Why are images get soft at wide aperture ?

[semi pro photographer]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

But when using f/3.5 ~ f/11 the images are sharper and less blurred .

Even with 50mm f/1.4 and 85mm f/1.8 , when using wider aperture , the images become less sharper .

How can I get sharper images at wider aperture ?

 

[Gerry Winterbourne]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

All simple lenses (that is, just one element) suffer from aberrations of many kinds. See, for example, the bottom half of this link https://en.wikipedia.org/wiki/Lens_(optics) Camera lenses use a number of elements of different shapes (compound lenses) whose aberrations cancel out.

However, it's not possible to get them to cancel out completely so there are always some residual aberrations. As you see from the diagrams in the link, aberrations are caused by the curvature of the glass and that is steeper away from the axis of the lens.

The wider the aperture the more of the outer - steeper - part of the glass is used so the greater the effect of aberrations.

But when using f/3.5 ~ f/11 the images are sharper and less blurred .

All lenses also suffer diffraction - that is an effect of the edges of an aperture on waves (water waves etc also suffer diffraction). The effect of diffraction is tiny at wide apertures and increases as the aperture gets smaller.

The result is that the resolution of a kens is the balance of these two effects. At wide apertures aberrations cause aberrations that soften the image; on first stopping down the effect of aberrations is less and diffraction is still minor so the image gets sharper; then on stopping down further the effect of diffraction gets steadily worse and the image gets softer again.

Even with 50mm f/1.4 and 85mm f/1.8 , when using wider aperture , the images become less sharp.

This is true of almost all lenses. There is always a battle between aberrations and resolution. The more effort and expense the designer makes the less the effect of aberrations but they are always still there. A very few lenses are sharpest wide open but even they suffer some diffraction softening.

How can I get sharper images at wider aperture ?

You can't get any better resolution - it's the nature of lens optics. Sharpness is a combination of resolution and local contrast - you can improve that at any aperture by various digital manipulations.

 

[Guy Parsons]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

But when using f/3.5 ~ f/11 the images are sharper and less blurred .

Even with 50mm f/1.4 and 85mm f/1.8 , when using wider aperture , the images become less sharper .

How can I get sharper images at wider aperture ?

Quality varies from lens type to lens type and maybe is connected to cost of lens at times.

Two things are happening - at wide apertures the depth of field is very shallow, also at wide open apertures the lens often is at its worst - but again that varies. You need to examine the image to see if it is indeed depth of field issues or lens quality issues.

A full resolution sample displayed here may help others make comments.

Have a look at random lens tests at http://www.imaging-resource.com/lenses/reviews/ and use the interactive graphs to see how performance varies with aperture, the lower and flatter the graph the better.

If indeed it is lens faults that cause the softness then only a higher quality and more costly lens may do better.

Oh yes, remove any filters on the front of the lens as you need to test the lens itself and not any additional glass on the front.

Regards......... Guy

 

[MediaArchivist]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

Most wide aperture prime lenses are sharpest around f/4 - f/8 (of course this varies widely). With a wider aperture (like f/1.8) many more aberrations are harder to correct. In addition to these aberrations being more pronounced on the edges and corners, many lenses do not have flat focal planes. Depending on your scene, the edges might be out of focus even when the center is. Exacerbating that is the very shallow depth of field at large apertures. A shallow DoF will also make AF accuracy more noticeable. Since most people accept slightly softer images at wider apertures, as well as a non-flat focal plane, this is usually not considered a problem.

But when using f/3.5 ~ f/11 the images are sharper and less blurred .

Fun fact— if go too much past f/8, the image will be less sharp as diffraction sets in. There's no free lunch.

Even with 50mm f/1.4 and 85mm f/1.8 , when using wider aperture , the images become less sharper .

Some lenses are extremely sharp at the center when used at f/1.4. Some are even sharp in the corners, if you focus properly (the rest of the image might be blurry if you focus on the corner). Other lenses are not

How can I get sharper images at wider aperture ?

