How do these looks to you - Images from a lens I want

mrbez

mrbez

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Hi Guys,

How do these look to you.

They are images from a Sigma 10-20 that I have been offered.

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It looks okay to me, or are there better copies to be had?
 
I don't have an exif viewer set-up on this pc, but you need to check the edge sharpness when the lens is stopped down, say around f/22. At the usual working range (f/5 to f/11 or so) most copies are sharp enough, the weakness of the lens is assymetric sharpness stopped right down. Mine for example softens up on the left-hand side, but not at an aperture I would use for practical purposes.
 
I wouldn't try to judge the quality of a lens from a small random image.

Ask the seller to send you some full-size images which have details going all the way into the corners and aren't affected by depth-of-field issues.

A simple way to do this is to choose a high-contrast target such as a road sign and take 4 photos of it, each time putting it into a different corner of the frame. (Remember to ensure it's still focussed on the sign properly each time.) Then compare the sharpness of the 4 full-size images of the target.
 
Edge performance at f22?

I dunno why on earth anyone would want to take a shot like these at f22. Everything from a few feet to infinity will be sharp enough at f8 so I can't see any reason to go to f22 as that aperture will probably create more problems than it could solve.
 
woof woof said:
Edge performance at f22?

I dunno why on earth anyone would want to take a shot like these at f22. Everything from a few feet to infinity will be sharp enough at f8 so I can't see any reason to go to f22 as that aperture will probably create more problems than it could solve.
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You wouldn't necessarily want to shoot at f22, but as a test as to if the lens has assymetric sharpness problems it can help show any problems up by exaggerating them. I agree that for actual, real life use, the only reason for stepping down much below f8 would be to get a slow shutter speed if you weren't carrying or didn't like ND filters.

Eventually someone will come up with a digital camera that does slow ISO (like the 25 iso film that I occasionally use, and even pull an extra stop!) as well as see in the dark stuff :shrug:
 
TheBigYin said:
You wouldn't necessarily want to shoot at f22, but as a test as to if the lens has assymetric sharpness problems it can help show any problems up by exaggerating them.
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Really? Wouldn't any such problems be masked by the huge depth of field?

Or is it the fact that at f/22 you'd expect absolutely everything to be sharp (-ish - there's diffraction to worry about!) that makes any defects easier to spot?
 
well - the first example of a 10-20 that I bought had a bit of a "squint to the left" which was more noticeable the more I dialed up the f-stops - second one which i got as a replacement (Jessops, bless em, swapped without quibbling when I showed 'em the shots) was bang on though. Not really going on anything more scientific than that tbh.

edit: Should say that knowing the occasional QC issues that had been mentioned on here and elsewhere, I basically took the lens home, fastened it to the camera and tripod and shot a series of test pictures before I did anything else. I was back in the shop the same afternoon with a couple of prints that showed the problem :shrug:
 
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Hey Guys,

100% crops are not available as the guy has took the lens to work to post for me today if I want it.

Shall I wait until tonight at least and ask for crops or do they actually look okay?

Is it me, or do the edges on them not look too bad at all?
 
The thing is, there's very little actual detail in the edge of frame items for the top half of the base camp photo, and the second one has even less all-round (and isn't actually full frame so could have been a crop from centre frame)

If you're really concerned, get some proper test shots - as suggested by Stewart - he knows a thing or two about lenses :) - and get the raw files, so you know that they're not fiddled with :) Or - get the guy to post it to you, on the proviso that if the tests you do are crepe, you send it back and get a refund :shrug:
 
looks fine to me. even if it isn't THAT sharp it doesn't even matter. you have to pay a lot of money for pro lenses that are truly sharp.
 
sparkoss said:
looks fine to me. even if it isn't THAT sharp it doesn't even matter. you have to pay a lot of money for pro lenses that are truly sharp.
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1) at these sizes it is impossible to judge
2) it doesn't matter if it is for web use. For large prints it couldn't matter more
3) Tokina 11-16mm and 12-24mm are truly sharp and cost roughly the same

Try it in person first. These pics don't tell anything.
 
Hi Guys,

I got a raw file from the guy last night.

Granted that this isn't the best test shot, but given that it was 1/30th and F4, I am assuming hand held too, how does this look to you?

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100% crop from top left, right, and bottom right. Didn't do the bottom left due to hardly any detail.

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I understand that the image looks quite grainy, I am guessing that he used high iso? Can you tell what the ISO was from the CR2?

EDIT - Sorry, ISO was 400.
 
MrCraigBerry said:
I got a raw file from the guy last night.

Granted that this isn't the best test shot...
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Goodness. How much less helpful could a "test shot" actually be?

The lighting is crap. The image is noisy. There's no contrast and no detail. It might be suffering from camera shake. And it's a 3-dimensional subject so there may be DOF issues affecting the corners.

Is he trying to hide something from you? It sure looks that way to me.
 
I tried getting useful RAW files from ebay sellers, when contemplating a couple Sigma lenses. What a waste of time it was! They either didn't respond, or sent useless ones as a result of their complete inability to take even an average snapshot or an attempt to hide flaws. A few sent badly out focus images and claimed they were 'spot on'.

There is only one take away message here. Try it yourself personally.
 
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