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Photo Forum / Digital Photography / DSLR Cameras / March 2005pixel density
How does pixel density influence the resolution at super telephoto? For example: Is it better to buy a: 1. Nikon 8800 with a teleconverter 2.Olympus e300 2x crop factor 3.Canon 350d 1.5 or 1.6 crop factor 4.Panasonic FZ20 with a 2.8/420mm x teleconverter? 5.7mpix consumer camera disassembled and lens replaced with a 35mm slr lens Lens options: 1.Opteka/Exakta/Samiyang/Vivitar/whatever 650-1300mm f/8-f16 lens (1300mm f/8 EFL Olympus) (teleconverter???) 250 Eur 2.100-400 f/5.6 with 1.4x teleconverter 500 Eur 3.80-200 f/2.8 Tamron or Tokina with a 3x Kenko teleconverter 600 Eur + 250 Eur 4.600 mm f/8 mirror 5.50-500mm f/6.3 Sigma with 2x and 1.4x teleconverters 6. A diy project of makeing the lens myself from components (found a front lens 17cm diameter) 7. A telescope with an adapter 6 inch 1200 f/8 refractor 500 Eur + adapter My goal is to get an image similar to the one from 20x50 binoculars or better. 50mm lens is normal 1x, then 1000mm is 20x normal??? Thanks in advance. | How does pixel density influence the resolution at super telephoto? | For example: Is it better to buy a: [quoted text clipped - 22 lines] | | Thanks in advance. It seems to me that "pixel density" is a digital construct so the lenses don't play in this, the MP resolution of the dSLR will and how the digital representation is rendered on the computer.  SignatureDave > It seems to me that "pixel density" is a digital construct so the lenses don't play in this, > the MP resolution of the dSLR will and how the digital representation is rendered on the > computer. Ok, how can you compare a prosumer Nikon 8800 with a dslr if no lenses are mentioned? Price range is also important. I dont have 7000 euros for a sigma 800 f/5.6 :((( Zoom with a 2-3X teleconverter is going to look really bad. With smaller sensors, the optical quality of the lens is MUCH more critical. Something that was just so-so on 35mm, will probably look like crap on a 1.6-2.0X factor sensor camera. SignatureStacey Does sigma 50-500mm f/6.3 with 2x tc look like crap? Where is the limit where "crap" starts to happen? > Does sigma 50-500mm f/6.3 with 2x tc look like crap? Well it's a SUPER wide range zoom with a 2X converter, probably not a good one so yea, I bet it will be pretty bad. > Where is the limit where "crap" starts to happen? ?? If you want decent quality with a TC, especially a cheap one, stick with prime lenses. I had OK luck years ago with a 400mm tokina with a 2X converter, wasn't great but was usable. SignatureStacey >?? If you want decent quality with a TC, especially a cheap one, stick with >prime lenses. I had OK luck years ago with a 400mm tokina with a 2X >converter, wasn't great but was usable. You have to realize that a 2x will use up a lot of light. You need to halve the exposure time, for the same image stability, and you need 2 stops more to get the same exposure. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > You have to realize that a 2x will use up a lot of light. You need to > halve the exposure time, for the same image stability, and you need 2 > stops more to get the same exposure. One stop. KeS >> You have to realize that a 2x will use up a lot of light. You need to >> halve the exposure time, for the same image stability, and you need 2 >> stops more to get the same exposure. > >One stop. Nope - two stops. A 1.4x costs you one stop. In message <Pine.OSX.4.58.0503041556170.15858@onorysvfu.chefhrq-jvgu.arg>, >> You have to realize that a 2x will use up a lot of light. You need to >> halve the exposure time, for the same image stability, and you need 2 >> stops more to get the same exposure. > >One stop. A 2x doubles the width and the height of the focused image center, increasing the area 4x, which is a 2-stop loss of light. You may also need to stop down the lens beyond this to maintain local contrast; depending on the conditions, a 2x will generally cost you anywhere from 2 to 5 stops of light, if used optimally. I generally only do it when I am shooting in direct sunlight, or under a light haze. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >Does sigma 50-500mm f/6.3 with 2x tc look like crap? >Where is the limit where "crap" starts to happen? I had one of these for two weeks before returning it. It was not TC-able at all, IMO. At 500mm, the lens was already more limiting than the sensor. All 2x500mm shots were very soft, regardless of stopping down or using extreme shutter speeds. I would consider this lens a good 50-375mm zoom, with some extra empty magnification up to "500mm". I really liked the ability to do scenics and birds with the same lens, but it is *heavy*. I'm much happier with the Canon 100-400; it's 2/3 the weight, has IS, and can use a 1.4x or even a 2x if stopped down a bit in very bright light (no AF, though). Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >Zoom with a 2-3X teleconverter is going to look really bad. With smaller >sensors, the optical quality of the lens is MUCH more critical. Something >that was just so-so on 35mm, will probably look like crap on a 1.6-2.0X >factor sensor camera. That depends on the lens. Some can just barely deliver what the sensor can resolve, some fail to meet that, and others can be magnified 2 to 3 times, and still have pixel-to-pixel contrast that is respectable. The spacing of the pixels is more relevant than the number. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > How does pixel density influence the resolution at super telephoto? > For example: Is it better to buy a: [quoted text clipped - 22 lines] > > Thanks in advance. I'd agree that 1000mm is about 20x for a normal 35mm film format but the issue is more about field of view. What is the field of view for the 20x50 binoculars you are trying to emulate? I consider a normal lens to be 1.4x the longest dimension of the image area. For 35mm that is 36 x 1.4 = 50.4mm as normal. For 4/3 it would be 25.2mm. A 500mm lens on a 4/3 sensor is about 20x but the field of view may not be similar enough to a wide angle binocular for you needs. Experiment or research... -Guy > How does pixel density influence the resolution at super telephoto? > For example: Is it better to buy a: [quoted text clipped - 20 lines] > better. > 50mm lens is normal 1x, then 1000mm is 20x normal??? Auto focus speed or manual focus feasibility are also important. Canon 300D might be affordable to you. For AF, you need f/5.6 or better. Affordable good lenses include 400/5.6, 300/4, and 200/2.8. All 3 has the same physical lens openning of about 70mm. So with tele converters, they can be effectively the same as 400/5.6, (300/4 + 1.4x or 200/2.8 + 2x), to keep AF. With the 1.6x cropping of 300D, it is equivalent to 640/5.6. If 43mm is 1x (the diagonal of the 36x24 frame), 640mm is about 15x, close to your 20x binocular. If you want more reach than the 15x, you can stack on more TC, 400/5.6 + 1.4x, 300/4 + 2x, or 200/2.8 + 3x (2x + 1.4x). The result will be smaller than f/5.6 so you would lose AF on 300D. You can block some lens electric contacts to fool the camera about TC to retain AF, or use some 3rd party TC that does not transfer those contacts. If MF is OK for you, then 600/8 mirror is OK. |
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