1. Get better lenses.
2. Make sure you understand shallow DoF. It can take some practice.
3. Try controlled tests to make sure your AF is accurate.

 

[Brisn5757]

Buy some better quality lens.

Brian

 

[Gerry Winterbourne]

Buy some better quality lens.

Which lenses would you suggest? How much improvement will they give, and at what cost?

 

[golfhov]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

All simple lenses (that is, just one element) suffer from aberrations of many kinds. See, for example, the bottom half of this link https://en.wikipedia.org/wiki/Lens_(optics) Camera lenses use a number of elements of different shapes (compound lenses) whose aberrations cancel out.

However, it's not possible to get them to cancel out completely so there are always some residual aberrations. As you see from the diagrams in the link, aberrations are caused by the curvature of the glass and that is steeper away from the axis of the lens.

The wider the aperture the more of the outer - steeper - part of the glass is used so the greater the effect of aberrations.

But when using f/3.5 ~ f/11 the images are sharper and less blurred .

All lenses also suffer diffraction - that is an effect of the edges of an aperture on waves (water waves etc also suffer diffraction). The effect of diffraction is tiny at wide apertures and increases as the aperture gets smaller.

The result is that the resolution of a kens is the balance of these two effects. At wide apertures aberrations cause aberrations that soften the image; on first stopping down the effect of aberrations is less and diffraction is still minor so the image gets sharper; then on stopping down further the effect of diffraction gets steadily worse and the image gets softer again.

Even with 50mm f/1.4 and 85mm f/1.8 , when using wider aperture , the images become less sharp.

This is true of almost all lenses. There is always a battle between aberrations and resolution. The more effort and expense the designer makes the less the effect of aberrations but they are always still there. A very few lenses are sharpest wide open but even they suffer some diffraction softening.

How can I get sharper images at wider aperture ?

You can't get any better resolution - it's the nature of lens optics.

With those lenses. There are more advanced designs that are better wide open. I am assuming the Canon eF?

The sigma art 50 and 85 look a lot better wide open. You will pay for the luxury

Sharpness is a combination of resolution and local contrast - you can improve that at any aperture by various digital manipulations.

To a degree. A lot less expensive

--
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Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006
http://www.pbase.com/gerrywinterbourne
[email protected]

 

[Gerry Winterbourne]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

All simple lenses (that is, just one element) suffer from aberrations of many kinds. See, for example, the bottom half of this link https://en.wikipedia.org/wiki/Lens_(optics) Camera lenses use a number of elements of different shapes (compound lenses) whose aberrations cancel out.

However, it's not possible to get them to cancel out completely so there are always some residual aberrations. As you see from the diagrams in the link, aberrations are caused by the curvature of the glass and that is steeper away from the axis of the lens.

The wider the aperture the more of the outer - steeper - part of the glass is used so the greater the effect of aberrations.

But when using f/3.5 ~ f/11 the images are sharper and less blurred .

All lenses also suffer diffraction - that is an effect of the edges of an aperture on waves (water waves etc also suffer diffraction). The effect of diffraction is tiny at wide apertures and increases as the aperture gets smaller.

The result is that the resolution of a kens is the balance of these two effects. At wide apertures aberrations cause aberrations that soften the image; on first stopping down the effect of aberrations is less and diffraction is still minor so the image gets sharper; then on stopping down further the effect of diffraction gets steadily worse and the image gets softer again.

Even with 50mm f/1.4 and 85mm f/1.8 , when using wider aperture , the images become less sharp.

This is true of almost all lenses. There is always a battle between aberrations and resolution. The more effort and expense the designer makes the less the effect of aberrations but they are always still there. A very few lenses are sharpest wide open but even they suffer some diffraction softening.

How can I get sharper images at wider aperture ?

You can't get any better resolution - it's the nature of lens optics.

With those lenses. There are more advanced designs that are better wide open. I am assuming the Canon eF?

