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02-04-2014, 10:03 AM   #1
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How to test a lens in a showroom?

Hello everybody,

I'm planning to buy an expensive lens compared to what I have so far, namely Sigma 35mm F1.4 Art. I will go to the showroom and they will probably allow me to test the lens using my body (a Pentax K-5). But... how do you actually test a lens? especially that the K-5 is not that great focusing in low light, and even if they let me go outside the store light is pretty bad at this time of the year. Should I choose a sunny day and go when the light is strong and maybe try to focus outside a window?

Some Canon/Nikon users who bought the same lens reported problems regarding infinity focusing. How do I test this... should I try to AF something very far away ? any suggestions regarding how to test a lens when you buy it are welcomed!

02-04-2014, 10:15 AM   #2
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I usually try AF tests from something close to something far away. My store I frequent is in a mall so I usually try to focus on the store across the way and then on a display right in front. If it locks quickly and easily I'm happy there. I look for play in the focus ring and zoom ring (if applicable), check to see the aperture blades aren't binding. I set it for Aperture priority and ramp through from wide open to closed (usually on the counter with another lens/camera to focus on) and check the screen to see if the depth of field looks correct and that the exposure looks correct (They should all be the same).
02-04-2014, 10:16 AM   #3
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QuoteOriginally posted by Hattifnatt Quote
Hello everybody,

I'm planning to buy an expensive lens compared to what I have so far, namely Sigma 35mm F1.4 Art. I will go to the showroom and they will probably allow me to test the lens using my body (a Pentax K-5). But... how do you actually test a lens? especially that the K-5 is not that great focusing in low light, and even if they let me go outside the store light is pretty bad at this time of the year. Should I choose a sunny day and go when the light is strong and maybe try to focus outside a window?

Some Canon/Nikon users who bought the same lens reported problems regarding infinity focusing. How do I test this... should I try to AF something very far away ? any suggestions regarding how to test a lens when you buy it are welcomed!
Honestly, there isn't much you can do in the showroom, at least not as far as formal tests are concerned. I would just verify that the AF works and that the lens can take a sharp photo, which could ensure that you don't get a dud.

Adam
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02-04-2014, 10:19 AM - 1 Like   #4
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I'm not sure this is a perfect solution but my local store does have a 14 day return policy on purchases. That's one way to test it.

02-04-2014, 10:40 AM   #5
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Proper testing for decentering would require a brick wall and a tripod. Preferrably a shutter release cable too. If you just want to test the af, bring a ruler into the store and take some shots of the mm scale at a45 degree angle from above. Then zoom in and check in camera if the right place is in focus. Switch to manual. Put at infinity. Switch to af. Repeat until you feel confident that the af works
02-04-2014, 12:01 PM   #6
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QuoteOriginally posted by blackcloudbrew Quote
I'm not sure this is a perfect solution but my local store does have a 14 day return policy on purchases. That's one way to test it.
THIS X eleventy billion!!! As Adam says, I would verify that it works and verify the return policy. Then, in that allotted time, I would use the heck out of it in order to test it.
02-04-2014, 12:23 PM   #7
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I think I will opt out for the ruler solution... I will try to brink a white ruler (not a transparent one) and check the results zooming on camera display.

I could also print out some paper for sharpness testing and bring it with me.

I checked the return policy and indeed I can return the item in 10 days without a reason, but it must be "unused". It is specified that for lens one picture is considered "used" )


Thanks for the suggestions guys feel free to bring more if you have ay other ideas.
02-04-2014, 03:56 PM   #8
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I would also do a quick check for decentering - open aperture wide, centre focus on a suitable distant object, lock exposure and shoot, flip into manual focus while not disturbing the focus setting and take four shots with that object in each of the frame corners. Replay, zoom in on the LCD and compare. They should all be equally good (or bad).

02-04-2014, 06:05 PM   #9
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This is the kinda daft image I take in the shop, just to make sure the basics are good and do the rest within the returns period.

https://www.pentaxforums.com/forums/attachments/26-mini-challenges-games-phot...amera-shop.jpg
02-05-2014, 07:38 AM   #10
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Maybe also take a laptop or tablet with the proper connection to use an SD card so that you can pixel peep on a bigger screen.
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