JPEG/TIFF/RAW query

[pressld2]

Originally Posted by bripriuk

I think most competitions will ask for your sequence of shots if you shoot jpg - you have to include those taken just before and after the entered shot. This way they can be reasonably certain that the shot is genuine.

Sorry but I don't really see how that helps. It's often just as easy to "illegally" modify a sequence of shots as it is to just do one. For example, it would be very simple to clone the beer can out of this image by Blackbrook Eye, rendering it inelligible for most competitions...



It would be just as easy to clone it out of a whole sequence. A little more time involved but that's all. Even easier than that is to just say "sorry, I only took the one shot of that subject". This isn't only a problem with jpegs; if you're a dishonest photographer it's not that hard to do it with raw files too. At the end of the day the judges have to use their best judgement but it really boils down to trust.

Originally Posted by bripriuk

Tiffs are not used in cameras

Depends on the camera. My Nikon D300 will shoot in TIFF and I expect the high end Canons will too. I use it whenever I need a high ISO because the in-camera high ISO noise reduction is much better than Lightroom's. But you're right, the file is three times the size of a raw file.

Dave P.

[bripriuk]

Dave
I didn't realise Nikons could save as Tiffs, I use Canons which don't.
It is actually impossible to modify a raw file as you can only save it as another format, not back as raw. However, I agree entirely that it will be impossible to stop someone who really wants to cheat. Back in the chemical days when I was printing wedding photos one of our clients asked for a print of the room shot of the reception - later one of his friends told us he had entered it in the local photo society comp as his own


Brian

[Paul mabbott]

Originally Posted by bripriuk

Paul

.BMP files were uncompressed bitmap files, ..........

They still are - it's the format I use when scanning pictures! Thanks for explaining why they're not used on cameras - although it still seems the best compromoise between RAW and JPG. Other things may have changed as well but I (and many others) used to have problems with incorporating the various TIF formats into other programmes ... ho hum!

[Wizmatt]

This is a little off topic. When you say resolution is that the dpi? Currently I leave the dpi on 350 when converting and saving files. At this resolution am I losing detail? Should I up the dpi to maintain detail?

Many thanks.

[paulthomas]

Originally Posted by Wizmatt

This is a little off topic. When you say resolution is that the dpi? Currently I leave the dpi on 350 when converting and saving files. At this resolution am I losing detail? Should I up the dpi to maintain detail?

Many thanks.

DPI is purely a a function of the physical printer. A camera's resolution is measured in pixels as are all the image formats that I've ever heard of (including your camera's own RAW format. With most image formats (such a JPEG or TIFF) there is no such concept as DPI. The image is X pixels by Y pixels and it the job of the printer device driver to map that to the physical DPI of the printer at print time.

There is considerable disagreement, even amongst printer manufacturers, how many DPI you need to produce a quality image. The oft-quoted figure of 300 is for printed text and is not really relevant to images as the eye views them differently. I've been fortunate over the years to have had on-line conversations about this with several photographers whose day job is is in printing and it seems that in practice around 150 to 160 DPI is sufficient.

[pressld2]

Completely agree with Paul's post. I have had three poster prints - 30" x 20" - made of 3000 x 2000 pixel images from my 6MP Nikon D70. So that's a print resolution of 100 dots per inch but the prints look fantastic (even if I do say it myself! ), better than similar size prints from a 35mm negative. In order to see any pixellation you have to be so close that you can no longer see the whole image, which is a bit pointless really. From a comfortable viewing distance of three or four feet they look superb.

Dave P.