The sigma art 50 and 85 look a lot better wide open. You will pay for the luxury

These are screen shots of the Sigma 85/1.4 Art and Canon EF85/1.8 from the Photozone reviews. Both follow the pattern I described. The Nikkor 85s (1.4, 1.8) follow the same pattern. PZ hasn't reviewed the Sigma 50/1.4 Art so I can't show that but its ordinary 50/1.4 starts very soft wide open.

Note that PZ shows resolution on bands that relate to the pixel density of the camera used to test so the numbers aren't comparable but the shape (towards the top of "very good") is.

The Nikkor 85s are equal to each other at f/1.8; the Sigma 85/1.4 Art is about 6=7% sharper. That's not what I'd call "a lot better" - it's often said that the "just noticeable difference" for resolution is 10-15%.



--
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Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006

Galleries by Gerry Winterbourne

www.pbase.com

[email protected]

 

[golfhov]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

All simple lenses (that is, just one element) suffer from aberrations of many kinds. See, for example, the bottom half of this link https://en.wikipedia.org/wiki/Lens_(optics) Camera lenses use a number of elements of different shapes (compound lenses) whose aberrations cancel out.

However, it's not possible to get them to cancel out completely so there are always some residual aberrations. As you see from the diagrams in the link, aberrations are caused by the curvature of the glass and that is steeper away from the axis of the lens.

The wider the aperture the more of the outer - steeper - part of the glass is used so the greater the effect of aberrations.

But when using f/3.5 ~ f/11 the images are sharper and less blurred .

All lenses also suffer diffraction - that is an effect of the edges of an aperture on waves (water waves etc also suffer diffraction). The effect of diffraction is tiny at wide apertures and increases as the aperture gets smaller.

The result is that the resolution of a kens is the balance of these two effects. At wide apertures aberrations cause aberrations that soften the image; on first stopping down the effect of aberrations is less and diffraction is still minor so the image gets sharper; then on stopping down further the effect of diffraction gets steadily worse and the image gets softer again.

Even with 50mm f/1.4 and 85mm f/1.8 , when using wider aperture , the images become less sharp.

This is true of almost all lenses. There is always a battle between aberrations and resolution. The more effort and expense the designer makes the less the effect of aberrations but they are always still there. A very few lenses are sharpest wide open but even they suffer some diffraction softening.

How can I get sharper images at wider aperture ?

You can't get any better resolution - it's the nature of lens optics.

With those lenses. There are more advanced designs that are better wide open. I am assuming the Canon eF?

The sigma art 50 and 85 look a lot better wide open. You will pay for the luxury

These are screen shots of the Sigma 85/1.4 Art and Canon EF85/1.8 from the Photozone reviews. Both follow the pattern I described.

I am confused by something. Using the data you provided the Canon 85 never even matches the wide open resolution of the art. Regardless of stopping down. Are these tested with the same bodies?

The Nikkor 85s (1.4, 1.8) follow the same pattern. PZ hasn't reviewed the Sigma 50/1.4 Art so I can't show that but its ordinary 50/1.4 starts very soft wide open.

yes. The older sigma is an entirely different discussion. As are those nikkors that I did not mention

Note that PZ shows resolution on bands that relate to the pixel density of the camera used to test so the numbers aren't comparable but the shape (towards the top of "very good") is.

so different bodies?

Do you misunderstand me? I was not stating that many other lenses are at there very optical best wide open.

"There are more advanced designs that are better wide open."

well I can see how I am confusing. Perhaps I should have said "give you better results wide open"

The Nikkor 85s are equal to each other at f/1.8; the Sigma 85/1.4 Art is about 6=7% sharper. That's not what I'd call "a lot better" - it's often said that the "just noticeable difference" for resolution is 10-15%.

I didn't mention the nikkors. I also don't know if it is entirely fair to compare 1.4 and 1.8 lenses at their different wide open apertures equally.

Any other sites?

--
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Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006
http://www.pbase.com/gerrywinterbourne
[email protected]

I know everyone hates this one

DXOMARK

www.dxomark.com

If I have made a mistake please correct me. Perhaps "much better" was a harsh term. I will take "better".

