[alamo5000]

I sometimes hear people on the board here refer to a lens "sweet spot"...

I am not a noob, but more information on specifically what this really means would help (as well as how to determine this information for my specific lenses).

I assume the 'sweet spot' is the aperture range where the lens is most sharp? Of course each lens has it's own personality as to where it's best. Or is it more than that?

I think it would be useful to write down and have this information for my particular lens collection. Mainly so I can use what I am being told and try to better self evaluate and examine my shots so in the end I can make better photography decisions.

Here is my lens list. DA 15mm, DA 21mm,F28 f2.8, FA 31mm, DA 40mm, FA 43mm, F50 f1.7, DA 70mm and a Tamron 70-200 f2.8 (I don't know if zooms have a sweet spot as much as primes do because of the varying focal length and aperture combination)

List away!

I sometimes hear people on the board here refer to a lens "sweet spot"...

I am not a noob, but more information on specifically what this really means would help (as well as how to determine this information for my specific lenses).

I assume the 'sweet spot' is the aperture range where the lens is most sharp? Of course each lens has it's own personality as to where it's best. Or is it more than that?

I think it would be useful to write down and have this information for my particular lens collection. Mainly so I can use what I am being told and try to better self evaluate and examine my shots so in the end I can make better photography decisions.

Here is my lens list. DA 15mm, DA 21mm,F28 f2.8, FA 31mm, DA 40mm, FA 43mm, F50 f1.7, DA 70mm and a Tamron 70-200 f2.8 (I don't know if zooms have a sweet spot as much as primes do because of the varying focal length and aperture combination)


List away!

I own the DA 40 only; it is one of the few lenses I know to be very sharp from the very outset, so I never felt the need to seek out the 'sweet spot.' As a general rule, the mid-range apertures will give you the sharpest images.

[carrrlangas]

I think it´s non-sense. One should use the ** aperture value that provides enough DoF, keeps shutter speed ok, and/or helps achieve a desired effect (i.e. reduce flare, starbursts). Replace ** for "largest" in order to avoid diffraction resolution loss.
From the lenses you listed, I can say they are all "sweet" form their widest aperture (expect FA43 and Tamron zoom which I´ve never tried)

If sweet spot means sharpest, then I´d say get better lighting setup. Be it natural or artificual, hoods, position, etc.

I think it´s non-sense. One should use the ** aperture value that provides enough DoF, keeps shutter speed ok, and/or helps achieve a desired effect (i.e. reduce flare, starbursts). Replace ** for "largest" in order to avoid diffraction resolution loss.
From the lenses you listed, I can say they are all "sweet" form their widest aperture (expect FA43 and Tamron zoom which I´ve never tried)

If sweet spot means sharpest, then I´d say get better lighting setup. Be it natural or artificual, hoods, position, etc.

It is not non-sense. You are talking about what is practical from the vantage point of one's desired aim, whereas he was talking about 'sweet spot' or sharpness as such. Getting a 'better lighting setup' has got nothing to do with the merits of a lens.

[carrrlangas]

It is not non-sense. You are talking about what is practical from the vantage point of one's desired aim, whereas he was talking about 'sweet spot' or sharpness as such.

But how could we define a "Best compromise between sharpness and diffraction, contrast, specular highlights, aberrations, flare rendering, etc" / "sweet spot" without taking lighting into account. Any modern premium lens as the ones he listed are capable of performing in good (adequate) lighting setups from their widest aperture.
So, should we choose an aperture value that is good enough in most light conditions or set different sweet spots for each lighting situations?

But how could we define a "Best compromise between sharpness and diffraction, contrast, specular highlights, aberrations, flare rendering, etc" / "sweet spot" without taking lighting into account. Any modern premium lens as the ones he listed are capable of performing in good (adequate) lighting setups from their widest aperture.
So, should we choose an aperture value that is good enough in most light conditions or set different sweet spots for each lighting situations?

You are conflating the circumstantial with the essential, or to use Aristotelian terminology: the accidental with the substantial. And while you are at it, why not take into account more extreme and unsual lighting conditions as well? The lenses he mentioned do not perform optimally at all apertures, and any test of these lenses found online will serve to confirm this fact. The general rule has always been that lenses tend to peak at their mid-range apertures; I did not invent this rule - these were the findings of those who know the science of photography.

[alamo5000]

For me, my lenses are plenty sharp. Sharp isn't my problem I probably *should* be asking more about lighting and composition, getting better subject matter and all sorts of things...but in this case I am asking more specifically about *lenses* and their specifics... or rather people's opinions about them.

Yes, my lenses are plenty sharp. I am not complaining a bit. I am just curious as to what this whole 'sweet spot' thing that people keep talking about means or what they consider 'sweet spots' for a specific lens (that is on my list).

I hear the term 'sweet spot' and I really don't know what people mean by that.

[johnyates]

I hear the term 'sweet spot' and I really don't know what people mean by that.

Stopping down a lens reduces the aberrations. Stop down too far and you get diffraction. The sweet spot is where aberrations are reduced as much as possible and diffraction has yet to kick in. <= my undertanding of 'sweet spot'

Rule of thumb: stop down two to three stops from wide open to get the very best performance from a lens.

