Focus/Sharpness Expectations

Yes - I believe lighting can matter. I have an 85 1.8 that is so sharp, even wide open, outdoors it hurts yet is consistently soft making indoor dance competition shots. And, of course, use high enough shutter speeds to avoid camera shake, including micro blur.

If you are in lowish light and have NR turned on, this can also soften images as the NR fights the noise at higher ISOs.

armyslowrdr wrote in post #16860527
The link always worked if one took time to log onto his/her google account.

*IF* one HAS a Google account.

MakisM1 wrote in post #16857712
Front/back focusing is not the only reason a lens produces blurry photos.

I always recommend using a target designed for the task AND a proper tesdting process.

You can get a target from this site for free. Print it and glue it on heavy posterboard to avoid distortions/inaccuracy​.

Read their testing procedure and understand/apply it.

Use the procedure only in good natural light.

http://www.peleng8.com …k-focus.html#.U1kSTo_ANa​g

There are lenses out there, no matter how much testing, adjustment you make, will never be critically sharp. This is due to design. Also most lenses aren't at their best wide open, even top shelf offerings from major manufacturers.

Firstly one has to determine if the lens/camera just misfocuses or the lens is optically not sharp.

Gobeatty wrote in post #16860561
Yes - I believe lighting can matter. I have an 85 1.8 that is so sharp, even wide open, outdoors it hurts yet is consistently soft making indoor dance competition shots. And, of course, use high enough shutter speeds to avoid camera shake, including micro blur.

If you are in lowish light and have NR turned on, this can also soften images as the NR fights the noise at higher ISOs.

Low light photography is always a challenge for both equipment and photographer. Images not being sharp in low light when images are sharp in good light is normally the fault of the photographer, unless the camera/lens has difficulty locking onto the subject in low light.

I have a EF 85mm f/1.8 and even in low light this lens focusing is accurate and quick with all my DSLRs.

yogestee wrote in post #16862338
There are lenses out there, no matter how much testing, adjustment you make, will never be critically sharp. This is due to design. Also most lenses aren't at their best wide open, even top shelf offerings from major manufacturers.

Firstly one has to determine if the lens/camera just misfocuses or the lens is optically not sharp.

You think you are saying something different from my post you are quoting?

Apart from generalities, the course you are proposing (whether the lens mis-focuses) is what I proposed, along with the procedure on how to do it.

Incidentally, if one goes through the process, to determine front/back focus, he can get a pretty good idea on how sharp the lens is...

MakisM1 wrote in post #16862780
You think you are saying something different from my post you are quoting?

Apart from generalities, the course you are proposing (whether the lens mis-focuses) is what I proposed, along with the procedure on how to do it.

Incidentally, if one goes through the process, to determine front/back focus, he can get a pretty good idea on how sharp the lens is...

No,, what I'm saying is, a test chart is about as useful as t!ts on a chicken if the lens is optically not sharp. No amount of micro focus adjustment will cure this.

Are you under the impression that shooting a chart with a decentered lens, or otherwise defectively soft lens one will not be able to discern that something is wrong with the lens and one will blithely go on to MFA the lens?

MakisM1 wrote in post #16862826
Are you under the impression that shooting a chart with a decentered lens, or otherwise defectively soft lens one will not be able to discern that something is wrong with the lens and one will blithely go on to MFA the lens?

Images that are constantly soft is also an indication something is amiss. A soft lens may not even be defective. It could just be in the design. There are lenses on the market that are just soft. There are possibly lenses that are soft due to the manufacturing process or just fell through the net during quality control. Nothing you can do about these.

Here's something I'll throw at you. 'Normal' camera lenses aren't designed to photograph two dimensional subjects like test charts, newsprint or even brick walls. Even a carefully set up test with all things being equal will indicate a fall off in resolution from edge to edge, corner to corner,, even with the best lenses. Zooms are worse. Primes are a little better, with macro primes better still. Flat field lenses, which are quite rare are sharp from edge to edge, corner to corner.

I've seen too many lens test gone wrong in these forums by poorly set up procedures which can lead to Imaginitis and open up an entire new can of worms.

If you want to shoot test charts the rest of your photographic life, do so by all means and test using test charts. There's nothing like testing a lens in real world situations. Preferably in low light at full aperture.

I'm saying the opposite. No amount of MFA will cure a poorly designed lens that's just optically soft. Test charts in this situation are totally useless. One has to determine if a lens misfocuses or is just optically soft.

The lens in question is the EF-S 17-55 which is designed to be as sharp as possible.

Adding platitudes and generalities does not make your position right. Most lenses are designed to render a flat surface which is parallel to the sensor as correctly as possible. The fact that lenses are softer as you move away from the center and this softnes can be compounded by a zoom design does not remove anything from the basic premise that the designer is trying to render a flat surface parallel to the sensor in as much fidelity as possible.

The oft repeated bromide

is just that. I don't spend my life testing lenses.