 

[sybersitizen]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

That's absolutely normal behavior with lenses that were designed for general use and reasonable budgets.

How can I get sharper images at wider aperture ?

You can't change the behavior of the lenses you already own ... but you can buy very expensive lenses that were designed and manufactured to have much better performance at wide apertures. Your choice.

BTW ... how long have you been a semi pro photographer?

 

[Brisn5757]

Buy some better quality lens.

Which lenses would you suggest? How much improvement will they give, and at what cost?

--
---
Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006
http://www.pbase.com/gerrywinterbourne
[email protected]

It depends on the photographers needs. All I'm saying that all lens have limits and to get better quality you sometimes need to upgrade the lens.
There are some good guides and reviews of lens on this site.

Brian

 

[BAK]

Imagine a camera on a tripod, pointed flat at the door in the middle of the side of a barn. Get a long piece of string, tie it to the lens, and walk to the door. Tie a knot in the string.

Now walk the the left end of the barn. (or the right. Your choice) The string doesn't reach.

So, how far is it from the camera to the barn?

That may be 40 feet to the middle, and 50 feet to the edge.

Some lenses, call flat-field lenses, are designed to keep the whole side of the barn sharp.

Most macro lenses, optimized for copying flat documents, are flat field. So the edges, wide open, are almost as sharp as the center.

Go to Photozone.de and look up the Canon EF-S 60mm lens.

Wide open, edge and center, not much difference.

Take a look at the Canon EF 50mm f1.4

Huge difference wide open between edge and centre.

Not corrected very well for flat field.

But see what happens as the lens is stopped down and depth of field increases, "pulling" the edge sharpness up the scale.

EXPERIMENT

Put your camera on a tripod and set a couple of cereal boxes up on a table.

Position the camera so it sees the full faces of the boxes, and probably some tabl and some of the back wall.

Open the lens to maximum aperture, take a picture, and look at it carefully.

The edges are probably soft.

Now put a couple of tall, slender, boxes up a few inches in front of the edges / sides of your wall of boxes.

Take a few pictures with the side boxes closer to and farther from the wall of boxes.

POOR LENS DESCRIPTIONS - the lens companies do a bad job telling us about flatness of field, and modern lenses are flatter than older ones, more or less and most but not all of the time.

MODERN GLASS and COMPUTER AIDED DESIGN makes lenses better.

BAK

 

[FingerPainter]

A very few lenses are sharpest wide open but even they suffer some diffraction softening.

How can I get sharper images at wider aperture ?

You can't get any better resolution - it's the nature of lens optics.

With those lenses. There are more advanced designs that are better wide open. I am assuming the Canon eF?

The sigma art 50 and 85 look a lot better wide open. You will pay for the luxury

These are screen shots of the Sigma 85/1.4 Art and Canon EF85/1.8 from the Photozone reviews. Both follow the pattern I described.

...

Do you misunderstand me? I was not stating that many other lenses are at there very optical best wide open.

"There are more advanced designs that are better wide open."

well I can see how I am confusing. Perhaps I should have said "give you better results wide open"

I presume that Gerry meant that lenses are better stopped down a bit then the same lens wide open, while you meant that some lenses are better wide open than other lenses are wide open, but you have been misinterpreted to mean that some lenses are better wide open than the same lens stopped down a bit.

I know everyone hates this one

I don't hate it. . The data at the following link show that the Sigma 50mm Art is much sharper stopped down to f/1.8 than it is wide open at f/1.4, and even sharper at f/2, f/2.8 and f/4. This is the effect that Gerry described. The data also show that the Sigma 50mm Art wide open at f/1.4 is sharper than the Canikon 50mm f/1.4 lenses are wide open at f/1.4. So you are both right.

https://www.dxomark.com/lenses/bran...dOptions=false&viewMode=list&yDataType=global

If I have made a mistake please correct me. Perhaps "much better" was a harsh term. I will take "better".

I think the confusion lies in what is being compared to what.

