Appraising Lens Performance........How?

[vanilla]

OK, So i have been at this photographing for a while, but I have this question that keeps bugging me......How to critically appraise lens performance......??

Lots of people talk about pixel peeping, purple fringing, halos, 100% mag etc etc. I have a range of lenses, older and newer, primes/zooms and although I can clearly see some are sharper, and have better colour rendition than others, I would very much like to have some idea as to how you properly appraise lens performance....step by step......I would like to be able to proclaim.....my copy is sharp......

So, who does what...step by step, and what are you looking for ?

 

[rssmrry]

Take a photo, does it look sharp?

Yes - it's sharp
No - it's not sharp

Am I missing something? Why do you need to be able to proclaim that your lens is sharp? If you don't notice it being soft in day to day shooting, why check to see if it's "soft".

(this isn't a go at you as much as it is the whole group of people who feel compelled to check their lenses performance)

 

[vanilla]

OK, I never buy new kit, so it would be nice to take a critical look at any used lenses I buy. Whenever you read about gear in the press, you always hear them talk about the topics I mentioned in the opening post. It would be nice if I could check out my pictures and see how these issues are affecting my exposures.

I figured someone would say 'if it looks good, it is good, so why worry', but it would be nice to have some structured method of looking more closely at an exposure.....after all, we would all still be using kit lenses if we were happy with 'good' photographs right?...the death of 'L' glass !!

 

[AJQS]

My standard test was always to shoot a printed manual from more or less minimumfocus distance. Any piurple fringing showed up as did sharpness and any curvature of field issues.

Then I'd assess other aspects of a lens like flare - wite simple shoot in nasty light, point at the sun - even a briht window in a dark room, does the contrast drop off? does it improve when shaded?

You may alos like to test bokeh qualities - again very easy just throw the focus miles out and see if you like how the out of focus bits look, shape of any specular highlights etc.

It doesn't really matter as ecah lens ahs good and bad bits, just select the appropriate one for the situation.

 

[HoppyUK]

If you just want to see which lens is better than that in some limited but key aspects of performance, side by side under identical conditions, that's quite easy if you know what you're doing. But doing an accurate and thorough comparison, with meaningful numerical measures that can be repeated any time, and referred back to legitimately months or years later, is both complex and difficult.

Lens tests in magazines and on websites take a huge amount of time and skilled effort, and even then most of them are not very good. If you want to make a start, go to www.imatest.com and spend $400 on their basic analysis kit. Anything better than that will cost thousands.

 

[woof woof]

So, who does what...step by step, and what are you looking for ?

I personally don't think that ultimate sharpness is really that important, sharp enough should be good enough and a wise man said quite some time ago that lens sharpness isn't an issue.

I look at the specification, bokeh, level of distortion, vignetting and CA and hope for USM, IS would attract me too but sadly most of the lenses I'm interested in don't have it. Colour and contrast aren't that important to me as I believe that many such things are equalised in post capture processing so unless there's something waaaaaay outside of the norm I'll probably be happy. I'd rather obsess about lens markings than some of the more (to me) irrelevant minor issues.

I've never shot a test chart but when I get new kit I usually shoot an object at every aperture and then take it out for a road test. Once the images are on my pc I'll pixel peep but I'll try to keep in mind that whilst examining images on screen at 100% is something that many of us can't seem to stop ourselves doing it's better to keep in mind what size the final image will be and what it'll look like.

 

[dinners]

Appraising Lens Performance........How?

By all means test it but please just use it - your shots should be the measure.....

 

[vanilla]

Well, here we go then....two pictures, one taken with an economical superzoom, and one with an expensive prime..both at 100mm. Sorry, but I didn't know how to upload a RAW file so they are both in max JPEG (I understand should be looking at RAW file really).

I dial in out EV so pics were roughly exposed to the same level. Its early so I had to use a bit of flash......Its a bit of a rush job but got to work soon....

What do you think ?

 

[ashaz]

no 2 is slightly better imo but there is certainly not much in it.

 

[andyred]

Well, here we go then....two pictures, one taken with an economical superzoom, and one with an expensive prime..both at 100mm. Sorry, but I didn't know how to upload a RAW file so they are both in max JPEG (I understand should be looking at RAW file really) ?

Number 2 looks slightly better on my screen, but there's not much in it.

Can I check it's pulled the exif through properly - both F6.3 @ 1/125 - I presume you hand held. Are these the actual size of shot taken, or have you cropped in.

Don't forget, RAW files will need sharpening.

I've taken the liberty of a very quick edit / sharpen in PSE

 

[vanilla]

Great Andy, thanks.

Yes, they are handheld and no cropping or sharpening was undertaken, I wanted to post them up JPEGS straight from the camera for comparison. The EXIF data you mention is correct.

 

[andyred]

Great Andy, thanks.

Yes, they are handheld and no cropping or sharpening was undertaken, I wanted to post them up JPEGS straight from the camera for comparison. The EXIF data you mention is correct.

No problems

Just done the same very quick edit with the 1st photo...

If you are shooting in jpegs, it's worth checking the cameras settings, are you at maximum / extra fine, is the camera applying any sharpening etc

 

[specialman]

I generally just take a shot under 'regular' conditions (half-decent light, not wide open but stopped down only a little, shutter speed relevant to the focal lenth, low ISO) and if the image looks sharp under close scrutiny, I'm happy. Then I stop worrying and get on with my job.