A few beginner & semi-techy questions, if you have the time...

Started Jul 2, 2014 | Discussions thread
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CreeDo Senior Member • Posts: 1,619
A few beginner & semi-techy questions, if you have the time...

You don't have to answer them all, but if you can answer any one of them with confidence and explain it in a simple clear way, I'd appreciate it. I can't seem to find great answers when I try to google this stuff.

1. I don't get how crop sensor = longer zoom / telephoto ability. What's happening optically that allows an APS-C to 'reach' further than a full frame camera?

Is that really what's happening or does it just seem that way because the image on the APS-C has stuff around the edges cropped away so it looks like you're focused on a narrower area of the scene?

In other words, if I have the same lens on an APS-C and a full frame, will the APS-C somehow pick out detail at long distances that the full frame can't? If so, how is that possible? The quality of the optics didn't change so why can the lens pick out those details on one camera but somehow not 'see' them on the other?

2. What's happening when a lens can't "use" the full number of megapixels that a camera offers? I mean, if you have a 36 megapixel camera, and the file format is 7360 x 4912, isn't every single pixel getting filled with a colored dot even if it's not all perfectly sharp? No matter what lens you use, you end up with a file that's 7360 x 4912 (36,152,320 pixels) every time. When some review / benchmark site says the lens can only use, say, 28 megapixels out of the 36... how did they arrive at that number, and how is the camera filling in the gap between 28 megapixels and 36 to product that giant 7360 x 4912 jpeg?

3. Does stopping down more than, I dunno, f-16 have any use? I get two different answers even from people who are making a living with photography. I understand it affects depth of field. One guy says "going above f-whatever is not going to sharpen the photo, it's going to make it blurrier, due to diffraction." ...I can see in tests that this is correct. I feel like none of my lenses gain anything by going above f11, and often the shots look less sharp past that point.

But another guy says "jack up the f-number as high as it will go if you want maximum sharpness on your shot, light permitting." Is that true only for certain lenses? Or maybe if you want sharpness on a shot covering a huge focal distance, like trying to get the entire Grand Canyon sharp? Maybe it applies to super telephoto lenses but not to typical x - 300mm ranges?

4. Do these MTF and DxOmark tests accurately portray how sharp one lens is vs. another to the human eye? Or are there intangibles they're missing? I don't mean intangibles like portability, or 'warmth' of the colors, etc. Strictly in terms of resolving power. Obviously the human eye can tell when something is sharp or not but how do they scientifically determine that?

5. Do lens prices somewhat reflect what they actually cost to produce? Or are the manufacturers just gouging when they ask for like $10,000+ for a lens, and assume some buyers will just pay anything for the top of the line? It seems like the parts / materials can't be all that much. Glass and steel and plastic. Are these special coatings expensive? The labor is done by (presumably expensive) machines. I guess the expertise (well-paid lens engineers) cost a lot?

6. What is the big challenge in getting low f-numbers in lenses, that makes them so expensive? I mean, is the lens glass getting ground a certain way, or to more exacting standards? More (or more complex) elements? Are low f-number lenses actually tougher and costlier to manufacture than the cheaper high f-number counterparts? Or do they just cost more because they are more useful / desirable?

7. Any advantage at all to using my in-camera color/sharpening/etc. options, vs. just photoshopping the image afterwards? Besides saving time? Sharpening in particular is interesting. Is this just postprocessing done by the camera, or does it actually capture the raw image differently if you jack up the camera's internal sharpness setting? Is it just 'fake' sharpness like photoshop's unsharp mask, or can I actually see details there would otherwise be missing if I didn't touch the setting?

On the same theme, any advantage at all to shooting in black and white when I can just use adobe's raw editor to make it monochrome and tweak individual colors and contrast etc etc?

8. How does optical stabilization work? Why can't they put it in every lens?

 CreeDo's gear list:CreeDo's gear list
Canon EOS 7D Mark II Canon EF-S 60mm f/2.8 Macro USM Canon EF 70-200mm f/2.8L IS II USM Rokinon 14mm F2.8 IF ED MC Sigma 18-35mm F1.8 DC HSM Art +3 more
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