 

[Gerry Winterbourne]

With those lenses. There are more advanced designs that are better wide open. I am assuming the Canon eF?

The sigma art 50 and 85 look a lot better wide open. You will pay for the luxury

These are screen shots of the Sigma 85/1.4 Art and Canon EF85/1.8 from the Photozone reviews. Both follow the pattern I described.

I am confused by something. Using the data you provided the Canon 85 never even matches the wide open resolution of the art. Regardless of stopping down. Are these tested with the same bodies?

Read the paragraph below that I've made bold. PZ has used different cameras over the years so the numbers quoted can't be compared directly. However, the charts always have the camera's vertical pixel dimensions as their height so you can get a good idea of how lenses compare.

In the charts below the Sigma tops out right at the top of its chart but the Canon reaches only half way up the top division, so the Sigma will give better resolution at its best aperture on any camera. But wide open they are both just below the top of the second division so that advantage disappears when the lenses are opened up.

The Nikkor 85s (1.4, 1.8) follow the same pattern. PZ hasn't reviewed the Sigma 50/1.4 Art so I can't show that but its ordinary 50/1.4 starts very soft wide open.

yes. The older sigma is an entirely different discussion.

True.

As are those Nikkors that I did not mention

No; you assumed the OP was talking about Canon-mount lenses; but I don't see that in his post. But even if he is, the pattern of resolution I describe is common across makes.

Note that PZ shows resolution on bands that relate to the pixel density of the camera used to test so the numbers aren't comparable but the shape (towards the top of "very good") is.

so different bodies?

Yes, but see above for why that doesn't matter/

Do you misunderstand me? I was not stating that many other lenses are at there very optical best wide open.

"There are more advanced designs that are better wide open."

No - or, more accurately, I understood you to be saying one of two things:

(1) There are some lenses that are better wide open than they are stopped down. I had already said the same thing "A very few lenses are sharpest wide open but even they suffer some diffraction softening." Although the best I've found - Zeiss Batis 85/1.8 is a fraction softer at d/1.8 than at f/2.2 (again according to PZ).

(2) There are some lenses that are better wide open than the lenses the OP is using. That's certainly true - as the Sigma 85/1.4 Art shows - bit wide open it's not a lot better. Its advantages show up after it's been stopped down a bit.

well I can see how I am confusing. Perhaps I should have said "give you better results wide open"

That would have had the same ambiguity.

The Nikkor 85s are equal to each other at f/1.8; the Sigma 85/1.4 Art is about 6=7% sharper. That's not what I'd call "a lot better" - it's often said that the "just noticeable difference" for resolution is 10-15%.

I didn't mention the Nikkors.

True, but see what I wrote earlier.

I also don't know if it is entirely fair to compare 1.4 and 1.8 lenses at their different wide open apertures equally.

It is entirely fair. The OP wants to know if he can get sharper results at f/1.8. Any lens that is f/1.8 or wider can work at f/1.8., so that's the aperture to consider.

Any other sites?

Several. You can search as easily as I can.

I know everyone hates this one

The way DxOMark presents its results makes it very hard to isolate performance at specific f-stops.

https://www.dxomark.com/lenses/bran...dOptions=false&viewMode=list&yDataType=global

If I have made a mistake please correct me.

See above.

Perhaps "much better" was a harsh term. I will take "better".

If you'd said that to begin with the discussion would have been different.

--
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Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006
http://www.pbase.com/gerrywinterbourne
[email protected]

 

[Gerry Winterbourne]

A very few lenses are sharpest wide open but even they suffer some diffraction softening.

How can I get sharper images at wider aperture ?

You can't get any better resolution - it's the nature of lens optics.

With those lenses. There are more advanced designs that are better wide open. I am assuming the Canon eF?

The sigma art 50 and 85 look a lot better wide open. You will pay for the luxury

These are screen shots of the Sigma 85/1.4 Art and Canon EF85/1.8 from the Photozone reviews. Both follow the pattern I described.

...

