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Controlling compression with (Nikon) digital cameras.
Dear experts,
I'm very familiar with 35mm photography, but new to digital. One thing I do know about photo editing is how you can control the compression on the the jpeg. The more compression, the more loss, and vice versa. Yesterday, I bought a Nikon 3200 and a one gig memory card. The manual says that the compression is set indirectly in the image mode. When I set it to the highest 3 megapixel setting, it uses about a 1:4 compression ratio. The next 3M setting uses a 1:8 compression ratio. I set it to the highest quality image and took a few pictures with the camera and uploaded them. They all seemed to have their jpeg compression set to 50%. In Windows, the 773 kb jpeg file, when saved again as ..jpg at 100%: 1305 kb ..bmp 9217 kb. Are there point and shoot cameras where you can control the amount of jpg compression? Which cameras allow you to do this? How about on the D70? I've also heard of Raw. Nikon stores these as .NEF. Is this the same as a .BMP file on Windows? Thanks |
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commented courteously ...
Yesterday, I bought a Nikon 3200 and a one gig memory card. The manual says that the compression is set indirectly in the image mode. When I set it to the highest 3 megapixel setting, it uses about a 1:4 compression ratio. The next 3M setting uses a 1:8 compression ratio. I have a 5700, which was $700 retail. To give me an idea what you have, is your 3200 a $400 camera or a $100 camera? If it is like my wife's $150 Kodak, she can only change resolution, and cannot control JPEG compression (which Kodak has set way too high, so the pictures have artifacts despite their 3 mega pixel size!) I set it to the highest quality image and took a few pictures with the camera and uploaded them. They all seemed to have their jpeg compression set to 50%. JPEG compression is not a percentage. Rather, it is an arbitrary 1-100 scale. Are you saying that your images look like a JPEG 50? If so, the quality must suck on quite a few of them. I see lots of artifacts on my wife's Kodak's and I'd judge the compression at around 25-30. Are there point and shoot cameras where you can control the amount of jpg compression? Which cameras allow you to do this? How about on the D70? Little P & S cameras do not have any JPEG controls generally, ala my wife's Kodak. I'm not sure where the price point is where you see "basic", "normal", and "fine" (none have an actual compression number that I know of) but I'd imagine its around $300-400. Nikon's "better" cameras have all sorts of controls over the image. The D70 is a fairly high-priced camera and may well be overkill for you. If you like Nikon, look around the web for a 5700. They've been out-of-production for six months but stores still have them, and Nikon pops for a $150 mail rebate. It's a very fine camera, I can personally attest to that (except for flash). I've also heard of Raw. Nikon stores these as .NEF. Is this the same as a .BMP file on Windows? NEF is Nikon's proprietary RAW. It is in *no* way a Windoze BMP, which is nothing more than an uncompressed bitmap file (hence its name)! RAW/NEF give you total control over the picture parameters even after you've taken the shot. I don't use NEF with my 5700 because I don't think I need it, but lots of people think that NEF/RAW is essential to their work. There's plenty of folks on this NG that are much knowledgeable than I am about this stuff, so you'd help everyone lock onto what you need to do if you give some details on price and purpose. Good luck, and Happy New Year! -- ATM, aka Jerry Rivers |
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There is only one camera that I'm aware of (Canon 1ds MII $8000) where you can specify the actual compression ratio of a jpg image. In camera, rather, you set the image size, and then the type (JPG, TIFF, RAW). This is how even most high end cameras (like my D1x) works. The jpg image is saved at a preset compression based on the output size specified. If you want to LOWER that, then use software. The ratio that you are attempting to determine is NOT something you can mathmatically figure with a simple calculation as jpg size is based largely on WHAT is in an image. A lot of Blue sky = smaller image. A lot of varied colored detail = bigger image. One can NOT assume a compression ratio based on the image size alone. Shooting RAW has advantages over most other formats. RAW is a 16 bit format (actually 12 for most) vs. the 8 bit jpg and TIFF formats. Some of the newer DLSR's have a 16bit TIFF option. The bottom line is that if your biggest concern in shooting a PnS is the compression ratio of jpg, than you are likely not going to have to worry much. There are MANY things that can impact the ability to shoot high quality images with a PnS digital (as good as they are). So to worry about jpg compression is rather pointless. Shoot with the highest res possible, and if you are unhappy with your images, then you will want a better tool. Ron |
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There is only one camera that I'm aware of (Canon 1ds MII $8000) where you can specify the actual compression ratio of a jpg image. In camera, rather, you set the image size, and then the type (JPG, TIFF, RAW). This is how even most high end cameras (like my D1x) works. The jpg image is saved at a preset compression based on the output size specified. If you want to LOWER that, then use software. The ratio that you are attempting to determine is NOT something you can mathmatically figure with a simple calculation as jpg size is based largely on WHAT is in an image. A lot of Blue sky = smaller image. A lot of varied colored detail = bigger image. One can NOT assume a compression ratio based on the image size alone. Shooting RAW has advantages over most other formats. RAW is a 16 bit format (actually 12 for most) vs. the 8 bit jpg and TIFF formats. Some of the newer DLSR's have a 16bit TIFF option. The bottom line is that if your biggest concern in shooting a PnS is the compression ratio of jpg, than you are likely not going to have to worry much. There are MANY things that can impact the ability to shoot high quality images with a PnS digital (as good as they are). So to worry about jpg compression is rather pointless. Shoot with the highest res possible, and if you are unhappy with your images, then you will want a better tool. Ron |
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