[eyespywithmyi]

Is there a chart somewhere that lists all the Pentax lenses and their aperture sweet spot?

[pschlute]

no, but f4-f8 covers it

[c.a.m]

Is there a chart somewhere that lists all the Pentax lenses and their aperture sweet spot?

In late 2015, member @BigMackCam presented his compiled set of Lens Resolution Profiles, which you might find useful: Pentax lenses - Resolution performance at various apertures - PentaxForums.com

Please note that the charts indicate lens resolution (aka 'sharpness'), which is a key parameter. Other optical characteristics such as distortion, vignetting, or aberrations, also which can vary by aperture, are not included.

I find that his method of illustrating the data is particularly easy to grasp and visualize. He put quite a lot of work into this project (many thanks, again !).


- Craig

[eyespywithmyi]

In late 2015, member @BigMackCam presented his compiled set of Lens Resolution Profiles, which you might find useful: Pentax lenses - Resolution performance at various apertures - PentaxForums.com

Please note that the charts indicate lens resolution (aka 'sharpness'), which is a key parameter. Other optical characteristics such as distortion, vignetting, or aberrations, which can vary by aperture, are not included.

I find that his method of illustrating the data is particularly easy to grasp and visualize. He put quite a lot of work into this project (many thanks, again !).

- Craig

Amazing! Looking forward to diving into that. I started learning digital photography about 9 months ago, I'm experimenting more with different variables and settings but it will be nice to have a general guide and starting point. Last month I was photographing a bird I'd never seen before and I took about million photos of it, using every combination, to make sure I got at least a couple good ones. Luckily the bird was taking an extended nap... Thanks!

[normhead]

Amazing! Looking forward to diving into that. I started learning digital photography about 9 months ago, I'm experimenting more with different variables and settings but it will be nice to have a general guide and starting point. Last month I was photographing a bird I'd never seen before and I took about million photos of it, using every combination, to make sure I got at least a couple good ones. Luckily the bird was taking an extended nap... Thanks!

For birds with long glass, ƒ5.6 or ƒ8 you won't have enough shutter speed to avoid motion blur with less.
For wide angle normal glass, ƒ5.6 is usually sharpest.
For telephoto ƒ8.

I usually hang around those two f-stops, unless I need faster for low light or background blur, or a narrower aperture for more DoF.

[eyespywithmyi]

For birds with long glass, ƒ5.6 or ƒ8 you won't have enough shutter speed to avoid motion blur with less.
For wide angle normal glass, ƒ5.6 is usually sharpest.
For telephoto ƒ8.

I usually hang around those two f-stops, unless I need faster for low light or background blur, or a narrower aperture for more DoF.

For birds I primarily use the D FA 150 mm-450 mm and have it wide open 99% of the time, I'll try it stopped down a touch but it's hard enough as it is to hold it still at 4.5 with my delicate lady arms, haha.


Thanks for the others, too, will be trying all these tips out.

[northcoastgreg]

Sweet spot where? In the center—or along the edges and corner? Because they're not necessarily the same. Older glass may need to be stopped down a bit, because wide open it may not be "sharp."

With newer glass, this concern with the "sweet spot" is less important. A lens like the DA 55-300 PLM, for example, is already pretty sharp wide open, and doesn't get all that much sharper stopping down. I would hazard to guess that these new DFA* primes can be safely used at any aperture. With such glass just use whatever aperture is best suited for the image you're taking and stop worrying about "sweet spot."

According to MTF Line, the Tamron 70-200 is sharpest at f4 from 70mm nearly to the long end of the lens, and then sharpest at 200mm at f4.5. But if I'm using that lens for landscapes, I'm probably going to stop down to f11 or more, because I need the depth of field and I want sharper corners. Is f11 as sharp as f4 with that lens (in the center)? No, but there's really not much difference. And a landscape taken at f4 with a telephoto lens may have large areas out of focus because of the narrow depth of field, so in that sense f11 may in fact be "sharper" through the overall image (although it isn't sharper in "testing" sense, where lines on a piece of paper are photographed, rather than a subject or scene in the real world).

[MossyRocks]

After looking at the old post from BigMackCam for the lenses I own my gut feel from looking at shots I've taken with the lenses I own match up pretty nicely even if I've never actually tested them.

That said very rarely dose where the lens is sharpest come to mind when setting up for a shot. In most circumstances what I have is sharp enough and the few lens that have sharpness issues wide open (17mm fisheye takumar, SMC A 50/1.2, Vivitar Series 1 135/2.3) it is either because the ability to make an ultrawide fisheye that was super sharp wide open well didn't exist when the lens was designed or was probably a design choice (50/1.2 and 135/2.3). If I want an ethereal feel the 50/1.2 has it in spades wide open and the Vivitar Series 1 135/2.3 has a smoothness wide open that I can see how it would be wanted for portraits. Beyond those 3 lenses the only time I care about where a lens becomes sharpest is when I'm doing astrophotography but that is its own special usecase as under most circumstances most even somewhat modern lenses are sharp enough.

Things like missed focus, subject movement, camera movement, etc are all bigger bigger issues for me than how sharp a lens is.

[baro-nite]

Also look up "Program Line", a setting for certain exposure modes that can be set to MTF Priority. This will automatically pick the sharpest aperture (requires a relatively recent lens: FA, DA, D-FA).

[normhead]

Things like missed focus, subject movement, camera movement, etc are all bigger bigger issues for me than how sharp a lens is.

Especially since I'm not convinced that at my normal level of image reduction, there's a difference between ƒ4 and ƒ11. It's all about shutter speed and DoF.

[eyespywithmyi]

Things like missed focus, subject movement, camera movement, etc are all bigger bigger issues for me than how sharp a lens is.

I guess I was looking for excuses other than user error and my inability to hold the 150 mm-450 mm still. I'm getting better at it but was hoping perhaps there was a silver bullet (other than a tripod and/or stronger arm muscles).

[normhead]

I guess I was looking for excuses other than user error and my inability to hold the 150 mm-450 mm still. I'm getting better at it but was hoping perhaps there was a silver bullet (other than a tripod and/or stronger arm muscles).

For birding I always use a tripod for my heavy lenses.... and all the lenses below have shake reduction, but they are also doing the same. For birds I never lock the tripod, I just use it to steaddy the lens enough so the SR can do its thing.



SR is not sufficient to pass on a tripod for long lenses. You can go without a tripod for 10 minutes when necessary, but it's not an all day kind of thing.

[eyespywithmyi]

SR is not sufficient to pass on a tripod for long lenses. You can go without a tripod for 10 minutes when necessary, but it's not an all day kind of thing.

I tried a monopod for the first time yesterday, with the ball-head just loose enough that I could follow the movement of the bird. I did find myself getting frustrated at having limited freedom of movement with the monopod, but I also finally got a sharp photo of a bird I'd been trying to capture for over month!

[ramseybuckeye]

I tried a monopod for the first time yesterday, with the ball-head just loose enough that I could follow the movement of the bird. I did find myself getting frustrated at having limited freedom of movement with the monopod, but I also finally got a sharp photo of a bird I'd been trying to capture for over month!

I'm impressed with getting any tern in flight.

[Paul the Sunman]

For birds I primarily use the D FA 150 mm-450 mm and have it wide open 99% of the time, I'll try it stopped down a touch but it's hard enough as it is to hold it still at 4.5 with my delicate lady arms, haha.

Have you tried a monopod?