that lately. I just bought my first ultrawide lens - the Tamron 10-24mm f/3.5-4.5 Di II VC HLD. It's been very difficult to evaluate the sharpness at very wide settings.

reverand

There are all sorts of ways of testing a lens, including using specialized charts, measuring contrast at different resolutions, and so on. These are what the professionals use, and one can look up their results on line. But for practical purposes, it's not a bad idea to test a lens under the conditions in which it will be used. I bought a 20-70mm zoom and decided to test it against an older 20-120 zoom, and against fixed focal length lenses (24mm and 35mm). I used a tripod to get rid of one variable, i.e., me. Since I do a great deal of landscape photography and seldom use wide apertures, I tested the lenses at f/5.6, f/8, and f/11, and, obviously, at 24mm and 35mm, and then at 50mm and 70mm against the older zoom. I also was shooting a brightly painted mural on the exterior wall of a building, because it gave me a range of colors and textures (the brick, the fire escapes, the window molding, wires), and because I could focus on a distant plane (i.e., not a cluster of trees at different distances). I was probably 40' from the wall. The resulting photographs allowed me to check the center, the edges, and the corners. The only challenge was making sure I could tell the photos apart, which can be easily managed if you go about this in a systematic fashion.

camerapapi Loc: Miami, Fl.

The majority of my lenses were bought used. Photographers who know what they are doing tend to take good care of the lenses they use. Buying from reputable places like Adorama, B&H and MPB just to mention a few gives you peace of mind because those lenses come with a warranty. I avoid Ebay entirely others love Ebay.

When I buy a used lens first thing I do is a good visual inspection to make sure that what the seller promised stands as said. Then I test the lens to all apertures and that usually tells me about the "sweet spot." If a zoom I test it at all focal lengths. I rely on what my eyes see when the files are enlarged to about 50% of their original size. Be aware that many lenses tend to have soft corners at wide apertures but they do exceedingly well in the middle of the aperture range. A small amount of dust inside the optic seldom interferes with the lens performance.

I hope this helps you.

silver Loc: Santa Monica Ca.

If you really want to see how good a lens is , take a sheet of newspaper and tape it to a smooth wall. Then put your camera and the lens on a tripod and get as much of the newspaper page in the frame. Take a picture with good exposure and then open the image on your computer and carefully examine the image from edge to edge. The print on the newspaper will tell you how sharp the lens really is. Carefully look at the edges of the image. Shoot this image at about F8, this should be the sweet spot of the sharpest performance of the lens. This is the easiest and simplest way to judge how good a lens is.

DHoskins Loc: Missoula, MT USA

and I have a bottle of Dawn... thanks!