Serene Life

by garik

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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 ...


The action of zooming the lens is nearly identical to the action of reloading a pump-action shotgun: slide the barrel forward and backward. Back in the days before autofocus this was the preferred zoom lens mechanism. The two-ring lenses required you to move your hand between the zoom ring and the focus ring which took time. Some preferred the precision of ...


Here is an example image of a 'pump zoom', this is the Canon 100-400mm IS USM:


It just means you push / pull the front of the lens to zoom, rather than twisting a zoom ring. The mechanism is simpler to design/manufacturer but is less precise and has a reputation for sucking dust into the lens due to the large change in volume when zooming.


I recall one of the Canon reps giving a talk at B&H (the talk is on Youtube, but I'm not sure which one; probably the 5DIII/1DX videos) and he addresses the weather sealing. His advice was that it's weather "sealing" and not weather "proofing" so if you need a jacket, so does your camera. Personally, it doesn't matter. This is a somewhat useless feature ...


I use Canon Cameras and at first, I was also in the same dilemma as you. That is until I went shooting with a client in what I considered heavy rain. He just went ahead popped his camera and started shooting, leaving me find shelter. later he explained what I had witnessed, the benefits of the Weather Seal. However, we must remember, these seals are ...


While the question has actually already been well answered, I just wanted to mention the term flange focal distance (also called flange to film distance), see e.g. Wikipedia. Basically, the camera manufacturers as Nikon and Canon have developed their first DSLR's using image sensors smaller than the illuminated film area of 135 film. As they did not want to ...


Your logic is sound. If your assumptions were right, then your conclusion would be right. Let me turn one of your questions around. You ask: Why does crop factor apply with APS-C-lenses, while it sounds like the image circle is compressed onto the APS-C-sensor (thus making a wider FOV)? In fact, the image circle isn't compressed, and does not make a ...


The image circle produced by a lens is independent of the focal length. It is the combination of the focal length and the sensor size that determine the effective FOV. For example, a 90mm lens designed for a view camera with film that is 4x5 inches in size will have a wide angle FOV on that camera. But take that same lens and mount it on a DSLR with an APS-C ...


You are misunderstanding a few things that are causing you confusion. The only difference between a lens designed for a full frame sensor and a lens designed for an APS-c sensor is that the APS-c lens collects less light since it is producing a smaller image circle. The light per surface area of the image circle is the same, but the circle is smaller. An ...


As others have wrote - it is difficult to make lenses that can focus at very different distances. Designer of the lenses have to choose possible distances because it may affect size, weight, complexity and finally cost of the lenses. In fact there are also lenses than can focus at very close distances but CAN'T at far distances. The example is this: Canon ...


This is kind of a hard head-to-head comparison, but basically, the EF-S 17-85 was an upgrade over the contemporaneous 18-55 kit lenses of its day (2004)--the non-USM, non-IS first version. The IS STM version of the 18-55 kit lens, however, is something like the eighth version of that lens, introduced in 2013, so it's a spanking new design, and probably ...

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