Red and Blue

by Gordon

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

99,589 reputation
4210363
bio website mattgrum.com
location
age
visits member for 4 years, 8 months
seen 5 hours ago

Jan
27
comment Do DSLRs play games with ISO when used with fast lenses?
@jrista "They state many times that they normalize all images to an 8mp image 'printed' on an 8x12 (20cm x 30cm) image at 300dpi. They also state that it is "exactly" 8mp, however an 8x12@300dpi print is 8.6mp (3600x2400)" you're misrepresenting what they say here, the exact quote from DXO is: "we chose a reference resolution equal to 8 Megapixels, which is a bit less than a 12" x 8" print with a 300dpi printer" you are correct that 12x8 300dpi is 8.6MP, but note the use of the words "a bit less"!
Jan
27
comment Do DSLRs play games with ISO when used with fast lenses?
@jrista I am not sure where DXO states that you need to subtract 3 stops to get a real-world value for DR they don't, I'm saying that your figures seem to differ by three stops. As everyone has their own definition of what "usable" DR is. But once you know how your own sense of DR differs you can use the DXO-mark figures to compare cameras and adjust your expectation of "real world" DR accordingly.
Jan
27
comment Do DSLRs play games with ISO when used with fast lenses?
@jrista "DXO does not clearly state what that "21.6 bits of information" is" they do actually: As with tonal range, color sensitivity is a number with no unit, so instead we consider Log2 CS, which represents the number of bits necessary to encode all distinguishable color values. They also define distinct colours as ones where the difference between the colours exceeds the colour noise. Here's the relevant page: dxomark.com/index.php/en/Learn-more/DxOMark-database/…
Jan
27
comment Do DSLRs play games with ISO when used with fast lenses?
@jetxee there's pages of info about what the measurements mean and how they are taken, it's accessible from the "learn more" link right on the main page. See dxomark.com/index.php/en/Learn-more/DxOMark-database/… and dxomark.com/index.php/en/Learn-more/DxOMark-database/… and dxomark.com/index.php/en/Learn-more/DxOMark-database/… and dxomark.com/index.php/en/Learn-more/DxOMark-database/… + dxomark.com/index.php/en/Learn-more/Glossary for starters
Jan
27
revised What do I need to get photos with a unifom black background (not with post)?
added 855 characters in body
Jan
27
revised What do I need to get photos with a unifom black background (not with post)?
added 426 characters in body
Jan
27
revised What do I need to get photos with a unifom black background (not with post)?
deleted 36 characters in body
Jan
27
comment What do I need to get photos with a unifom black background (not with post)?
@tom thanks, I meant to type "9" but missed the key by one!
Jan
27
revised What do I need to get photos with a unifom black background (not with post)?
added 516 characters in body
Jan
27
revised What do I need to get photos with a unifom black background (not with post)?
added 593 characters in body
Jan
27
answered What do I need to get photos with a unifom black background (not with post)?
Jan
27
comment Should I switch off image stabilization when photographing my 2 year old?
The problem is your shutter speed of 1/50 isn't really fast. It's just about fast enough to avoid camera shake if you're still and composing your shots, but for tracking a moving subject like a child you should probably be at 1/200 or 1/320
Jan
27
comment Tips & advice for photographing store/shop interiors
I would advocate a tripod instead of a fast lens for this sort of project. "Wide" and "fast" don't really go together unless you invite their cousin "really expensive"... a slow wideangle and longer exposure should do the job more cheaply, I can't think why you'd want to limit depth of field in a wideangle shot.
Jan
27
comment When comparing sensor dynamic range, what are those numbers based on?
@jrista as you've stated you can increase the apparent DR by exposing to the right (btw if the lighting allows you to push the histogram further to the right that indicates the scene has lower DR, not the camera has more) which is why it can be useful to know the limits of detail that can be recorded so you know what you can pull out of the shadows in a pinch. The K5 JPEGs may have the similar DR as the 450D, but raw on the K5 lets you recover more detail in post, upping the DR of your final image. This info is revealed by DXO but might be missed by a subjective assessment of camera output.
Jan
27
comment When comparing sensor dynamic range, what are those numbers based on?
labnut took the words out of my mouth, DXO-mark is about comparing sensors, not about saying "this sensor can image 14 EV so I can take it to a scene with what I consider to be 14 stops range and just snap away" I think measurable DR and subjective useable DR (after PP, see my next comment) probably correlate well so you can use the figures and adjust in your head if you prefer.
Jan
26
revised When comparing sensor dynamic range, what are those numbers based on?
added missing "s" from title
Jan
26
comment When comparing sensor dynamic range, what are those numbers based on?
The whole "big sensor -> more dynamic range" thing is a bit of a myth. Small sensors with good electronics (low noise floor) can exhibit large dynamic range, look at the Pentax K5 for example. It's a hangover from film, when noise was determined by the emulsion so using the same film in a larger format would convey an advantage due to the extra light captured.
Jan
26
revised When comparing sensor dynamic range, what are those numbers based on?
added 779 characters in body
Jan
26
revised When comparing sensor dynamic range, what are those numbers based on?
added 586 characters in body
Jan
26
comment When comparing sensor dynamic range, what are those numbers based on?
@Shizam I've updated my answer, basically I think the 5-6 EV result is based on a qualitative assessment by photographers rather than a measurement by software.