Let's talk lens "sweet spots"

[NateNLogansDad]

What I'm curious about is aperture and focal length.

If I remember correctly, the "Sweet spot" is usually around the mid F-stop on a lens. (Is that correct?) If I picked up a lens that was 18-55mm and 2.8 all the way through, and let's say the sweet spot was considered around F/8 would that be true all the way from 18mm to 55mm or would it vary a stop or two?

Would the same apply for something more on the longer end, like for a 70-200 2.8?

 

[ukcatfan]

I always heard that the sharpest focal length of a zoom lens is right around the middle, so around 35mm in your 18-55mm example. I have also heard that the sharpest aperture is around 2.5-3 stops down from wide open. I believe that would only change on variable aperture lenses. I personally only worry about this stuff when setting up for general snapshots. For more creative shooting, I pick the aperture for the effect and don't worry about sharpness.

 

[thomas998]

Unless you are planning on making really big prints or plan on cropping down to very small selections of a photo... I wouldn't worry about the sweet spot. I've seem people yammer endlessly about the correct number of stops to go for a lens to get the sharpest image possible... some will even buy very fast lenses and never use them wide open because they believe that wide open it isn't as sharp as possible... I've never really had a problem with shooting wide open other than when the lens is out of focus... I even recall a article I once read once that included test photos shot wide open and stopped down to the "sweet spot", and the funny thing is, unless you were going to make a poster size print or were looking at a sliver of the actual photo there was no real different in sharpness.

I would worry more about what I liked and less about mythical "sweet spots".

 

[wbeem]

I would worry more about what I liked and less about mythical "sweet spots".

Agreed. Unless you're mounted on a tripod with mirror-lockup, your hand will likely cause enough vibration to mask the difference between one aperture and another. Pixel peeping may be technically satisfying, but it doesn't mean you have a great picture.

Also, remember that if you shoot in RAW mode, you still have to go back and sharpen your images in post, anyway.

 

[photo_chick]

The sweet spot does make a difference with some lenses, especially with fringy lenses. Others, not so much. On a zoom lens a lot of people consider it to be at a specific place in both focal length and aperture. And it's usually somewhere in the middle. But if you spend your time chasing those numbers you'll miss out on a lot.

Nailing the focus in camera and getting good contrast when you edit will do a whole lot more for the sharpness of your images than anything else will. Get those right and you may find that you don't need to sharpen anymore. Not even RAW files.

 

[Marlton Mom]

The sweet spot does make a difference with some lenses, especially with fringy lenses. Others, not so much. On a zoom lens a lot of people consider it to be at a specific place in both focal length and aperture. And it's usually somewhere in the middle. But if you spend your time chasing those numbers you'll miss out on a lot.

Nailing the focus in camera and getting good contrast when you edit will do a whole lot more for the sharpness of your images than anything else will. Get those right and you may find that you don't need to sharpen anymore. Not even RAW files.

+1
.... and if you go to sites that test the lenses you can read up on where the lens is 'naughty' and where it 'plays nice'.

http://www.slrgear.com/reviews/showcat.php/cat/2

~Marlton Mom

 

[wbeem]

Nailing the focus in camera and getting good contrast when you edit will do a whole lot more for the sharpness of your images than anything else will. Get those right and you may find that you don't need to sharpen anymore. Not even RAW files.

I was just looking at some of my shots from last weekend. F/2.8 and sharp right where I wanted it, right out of camera. However, a little targeted sharpening in Photoshop just makes it that much better.

Do you need to sharpen more? Maybe not, but why not make the best image instead of one that's just good enough?

 

[NateNLogansDad]

Thanks for all the replies!

I do want to stick up for myself a tad bit though. I didn't start this thread because I'm obsessed with the sharpest possible image, I'm just naturally curious on how certain things work.
If I was that obsessive, I'd be using a tripod instead of handheld.....or at least put my drink down

 

[NateNLogansDad]

+1
.... and if you go to sites that test the lenses you can read up on where the lens is 'naughty' and where it 'plays nice'.

http://www.slrgear.com/reviews/showcat.php/cat/2

~Marlton Mom

Thanks for that link. I started reading some things on my 18-250 and a few times I had an kind of moment.

 

[boBQuincy]

If I was that obsessive, I'd be using a tripod instead of handheld.....or at least put my drink down

Never put down the drink, photography is not *that* important!

One thing I noticed about the 18-200 lenses is that all of them are pretty wretched at some focal lengths, often around 135. LensRentals has a good article about how all of our lenses have evolved from a small number of basic designs so it is not surprising that even across brands many lenses share some of the same faults.

 

[wbeem]

Thanks for all the replies!

I do want to stick up for myself a tad bit though. I didn't start this thread because I'm obsessed with the sharpest possible image, I'm just naturally curious on how certain things work.
If I was that obsessive, I'd be using a tripod instead of handheld.....or at least put my drink down

Wait, you had a drink? That was my complaint last time shooting fireworks in front of the castle - no cocktail service.

 

[pointandshoot]

Never put down the drink, photography is not *that* important!

I am putting that on a t-shirt and wearing it the next time I go to Food and Wine.

 

[NateNLogansDad]

Never put down the drink, photography is not *that* important!

One thing I noticed about the 18-200 lenses is that all of them are pretty wretched at some focal lengths, often around 135. LensRentals has a good article about how all of our lenses have evolved from a small number of basic designs so it is not surprising that even across brands many lenses share some of the same faults.

Is that in their blog somewhere? I'd like to look it over.

 

[NateNLogansDad]

Wait, you had a drink? That was my complaint last time shooting fireworks in front of the castle - no cocktail service.

I always have a drink.

This last trip I was part of a group of 25 that I was related to by marriage. Yes, I had a drink.... and another, and another, and another.

 

[NateNLogansDad]

I am putting that on a t-shirt and wearing it the next time I go to Food and Wine.

You jest, but I think that's an awesome idea! I'm going to have to look into this one!

 

[NateNLogansDad]

Never put down the drink, photography is not *that* important!

Do we have permission to put this on some t-shirts? I'd like to get my wife to make up some iron-on's!

 

[theduck619]

You jest, but I think that's an awesome idea! I'm going to have to look into this one!

I would buy one

 

[boBQuincy]

Do we have permission to put this on some t-shirts? I'd like to get my wife to make up some iron-on's!

I hereby grant all Disboard photographers full permission to use this bit of wisdom on t-shirts, etc. Btw, I use CustomInk for my custom t-shirts.
Who knows, it could be a movement, with hundreds of photographers showing up at Epcot with remote releases attached to their drink holders!

 

[wbeem]

I always have a drink.

This last trip I was part of a group of 25 that I was related to by marriage. Yes, I had a drink.... and another, and another, and another.

Now I know what I've been doing wrong. If I can't hold my drink, I need to bring someone who can hold it for me.

 

[NateNLogansDad]

Now I know what I've been doing wrong. If I can't hold my drink, I need to bring someone who can hold it for me.

I need someone who knows how to use my camera.

The drinks I can manage