Alley in Pisa, Italy

by Lars Kotthoff

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bio website mattgrum.com
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visits member for 3 years, 10 months
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4h
comment Why are Micro Four Thirds lenses so expensive compared to Canon?
@mattdm that's a good point, looks like all mirrorless systems are out of the running for cheap 50s, in order to offer compactness you need a more complex design which adds to the cost (or release a double gauss design with a big tube stuck on the back!)
4h
comment Why are Micro Four Thirds lenses so expensive compared to Canon?
@AdamDavis there is no sweet spot due to the short flange distance and requirement that all lenses be [object space] telecentric
7h
comment What effects do different flash diffuser shapes have?
That image may be rendered, but not all Apple product photos are: theverge.com/2013/5/8/4311868/…
7h
comment Why use higher ISO when using a tripod and the object is static?
This is why DOF calculators are completely misleading. Depth of field depends on the distance at which you view the print/image. There's simply no way for you to know how large the photographer may have printed the image or where he intends it to be viewed from. The figures you quote assume a circle of confusion of 0.03mm, which is about five times the size of a 5D mkIII pixel! If you want to avoid a 5 pixel blur then f/4 wont cut it. In fact using the 5D pixel size as the CoC, according to the calculator to get everything from 147 feet to infinity in focus you need to stop down to... f/20!
1d
comment Lighter section in photograph
It's called a rolling shutter artifact.
2d
comment Why do I meter under the chin with a lightmeter?
you want to meter the darkest parts of the image to ensure you have sufficient signal in the shadows to resolve the image well this still implies the lightmeter is measuring the darkness of the shadows which is the exactly the misconception that prompted the question in the first place, and is out of line with common practice. If you wanted to ensure the shadows were within a certain range you'd just point the lightmeter dome toward the fill light/reflector. Since all of the subject skin will reflect the same amount of light you only ever need to record the incident levels.
2d
comment How do disposable cameras work without exposure and focus control?
possible duplicate of What is the shutter speed, aperture, and focal length of the Kodak Funsaver disposable camera?
Jul
22
comment Why do I meter under the chin with a lightmeter?
The correct way to fix problems such as shadow noise in portraiture is through extra lights / reflectors, not by ETTR (which is more for landscapes, where you can't fill light a whole mountainside). The best way to meter for portraits is to measure the incident light, not the light reflected from the subject. If only one reading was taken it was almost certainly an incident reading. I've never heard of anyone taking a single reflected reading from a shadow area in order to completely determine the exposure for a portrait!
Jul
18
comment How can I get perfect sharpness when shooting still art?
@user28116 Firstly "don't overexpose" is shorthand for don't push the exposure so far you run into problems of clipping and nonlinearity (in any case avoiding nonlinearity in no way requires underexposure by 2 stops!). If you start with the camera's 18% metering reading and go down two stops from there you really are going to lose quality. Finally I will "ride" that answer until the laws of physics and mathematics change to render it incorrect :)
Jul
18
comment How can I get perfect sharpness when shooting still art?
@user28116 Digital sensors are very linear with respect to incoming light vs. recorded value (unlike film) so provided you don't overexpose you'll capture the full range of details no matter where you place the exposure. Reducing the exposure, on the other hand, will absolutely increase noise in all circumstances.
Jul
17
comment How can I get perfect sharpness when shooting still art?
Likewise, why less than 1 second exposure and ISO200, can you provide any more details?
Jul
17
comment How can I get perfect sharpness when shooting still art?
I'm not sure what underexposing is going to do to help detail (if anything it's going to increase noise) unless you're getting problems with mirror slap at certain shutter speeds.
Jul
15
comment Raw is larger and softer than JPG
@clabacchio I think the real reason is, as stated in the dcraw documentation: "Any algorithm that combines each pixel with its neighbors is going to have problems near the edges. C code is cheap, so dcraw applies a different algorithm to edge pixels. Hardware logic is expensive, so cameras crop off the edge pixels after processing"
Jul
15
comment Raw is larger and softer than JPG
@clabacchio The JPEG standard allows for incomplete blocks along the bottom and/or right edges of the image, meaning image dimensions do not have to be multiples of 8. Additionally I know of no image editor that crops images to a multiple of 8 before saving. RAW converters may aim for multiples of 8 in order to produce JPEG images which can be rotated without re-encoding (a desirable property of camera generated JPEGs).
Jul
15
comment Dark zone appearing on pictures when using an external flash
Basically what @JamesSnell said. It's worth noting that with the Canon 430EX (and similar speedlights) reducing the flash power also reduces the flash duration, making it better at freezing motion (but make sure you're still able to overpower the ambient light or you'll get blur).
Jul
15
comment Dark zone appearing on pictures when using an external flash
It is a duplicate - the sync speed of the 6D is 1/180s, shoot faster than this and you'll see the shutter curtains. Case closed.
Jul
9
comment Foveon x3 sensor
@KendallHelmstetterGelner this isn't a discussion forum, so that's all for now I'm going to update my answer when I get a chance and provide sources for everything, I'm not making all this up - I very nearly bought a DP2M, and did a lot of research.
Jul
9
comment Foveon x3 sensor
@KendallHelmstetterGelner I meant a yellow object in an image contains red and green. Also you missed the point entirely, red and green don't measure the same spatial location, but when the red and green response increase together then you can use the green values to reliably estimate what the missing red values are and vice versa. So you get 33.75MP of red and green data, and you only need to "guess" 1 in every 4 pixels where there is a blue sensor which doesn't record useful information for yellow objects. That's a lot more than the 15MP of red and green you get from the X3.
Jul
8
comment Is there an automated way to create composites from multiple images of a moving object?
I think you might have it the wrong way round, the question was asking about a fixed camera and moving object, the object should appear many times in the final image in different positions. Pick up any snowboarding magazine for an example of this effect!
Jul
8
comment Foveon x3 sensor
@KendallHelmstetterGelner With 45MP total, in the worst case (e.g. only red light) you get 11.25MP out of the Bayer and 15MP out of the X3. In the best case (e.g. a monochrome scene) you still get 15MP out of the X3 but get 45MP out of the Bayer! Yes most scenes have colour elements. A yellow object contains red & green light, when the brightness of yellow changes, red & green change by the same ammount, and demosaicing can fill in the missing red values using green of which there are 22.5MP! So it's really a case of fixed 15MP, or between 11.25MP and 45MP, averaging somewhere in the middle.