I will be grateful to know why lenses of same specifications give different picture resolution. Is it the abberation, the ghosting, the flare etc.??

Thank you

According to my sources, there is a “system magnification”–perhaps not unlike the digital zoom that takes place with crop cameras as in the case of the following Nikon D300:

“The image produced on the small-sensor DX (D300) will be enlarged more to produce output (print or screen) that matches the output of a longer focal length lens on a full-frame… camera. This ‘enlargement’ is a internal system magnification not a true lens magnification but the result is somewhat the same.”

[source: http://meanderingpassage.com/2008/09/08/photography-magnificationcrop-factor-d700-and-d300/

If true, this would suggest that while the image is not being magnified (since the focal length of the lens is unchanged) there is an enlargement that effectively does make the image bigger even though there may be a loss in image quality,

I’ve tentatively confirmed the accuracy of the above by shooting a street sign from the same location with both 1.3X and a 1.6X crop factor cameras using the same lens, and in the case of the latter, the image appears to be larger and more legible. Go figure!

There is no magnification at all. It’s just an illusion because of the “crop” of a smaller sensor:

‘Crop’ is a fairly good term – the imaging area is physically smaller. Less of the image circle projected by the lens is used, therefore it is a crop. The image remains the same size at the film plane for a given lens and subject distance – it is in no way magnified. It does, however, take up a larger proportion of the (smaller) frame and so it is easy to see why some people call it a magnifying effect. This is also why a tele lens appears so much more powerful – the field or angle of view has been reduced…”

http://www.luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml

I was also wondering about the lessons, I’m very glad to hear they’ll be continuing

So don’t worry, the lessons will return, I just can’t give a reliable estimate as to when. Thank you for your patience!

The lessons were well written and fun to do and it would be sad to find out they have been cancelled, and I am sure others would feel the same way.

If they have been cancelled please accept my thanks for
what I have learned in such a short time.
Dot

I’m afraid that most of the books on optics I’ve read are well outside the bounds of photography… I think the best choice would be to look at the chapter on optics and lenses on a basic high-school-level physics book. It will have all the information you could ever need and it shouldn’t be too difficult to follow. Also you could check the wikipedia…

If you are really interested in these things, there is a great non-technical book I can recommend. It does talk about photography and lenses, but also goes well beyond that to discuss the nature of light, the functioning of our eyes, optical illusions, holography… It’s called ‘Seeing the light’, by David R. Falk, Dieter R. Brill and David G. Stork. It’s probably more than what you are looking for, unless you really enjoy this stuff. Or you could read only the chapter on photography, which I believe is self-contained.