However, if I want to test a lens, I want to do it with a proper methodology, to produce results that are reliable and repeatable.

And by the way, injecting the kind of humor you attempted in this discussion is as useless as teats on a bull!...

Do you tests on a tripod too. I once thought my camera had focus problems or maybe the lens wasn't adjusted to it, but after running through various tests I found my problem was camera shake from hand holding it. Sometimes we just need to use better hand holding techniques and/or a faster shutter speed.

MakisM1 wrote in post #16863074
The lens in question is the EF-S 17-55 which is designed to be as sharp as possible.

Adding platitudes and generalities does not make your position right. Most lenses are designed to render a flat surface which is parallel to the sensor as correctly as possible. The fact that lenses are softer as you move away from the center and this softnes can be compounded by a zoom design does not remove anything from the basic premise that the designer is trying to render a flat surface parallel to the sensor in as much fidelity as possible.

Designed to be as sharp as possible to fit into a market sector.

Excluding flat field lenses, lenses have a curved field and to correct this is complex and expensive. A lens manufacturer is not going to spend millions endeavouring to correct field curvature and then put the lens on the market for a couple of hundred bucks.

Try photographing a piece of two dimensional artwork or even a document, this includes test charts, with any zoom and you'll see where the problem lies.

http://en.wikipedia.or​g/wiki/Petzval_field_c​urvature

http://en.wikipedia.or​g/wiki/File:Field_curv​ature.svg

Tell me,, why do testers, reviewers and manufacturers always give a number MTF readings for their lenses? Centre and edge MTF are always given as separate values. Correct? I've yet to see a 'normal' lens where the centre and edge MTF are identical. I have seen where the edge value is higher than the centre, something possible with macro primes.

Even the legendary Canon 135L the centre is sharper than the edges.

http://www.photozone.d​e …30-canon_135_2_5d?start=1

Yes,, and testing will still show problems with the lens irrespective of how many times you test the lens. What I've seen happen in these forums, especially with new chums to photography or those who aren't aware of lens field curvature, will test their pride and joy only to find the edges aren't as sharp as the centre. Throw in some barrel and/or pin cushion distortion and you have instant can of worms.

In short, nothing beats real world photography when testing lenses.

yogestee wrote in post #16863842
Designed to be as sharp as possible to fit into a market sector.

Excluding flat field lenses, lenses have a curved field and to correct this is complex and expensive. A lens manufacturer is not going to spend millions endeavouring to correct field curvature and then put the lens on the market for a couple of hundred bucks.

Try photographing a piece of two dimensional artwork or even a document, this includes test charts, with any zoom and you'll see where the problem lies.

http://en.wikipedia.or​g/wiki/Petzval_field_c​urvature

http://en.wikipedia.or​g/wiki/File:Field_curv​ature.svg

Tell me,, why do testers, reviewers and manufacturers always give a number MTF readings for their lenses? Centre and edge MTF are always given as separate values. Correct? I've yet to see a 'normal' lens where the centre and edge MTF are identical. I have seen where the edge value is higher than the centre, something possible with macro primes.

Even the legendary Canon 135L the centre is sharper than the edges.

http://www.photozone.d​e …30-canon_135_2_5d?start=1

Yes,, and testing will still show problems with the lens irrespective of how many times you test the lens. What I've seen happen in these forums, especially with new chums to photography or those who aren't aware of lens field curvature, will test their pride and joy only to find the edges aren't as sharp as the centre. Throw in some barrel and/or pin cushion distortion and you have instant can of worms.

In short, nothing beats real world photography when testing lenses.

Hmmm think a controlled test to a chart is what I would base my findingd on. Then by all means try the real world stuff to confirm a fault.

If I think there's something wrong with my equipment, I'm going to test the hell out of it under conditions that, as best as possible, eliminate all of the variables of the real world. That means nerdy lab type treatment.

yogestee wrote in post #16862864
Images that are constantly soft is also an indication something is amiss. A soft lens may not even be defective. It could just be in the design. There are lenses on the market that are just soft. There are possibly lenses that are soft due to the manufacturing process or just fell through the net during quality control. Nothing you can do about these.

Softness is usually one of three things:

1. Missed focus
2. Defect in workmanship
3. Optical design

Charts help you at least confirm or rule out #1. Confirming #1 also confirms #2 because no one designs a lens to focus somewhere other than intended or be decentered on purpose. That means you can decide whether to exchange it for another if possible, send it off to be fixed, or ditch that particular copy entirely.

If you rule out #1 then you bump to #3 and can decide whether you can live with that lens' optical qualities. If not, you can decide whether to return it if possible or sell it, trade it, or whatever to get rid of it and buy something else entirely. At least you'll know that you have to look at something else rather than try to find a better copy of the same lens.

In other words, I want to find out whether it's me, my particular lens, or the nerd who designed the thing in AutoCAD at fault.

The raw files would be better for review. Not only would they be bigger and more detailed, but DPP could show what focus points were selected.