Podcast #128: We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git. Listen now.
48

I've had to preserve whiteboard scribbles a few times. The problem is that you usually can't control the lighting and it's rarely good. The technique I've converged on is to take two pictures. With the camera on a tripod, take the first picture of the board as is. Then erase the board and take the second picture with exactly the same settings. Now ...


33

You're right that the angle of view of the iPhone camera is a little bit wider than a 35mm lens on a full-frame film camera. Up until this point, you're not really confused. But the part after that, about the small room and zoom and distance — definitely confused. :) "Zoom" means the ability to change the field of view — it isn't magnification. See What is ...


23

Your friend is right that it is actually always a 24mm lens — that is a property of the optics and never changes. But, he's wrong in saying that the crop factor does not apply. That's a property of the sensor size of the camera. From a practical point of view, zoom — changing focal length — and cropping are interchangeable. So, using a camera with a smaller ...


19

It depends on what you're asking exactly, if you're asking what focal length provides the same magnification as the naked eye (as in you hold your hand out infront of the camera and look through the viewfinder, your hand appears the same size as it would without the camera), then the answer depends on sensor size and viewfinder magnification, but the answer ...


16

That depends on the sensor size of the camera. "A lens is considered to be a "normal lens", in terms of its angle of view on a camera, when its focal length is approximately equal to the diagonal dimension of the film format or image sensor format.[4] The resulting diagonal angle of view of about 53 degrees is often said to approximate the angle ...


15

That difference is because the angle of view of the APS-C sensor is smaller than the 35mm Full frame sensor. Basically the change of focal length is only considered as a change of angle of view. APS-C sensor has a crop factor of 1.6 of the full frame sensor. ie Anything viewed with the APS-C sensor will be cropped 1.6 times the Full frame sensor.Hence 300x1....


15

You have already chosen your answer but I'd thought I would elaborate a little. Focal Length: Yes, it stays the same! The age of the lens doesn't matter regarding focal length. As long as there is some way of fitting any lens onto a body (generally a bigger format lens on a smaller format body), whether by an adaptor or by physically changing the mount, ...


15

Provided you keep focus distance, ISO, aperture & shutter speed the same, and you zoom your 18-55mm lens to exactly the same focal length as the 50mm prime (which wont be exactly 50mm) then the images will very extremely similar when viewed as a whole. On closer inspection you will see differences in the level of distortion, sharpness, contrast and ...


15

I don't understand why anyone would buy it Optical quality, build quality, and overall durability. The EF 17-40mm f/4L USM is an "L series" lens -- essentially professional grade, while the EF-S 18-55mm f/3.5-5.6 is a consumer grade "kit" lens. L lenses are made with better materials, better designs, and more features. They're weather sealed to keep out ...


14

Whether a lens is an EF or an EF-S lens, the actual focal length is always used. There are certain technical reasons why this is so, but the simplest is that a lens' focal length is defined as the distance from the film plane needed when the lens is focused at infinity to cast point light sources as a single point on the film plane. This doesn't change with ...


13

When you look through a viewfinder, a lens at around 50mm focal length will show objects at the same size as when you look at something with your eyes. You could test this by looking through the viewfinder with one eye, and looking next to it with the other eye. When you close one of your eyes, you will notice that your sight does not change, regarding the ...


13

They're measuring the first on a crop-sensor camera and the second on a full-frame; specifically for a Canon APS-C sensor, 15mm x 1.6 = 24mm. Canon does this in general when referring to EF-S vs. EF lenses; see for example How can a 24-70mm and a 10-22mm both be "wide angle" lenses?, which has the same effective answer. The relationship between ...


13

The principle of physics behind this behaviour is nothing more than the thin lens formula: 1/o + 1/i = 1/f Where o is the object distance (distance from lens to subject), i is the image distance (distance from lens to sensor), and f is the focal length. For a very large object distance (approaching infinity) the 1/o term drops to zero, hence: 1/i = 1/f i ...


13

Assuming both lenses are being used on the same size sensor, the area in the frame with a 600mm lens should be one quarter the area in the frame with a 300mm lens. The linear dimensions should change by a factor of two, the areal dimensions should change by a factor of the square of two, which is four. If you are not seeing the same object shot from the ...


13

Answer with an image : the guy on the left represents your (vertical) field of view and its image on the sensor is inverted on the right (in other terms, the guy fills your entire image). As you can see in this illustration, the rays of light going through the center of your lens aren't concerned by your aperture settings, they are still getting in, no ...


