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by Jakub

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visits member for 4 years, 10 months
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1d
comment Why don't people care any more about shutter speed accuracy?
@akram The problem was quite obvious, in aperture priority mode shots were coming out massively underexposed, but only at high shutter speeds like 1/1000s or 1/2000s, so I knew it couldn't be the metering. At very fast shutter speeds the rear curtain starts to close before the first curtain is fully open so any synchronisation issue between the curtains will be very obvious whilst not presenting much of a problem at slower shutter speeds where the rear curtain being 1mm ahead of where it should be would not change the exposure significantly.
Jul
22
comment Why does Sony say that a 35mm lens is “35mm equivalent when used with an APS-C camera?”
@shennan it seems you're not getting what happens when you put a lens on a smaller sensor - you get a smaller image, which has the same field of view as a longer focal length on a larger sensor. The lens is not "restricted" to an APS-C sensor, it's just if you put it on full frame you'll get darker corners. They could fix that but the lens would be heavier and more expensive. But even if they did that, it wouldn't change how it behaves on a smaller sensor, it would still give the same field of view as a 52.2mm lens would on full frame.
Jul
22
comment Why does Sony say that a 35mm lens is “35mm equivalent when used with an APS-C camera?”
@shennan No, interchangeable lenses are always sold by their actual focal length. This lens is a 35mm lens. The EFL when used with an APS-C sensor is 52.5mm
Jul
22
comment Why does Sony say that a 35mm lens is “35mm equivalent when used with an APS-C camera?”
@shennan Sony haven't fudged anything, the lens is called a 35mm lens because it's focal length is 35mm. It's 35mm when mounted on a full frame camera, it's 35mm when mounted on an APS-C camera, it's 35mm when it's in the box and not mounted on any camera at all... the focal length helps you work out the FOV, but it doesn't define the FOV by itself. Sony state the focal length that gives the same FOV on a full frame camera, to help people who understand the relationship between focal lengh and FOV on full frame cameras estimate the FOV of the lens on APS-C cameras.
Jul
22
comment Why does Sony say that a 35mm lens is “35mm equivalent when used with an APS-C camera?”
@shennan It's an APS-C lens because the image circle it illuminates is only big enough for an APS-C sensor. When mounted on a full frame camera the corners will be black.
Jul
22
comment Why does Sony say that a 35mm lens is “35mm equivalent when used with an APS-C camera?”
They name it as a 35mm lens because it is a 35mm lens, i.e. it brings parallel lines into focus 35mm behind the second principal plane. This is the definition of focal length, a property of the lens only, one that doesn't change when mounting the lens on different cameras. Focal length does not by itself define the field of view.
Jul
22
comment What are the anomalies in this picture of earth?
@NormLDude a simple paragraph would have sufficed under the pic that was posted on Flickr "May not be exactly as shown here" or "The quality of this image is 44% of the original" - the artifacts you're referring to are completely invisible until you perform a huge shadow boost, so why on Earth would they need to mention it? Should the same disclaimer be placed next to every JPEG image published anywhere in the web? Images NASA posts on Flickr are for PR purposes, not scientific analysis.
Jul
22
comment What are the anomalies in this picture of earth?
@NormLDude "There seems to be a lot of definition (3d)/depth to this 'anamoly'. The other circles surrounded by tiny circles are pretty interesting also." that is all completely explained by my answer - the 3D shapes come from the primitive building blocks which are all based on [co]sine waves.
Jul
21
comment Should I use a 24-105 or a 70-200 lens for photographing a high school marching band?
@PhilipKendall none of them. Sigma make a 120-300 f/2.8 though.
Jul
8
comment How can an electronic shutter reduce dynamic range?
Any increase to read noise will reduce dynamic range, I don't know the exact cause but it seems plausible that some aspect of the electronic shutter allows read noise to accumulate before or after exposure, or interferes in some way with one of the read noise reduction systems (correlated double sampling for example).
Jul
3
comment How is focus-breathing controlled in lens design?
@JDługosz It's not a calibration issue - most lenses achieve different focus distances by a combination of moving the lens and changing its focal length as this allows the lens to be more compact. The original Canon 100mm macro for example is reported to be only 70mm at it's closest focus.
Jul
2
comment Are there lenses that exhibit absolutely no focus breathing?
@feetwet it's more that case that cine lenses are specifically optimised for focus breathing whereas other lenses aren't, that doesn't mean there aren't SLR lenses with little focus breathing, though. I imagine it could be reduced to zero, but with everything in lens design it's a compromise so it's never going to be zero in a real lens.
Jul
2
comment What is the impact of the EU discussion on restricting freedom of panorama?
It's important to note that this is an EU directive not an EU regulation, that means states are free to interpret the content and implement it (or not) however they see fit.
Jul
2
comment Why do some cameras have a higher resolution sensor even though the max resolution is smaller?
@Muhatashim The edge pixels are permentantly masked, so there will be no difference when turning noise reduction on or off. The masked area is also probably larger than 16 pixels, I suspect the D3300 simply has a marginally larger masked area. 16 pixels on a 6,000 pixel wide image are fairly inconsequential anyway...
Jul
2
comment Why do some cameras have a higher resolution sensor even though the max resolution is smaller?
@DrMoishePippik No, DSLRs have dedicated metering sensors, metering via liveview uses regular pixels. Some mirrorless cameras (and a couple of Canon DSLRs) have phase detection AF pixels on the main imaging sensor but those are still used to produce the image. That article is about a very specific sensor design used only by Fuji.
Jun
18
comment What algorithm can I use to simulate bokeh?
Provided the operations are all additive you wont get the problem of dark areas spreading out. It's true you need a sharp mask to get sharp circles, but the major problem is that his bokeh operation is being applied to non-linear data.
Jun
18
comment Why did manufactures stop including DOF scales on lenses?
@akram The problem is DOF scales on lenses just aren't very accurate, they are based on the assumption of a very small output size (this is where the dependance on megapixels comes in, with a higher resolution sensor you are more likely no notice if something is out of focus), they also require you to estimate the distance to objects in the scene for them to make any sense. They were better than nothing in the days of film, but now it's easy to check if something is actually in focus using the LCD.
Jun
9
comment Is it possible to digitally capture a full 3D point of view?
@null You can make guesses, certainly, which is what that paper is doing, but that's not the same as having actual 3-d data. The correspondence between two images taken from different positions does contain 3D information.
Jun
9
comment What causes barrel distortion?
I don't have a time to do the full mathematical proof right now, but you do need a FOV of at least 180 degrees to see both vanishing points of two straight parallel lines.
Jun
8
comment Is it possible to digitally capture a full 3D point of view?
@null you can guess at depth, but that's it, there's no information there, from a technical standpoint. The best example of this is that it's impossible to tell the difference between a photograph of an object (that has depth), and a photograph of a photograph of an object (which has little-to-no depth). The reason you can't tell the difference is because there is insufficient information in the image.