Incense

by Bart Arondson

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11

The main reason we don't have "super zooms" with a large constant aperture is size/weight/costs. Roger at LensRentals recently blogged about this in the post: About That 25-300mm f/2.8 You Wanted About How Big is that? The lens is in a video housing, so that makes it a bit larger than an SLR designed lens of the same specifications would be. But ...


7

It doesn't look too bad to me. You have to consider that when you're looking at a 5D mkIII image at 100%, that amounts to a considerable enlargement. It's rare to get something really pin sharp at that magnification. The focus point is quite forward so the trees in the centre of the frame are at or near the far limit of the DOF. That combined with the ...


6

It is more about ratios than addition/subtraction. 70-200mm is less than 3x from the shortest to longest focal length. 18-135mm is 7.5x. The higher the ratio between the shortest and longest focal length, the greater the difference between the "effective aperture", more properly called entrance pupil, for the shortest and longest length at the constant ...


5

According to a related discussion on dpreview: A lens can be made physically shorter than its focal length by the use of additional lens elements called a telephoto group. According to the Wikipedia page for Telephoto lens: The basic construction of a telephoto lens consists of front lens elements that, as a group, have a positive focus. The focal ...


5

The blur can be measured by converting to XYZ colorspace and zooming into a tree trunk with a bright sky as the background. You then measure the brightness profile accross the rapid change in brightness (make sure you pick an area with small gradient in the direction parallel to the tree trunk). I then used this method to estimate the blur. Since the image ...


2

I can't look at the RAW image at the moment, but it should be fairly sharp, but likely won't be pixel sharp on a 5D Mark iii at 100% magnification. The 24-70 f/4L isn't a prime lens and it isn't the f/2.8II. It isn't as strong of an optical performer and 22mpix is a lot of image data. (I use the f/2.8 II on my 5D Mark iii regularly.) The f/2.8II will come ...


2

There are two hard limits on how fast a lens can be: The first is a thermodynamic limit. If you could make a lens arbitrarily fast, then you could point it to the sun and use it to heat your sensor (not a good idea). If you then get your sensor hotter than the surface of the Sun, you are violating the second law of thermodynamics. This sets a hard limit at ...


2

Just to give another (maybe wrong) view on this, I think what is being referred to as the Leica look is a mixture of subjective and objective things. There are some photographers that are so used to review, make, create, and study pictures taken with Leica lenses and cameras that can identify the lens a picture was taken with. I know it may seem disturbing, ...


2

There are several approaches to getting a lens system with a long focal such that it is closer to the media than its focal length. The most common of these is the 'telephoto' lens From Wikipedia: https://commons.wikimedia.org/wiki/File:Lens_telephoto_1.svg What this does is it that the outer lens element (at the front of the lens system) has a positse ...


1

Making a lens shorter than a simple lens is exactly what the term telephoto means. Telephoto groupings basically act kind of like a magnifying glass, making the field of view close faster than would happen with a simple lens system. Traditional telephoto lenses still required a fair bit of space and lots of lenses to operate, but newer things like ...


1

The problem with any attempt to reverse optical blurring by estimating/modelling the point spread function is noise. In principal if you know how the lens blurs an image and have an accurate version of the blurred image you can reconstruct the original "unblurred" image. But in the presence of noise you don't really have the blurred image, you have the ...


1

I think different people will have different definitions, but the so called Leica look has been often associated with the look produced by lenses created by Walter Mandler. No lens is perfect and each designer needs to decide their priorities and set of compromises they are willing to make. Mandler selected the compromises in a way that differed from ...



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