Part one
Originally posted by normhead ANd how is this different than just looking a lens chart, noting where the lens is sharpest and the rate at which it falls off, and shooting accordingly?
It’s not about knowing where the lens is sharpest or the rate if falls off. As I have stated over this thread several times I want to know where diffraction blur, defocus blur and finally the resolution blur all intersect. Why this is important is this directly influences how much you stop down the lens and where you set you hyper focal distance for a given DOF. With also knowing how these blurs interact we can use a model that is a best fit it to a known output size and optimism that based on the cameras resolution, this can greatly reduce shutter speeds for times you are shooting under limited light conditions or as I have shown in the 24mp vs 36mp an increase in DOF without the penalty to captured resolution.
There is really only 3 way you can derive where the intersection of these blurs occur at the same rate. One a user has to map out this intersection of these3 blurs for every minimum acceptably sharp over varying distances, that person would then also have to work that out for every FL that person might use in landscape photography and keep notes on these mapped models. The second would be that the photographer would have to adjust the f/stop, select the best hyper focal distance for that f/stop (which is different than the standard hyper focal distance chart), then check and see if everything you want falls within that DOF. This would have to be repeated over and over until you find this balance. The 3rd and final would be to base the above on a mathematical model that tells you where these 3 blurs equal out.
Originally posted by normhead Lens charts tell you that for most of your lenses they are going be sharpest at ƒ5.6 and fall off from there. So you shooting starting at ƒ5.6 and use whatever Aperture gives you the DoF you want? If you shoot for shallow DoF then you select on how shallow you want it to be.
The problem with this is that when balancing DOF with diffraction and captured resolution is the camera resolution greatly affect how much DOF you can capture. The reason why I state captured resolution it is that this always limits us to how much we stop down the lens in landscape photography.
Originally posted by normhead I'm not seeing how the AP helps or even works. In your example you ended up using an exposure I could have used. I was hoping you had one that was something I wouldn't have anticipated. Going back with a higher resolution camera next year I'd shoot the same settings, and using a 3 step bracket. Then I'd pay careful attention to the images to see what worked best.
The problem is that exposures does not give us a known DOF, and how will you know where to focus based on those 3 bracketed shots, would you even adjust the where the camera focus’s?
Originally posted by normhead I'm not understanding why this has to be so complicated. I can only assume that when you don't use the app, you mess up a lot images.
So weren’t you that made the statement above? So now for you to get the best out of a higher resolution body you would resort to messing up a lot of images to get the correct images? See the app will alleviate how much work it takes to balance the DOF for the scene.
My answer I would be simply to shoot at f/16 and set the hyper focal distance at half the distance from the camera as the year before.
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Part two
Originally posted by normhead Maybe you could point us to a reference for this. As far as I know DoF is defined pretty much by circles of confusion,
CoC is a mathematical model that defines how a DOF calculator will model DOF, for a give f/stop and focal plane distance, this is based on whatever the users has decided the final output resolution.
Basically with any DOF calculator you must first model and define what acceptably sharp is so that the DOF calculator can formulate a DOF and hyper focal distance. For a standard and most commonly use model is CoC 0.03, so what this tells the DOF calculator is that any resolution being projected onto the sensor plane that falls on at or smaller than 0.03mm will be considers as acceptable sharp for an image that is viewed at that models (CoC) output resolution and viewing conditions. The problem is that many cameras can resolve details that are 10 times smaller than that.
Originally posted by normhead which are going to be the same size regardless or the number of Mega Pixels.
This is correct that CoC model of what is acceptably sharp remains the same. I think you are hinting at CoC the lens projects, If this is what you are hinting at lets differentiate that from the CoC that is used in modeling DOF for the calculator and call it airy disk or diffraction blur.
Originally posted by normhead Diffraction and CA are usually reported by the pixel size, so as pixels get smaller CA and Diffraction become worse pixel peeping. Once you get over the size where CA crosses multiple pixels it does a lot more damage to image resolution. Same with diffraction.
One of the problems many people are under the assumption that after a certain f/stop that increased resolutions at this alleged diffraction limit that you are not going to capture more resolution This really isn’t what happening, take the
50mp camera at f/11 can capture more resolution than a 24mp camera can at any f/stop and that’s well into effects of where you start to see diffraction lessening your captured resolution.
This is why with a camera that can capture more resolution you can capture more DOF.
How this plays out in the real world at very commonly used airy disk sizes we see very different levels of resolution being captured with different cameras resolutions.
This is why it helps to know how diffraction blur, defocus blur and resolution blur relates to captured resolution as this will determine how you will stop down and focus the lens.