Comments made by johnriley - Page 1788

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You have it set to a mode (such as green mode or P) that does not allow these functions?

Comment by johnriley posted on greyed out menu items-K20D at 25/04/2009 - 17:33

Quote:
The 16-45 is basically a inverted telelens.

All SLR wide angles are inverted telephoto designs (retrofocus) so that enough space is available for the mirror assembly. This isn't the reason for the reversed construction of the zooming mechanism.

Wide angles for rangefinder cameras are so tiny because they can be designed with the rear element very close to the film plane. This also makes them easier to manufacture, with fewer elements.

Comment by johnriley posted on Pentax 16-45mm at 25/04/2009 - 16:01

It's the reverse of what you might expect.

There was also a Voigtlander 50mm Ultron lens that had a concave front element - that looked strange as well.

There's always a good optical reason for these things. In the case of the Ultron it had much better edge definition. The 16-45mm performs very well, whatever the reason for the strange contruction!

Comment by johnriley posted on Pentax 16-45mm at 25/04/2009 - 15:53

It's easier to prefocus on a spot using manual focus and then you don't need to keep your shutter button half depressed. Just pan with the car and release the shutter just before it reaches your focus point, continuing to pan beyond the shot being taken.

The reason for releasing the shutter slightly early is to allow for the shutter delay. The reason for continuing to pan is to ensure the panning remains smooth throughout.

Comment by johnriley posted on Manual or Auto Focus for Motosport at 25/04/2009 - 14:03

I'm currently using the 28-80 Power Zoom for all my eBay pictures and it's a fantastic lens. I've seen indifferent comments about it on the Internet, but my sample bears out the excellent test result that AP published when the lens first appeared.

Comment by johnriley posted on Novice, basic lens questions? at 25/04/2009 - 12:47

Can I remind everyone that this is the Classified Ads section and it's not helpful to sellers or buyers if there's a dissection of the rights and wrongs of a price or product.

There are more appropriate sections for those sorts of discussions that won't undermine people's attettempts to offer items for sale.

I shall be deleting off-topic comments in future.

Comment by johnriley posted on Sigma 10 - 20mm at 25/04/2009 - 11:59

If you focus on the sign and take images at various apertures the sharpness of the wall behind will vary because the depth of field will change.

Comment by johnriley posted on Here at last! - DA* 60-250 at 25/04/2009 - 11:56

True, but in this context we're not really talking about the Tescos of this world, who are rather bigger fish!

It's an oddity of the UK that "profit" seems to be a dirty word. If someone makes money it seems OK, as long as in our perception they don't make too much money. In the USA making a huge profit might bring a response of Well Done, here it might be They Should Be Taxed More.

Odd world really.

Comment by johnriley posted on Prices on the Pentax X70 at 25/04/2009 - 11:49

Fair enough, the proof of the pudding, etc....

Comment by johnriley posted on shipping ebay items from U.K. to abroad at 25/04/2009 - 11:45

Thanks, that may well be so. The Power Zoom idea never caught on for SLR lenses, but it went on to be used in just almost every compact and bridge camera!

Comment by johnriley posted on Novice, basic lens questions? at 25/04/2009 - 10:50

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