12

Google Sketchup 8 (a free 3D modelling software) enables users (being a Google product) to "legally" add Google maps imagery and terrain to 3D models. You can then use the protractor tool to measure and draw your line of sight and an angle of view. In fact you can easily draw a 3D cone as well that will enable you to analyze the angle of view in 3D. In ...


12

The calculators you posted are for fairly standard, rectilinear lenses. This means you can use the Pinhole camera model to calculate the information. This graphic fairly well shows what is going on: On the horizontal axis you see f. This is the focal length of the lens. Then, the arrow labeled Y1 is the image plane (where the sensor sits). If the sensor ...


11

The 50mm 1.8G is a great lens. But there isn't going to be a huge difference in image quality using any of the 35mm or 50mm primes. I don't think anyone but you can really answer which one is more suitable for you. There may be some situations where you can only get so close, or so far, to frame your shot, and one focal length or the other might limit you ...


11

There's really no such thing as a 'theoretically perfect' rectilinear lens with a perfectly flat field of focus and no geometric distortion. Even a lens that perfectly matches its blueprint would not demonstrate such perfection. A theoretical thin lens demonstrates field curvature as well as several other aberrations. Various corrective elements used to ...


10

I regularly take photos of whiteboards sized 3' x 4' or larger with my cell phone camera to record meeting notes, and it produces passable results. The D90 should absolutely kick butt on this. The two factors you want to avoid are glare and motion blur. As Guffa mentioned, you want to avoid glare from ambient (room) lighting, so get into a position as ...


10

Your intuition is right. To validate it, we can dig into basic high-school geometry. Although a camera lens is actually a complex lens made from many elements, conceptually and mathematically for most practical purposes, this reduces to an ideal, where you can imagine a pinhole exactly a distance from the sensor equal to the focal length. Light might fall ...


9

The viewing distance of an image is based on two factors; first is the diagonal image size and second are the pixels per inch required at that distance to give a sharp image. Firstly the rough rule of thumb is that the viewing distance should be 1.5 to 2 times the diagonal length. This will give you an optimal viewing distance for the overall printed size ...


9

It depends on the lens design, a wide angle retrofocus lens is mainly limited by the front element size, the lens barrel places a hard limit on the range of angles that can see the entrance pupil. As an example of this mounting a filter on an ultrwide can reduce the size of the image circle. This is why separate designs exist for APS-c DSLRs, but mostly for ...


8

On some lenses the image circle does indeed get bigger as you zoom. I know from experience the Canon EF-S 10-22 f/3.5-4.5 does this. At 12mm the image circle is big enough for a 1.3x crop APS-H sized sensor and by 15mm it is big enough for a full frame 35mm sensor. However lenses such as the EF-S 17-55 f/2.8 vignette at all focal lengths on full frame. I ...


8

The actual focal length is 4mm. The 35mm equivalent tells you what focal length you'd need to use with a 35mm film/sensor to achieve the same result, but it doesn't have much optical sense. Assuming the sensor width is 4.54mm: FOV = 2*atan(.5*4.54mm/4mm) FOV ~ 1.03235913 rad FOV ~ 59.1498211 deg That is roughly 40% of a human's field of view.


7

The adapter bridges the gap in flange distance (distance between mount and sensor/film) between the NEX native E-mount (18mm), and the MD/SR mount (43.5mm). Therefore, the focal length of the MD lens isn't affected, it's still at its native flange distance from the sensor. If you were to adapt an MD lens to a mount with longer flange distance (i.e. canon ...


7

Assuming the same scene and focal lengths chosen to match field of view: Perspective will be the same, as it is a function of subject distance. Exposure will be the same for he same f-stop. Depth of field will be different for the same f-stop, as it is a function of absolute aperture size, 50/2.8 is a bigger quantity than 35/2.8, so the 50mm lens will have ...


7

To properly relate scale in a photograph, you need either the proper perspective or something of known size that can be compared to the rest of the scene. You have pretty decent perspective, however there is nothing near to the camera...everything is at greater distance. Additionally, there is nothing of well-known size to relate the size of the building to. ...


7

In short, yes, it is actually different, but only because the angle of view is by definition measured to the edge of your view — which is the edge of the sensor, which is (again by definition) different on APS-C. Your statement I think that the angle of view, depth of field, and compression are the same as on an FX/Full frame but we are seeing only ...


7

The formula you're asking for is x = (fl * d) / s Where s is the diagonal size of the image sensor — 43.3mm for a full frame sensor. However, for a 12" x 8" landscape print from a 24mm lens, your viewing distance works out to be about 8 inches — not exactly comfortable — and that's if  your eyes can actually focus properly. A picture being flat ...


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