[Driline]

I hear the term 'sweet spot' and I really don't know what people mean by that.

Simple. Minimum F stop for corner to corner sharpness. Photozone.de talks mentions this on almost every lens they evaluate. For example the FA 31 is F2.8.......at least that's my interpretation. And as a card carrying member of Mensa how could I possibly be wrong?

[6BQ5]

The "sweet spot" typically refers to the combination of aperture and focal length that produces the sharpest images. That means the convergence of light has reached a maximum. A lens ought to be at its sharpest at maximum aperture since there is no diffraction. In reality you have uncollimated light coming in from every which way and the lens cannot make light from every vector converge. Closing down the aperture a bit filters out some of the light and helps collimate it too. With the light rays more parallel the lens can then focus them and converge them into a sharp image. All of this comes at the expense of diffraction. Even if it imperceptible to our eyes or the sensor/film, the effect is still there. If you close down the aperture more and more you will have more and more collimated light but at the expense of rising diffraction. At some point the diffraction becomes noticeable. Take f/22 as an extreme example. You have very large depth of field but the image is a bit soft due to diffraction.However, at f/5.6 to f/8 you may have a reduced depth of field but less diffraction. So, the image will look sharper. Take that with a grain of salt. In some cases, like dreamy blurred water waves, the diffraction won't matter. The subject us blurred on purpose to begin with!

This why higher resolution image sensors can induce a strain on older lenses. Smaller resolution sensors have photo sites that are larger than some of the aberrations. The larger resolution sensors will resolve every little defect a lens puts out! That is one reason lenses can be so expensive. The glass has to be near perfect! That is also why some vintage lenses are highly prized. They were built right the first time around!

The sweet spot of every lens is different and it takes some experimentation to find it. Sometimes online lens tests help too but use them as guidelines. Some lenses start their sweet spot from wide open while others need to be stopped down a bit. My DA 40mm XS is damn near perfect wide open but my FA 28-200mm super zoom only renders razor sharp images at f/11. Two extremes!

[ak_kiwi]

"Sweet spot" is sometimes used to describing the best of part of the image circle.
E.g "The K-3, being aspc, gets to use the 'sweet spot' of this lens which can sometime show border softness when used with a full frame camera"

[reeftool]

Generally, the 'sweet spot' is the aperture where the lens is the sharpest. A good lens is going to be sharp throughout until it gets to the point where diffraction becomes an issue. The sweet spot issue is much more common in consumer grade lenses. An example I will give is my cheap Sigma 70-300. It's at it's best from f/8-f/11 with f/11 having the best results. At other apertures, the IQ isn't all that great although you can usually make up for it in PP. Not to be confused with depth of field as I'm speaking about the in focus area. It's also a bit subjective. When you use a lens over a period of time, you discover it's better at some subjects and light and not as good for others.

One problem you can run into on lens reviews is paying too much attention to "sweet spot" comments. A lens may be it's sharpest on a test chart at f/6.3 but you may not get the result you desire at that aperture. A lot of great landscapes are shot at f/16 which is well into diffraction territory on our lenses but it's really not noticeable unless you pixel peep a 100% crop of a corner and you won't see it at all on a print. Then there is the issue of the "soft" lenses like the 85/2.8. Try defining the "sweet spot" on a specialty lens like that. Making a "sweet spot" list from other peoples comments won't work. One of the lenses you list is the DA 40/2.8. I have that lens. I use it almost exclusively for people shots at parties and events and mostly wide open. The sweet spot most people will mention for that lens isn't going to f/2.8 but that's what I use it for and it's better at f/2.8 than anything else I own.

Simple. Minimum F stop for corner to corner sharpness. Photozone.de talks mentions this on almost every lens they evaluate. For example the FA 31 is F2.8.......at least that's my interpretation. And as a card carrying member of Mensa how could I possibly be wrong?

I have occassionally found some striking variances between the findings of photozone and ephotozine in this regard. Hence I think it would be better to trust on one's own judgement all the while respecting conventional wisdom rather than rely on the scientific lingo all too common in modern photography forums.

[ak_kiwi]

This why higher resolution image sensors can induce a strain on older lenses. Smaller resolution sensors have photo sites that are larger than some of the aberrations. The larger resolution sensors will resolve every little defect a lens puts out! That is one reason lenses can be so expensive. The glass has to be near perfect! That is also why some vintage lenses are highly prized. They were built right the first time around!

Thanks for that. I originally thought my K-3 was noisy until I got some ltd lenses. Until now I was not aware why I was seeing such a difference in lenses used.

[alamo5000]

Stopping down a lens reduces the aberrations. Stop down too far and you get diffraction. The sweet spot is where aberrations are reduced as much as possible and diffraction has yet to kick in. <= my undertanding of 'sweet spot'

Rule of thumb: stop down two to three stops from wide open to get the very best performance from a lens.

Aberations: Define

Diffraction: Define

Please (for the sake of conversation) define those two words in laymans terms and how they negatively impact my pictures