Do you misunderstand me? I was not stating that many other lenses are at there very optical best wide open.

"There are more advanced designs that are better wide open."

well I can see how I am confusing. Perhaps I should have said "give you better results wide open"

I presume that Gerry meant that lenses are better stopped down a bit then the same lens wide open, while you meant that some lenses are better wide open than other lenses are wide open, but you have been misinterpreted to mean that some lenses are better wide open than the same lens stopped down a bit.

Read my follow-up reply to golfhov. There's nothing in either of my posts to support your idea that I misinterpreted what he said; I simply disagreed with it.

 

[golfhov]

A very few lenses are sharpest wide open but even they suffer some diffraction softening.

How can I get sharper images at wider aperture ?

You can't get any better resolution - it's the nature of lens optics.

With those lenses. There are more advanced designs that are better wide open. I am assuming the Canon eF?

The sigma art 50 and 85 look a lot better wide open. You will pay for the luxury

These are screen shots of the Sigma 85/1.4 Art and Canon EF85/1.8 from the Photozone reviews. Both follow the pattern I described.

...

Do you misunderstand me? I was not stating that many other lenses are at there very optical best wide open.

"There are more advanced designs that are better wide open."

well I can see how I am confusing. Perhaps I should have said "give you better results wide open"

I presume that Gerry meant that lenses are better stopped down a bit then the same lens wide open, while you meant that some lenses are better wide open than other lenses are wide open, but you have been misinterpreted to mean that some lenses are better wide open than the same lens stopped down a bit.

I know everyone hates this one

I don't hate it. . The data at the following link show that the Sigma 50mm Art is much sharper stopped down to f/1.8 than it is wide open at f/1.4, and even sharper at f/2, f/2.8 and f/4. This is the effect that Gerry described. The data also show that the Sigma 50mm Art wide open at f/1.4 is sharper than the Canikon 50mm f/1.4 lenses are wide open at f/1.4. So you are both right.

https://www.dxomark.com/lenses/bran...dOptions=false&viewMode=list&yDataType=global

If I have made a mistake please correct me. Perhaps "much better" was a harsh term. I will take "better".

I think the confusion lies in what is being compared to what.

 

[golfhov]

"Some lenses perform better at 1. 4/1.8 than others" There is often a price and weight penalty for this"

Better?

My ONLY issue with your statement was it came off as if "good" results are not possible at wide apertures. With certain lenses this is largely true because they are notoriously soft at their widest apertures. Some designs are not "at their best" wide open but still produce very "good" results

 

[Tuloom]

How can I get sharper images at wider aperture ?

You buy better lenses.

 

[hotdog321]

When I use the little 50mm f/1.8 at f/1.8 ~ f/2.8 the images are a bit soft at center and get softer / more blur at the corners .

But when using f/3.5 ~ f/11 the images are sharper and less blurred .

Even with 50mm f/1.4 and 85mm f/1.8 , when using wider aperture , the images become less sharper .

How can I get sharper images at wider aperture ?

This is normal behavior for almost all lenses. Ignoring depth of field issues, just about all lenses are sharpest when stopped down 2-3 stops from wide open. For instance, a f/2.0 lens will likely be sharpest at f/4 or f/5.6. There are all kinds of optical reasons, but just accept it as a universal truth.

 

[Mark S Abeln]

semi pro photographer wrote: .

How can I get sharper images at wider aperture ?

At wide apertures, focus can be difficult, and even sharp lenses can deliver images that look soft if the subject focus is off.

DSLRs that have a separate phase focus sensor can be miscalibrated, leading to systematic focus errors. With any kind of focus system, if the focus point is misplaced, or if the subject is strongly 3-dimensional under the focus point, or if you move the camera after focusing (such as when doing focus-and-recompose) then focus errors can happen.

Furthermore, some optical defects in lenses can make focus more error-prone.

Also the depth of field at such wide apertures can be so narrow that much of the subject is defocused and so appear soft.

Finally, you can always add sharpening to your images to make them look crisper,