Why would one lens be more shadowy than another?

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loplyg

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Rich
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Hi folks,

I ran a series of test shots from a tripod today to decide which of two identical-purpose lenses I should keep, one of them being a pro 2.8 lens and the other being a realllly cheap plastic Nikon thing which is rumoured to be sharp.

The cheap lens is indeed every bit as sharp as the pro lens in every corner of the image, but for some reason the cheap lens renders shadows much darker than the pro lens. The exposure is the same throughout, just the dark areas are splodgier and darker on the cheap lens, whereas the pro lens somehow keeps them light and transparent.

I tried every combination of settings on the camera but it's always the same.

This is a tad annoying as it means you loose some detail in those shadows. Shadows can be darkened in PP easily, but lifting them is harder.

Anyway, for the price/size/weight difference I think it's a worthy sacrifice, but I'm curious as to why this happens.

Cheers,
Rich

PS Can you not attach images on this forum? Do you need an external host?
 
Okay here's some images which demonstrate the effect.

The lenses in question are the Nikon 35-70 2.8 (few hundred £ second hand) and the Nikon 28-80 G (£45 brand new!).

nz1.jpg


Note how the bottle in the background is more contrasty and the white lettering on the book is almost lost in the contrast.

http://www.cf-webdesign.co.uk/clientwork/nz2.jpg

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Note how the black handle on the knife (upper left) is almost a silhouette in the top image.

It's weird because the midranges and highlights are identical.

For your interest these two samples are taken from the absolute top right and absolute bottom left of the images, which is a bit of a shame as it means I have no reason what so ever to keep the 2.8 lens, being 2x as big, 6x as expensive and not having the same zoom range as its plastic cousin... It's not worth it for the extra brightness really :thinking:

Amazing how sharp the cheapy lens is. It feels like a box that you'd keep something in though, it's so rattly and plastic...
 
in the top one the better lens has better edge sharpness, you can see it in the writing.
 
I agree with Euan.

Are you using the same aperture and the same focus point in each image? It's no good comparing one thing shot at 2.8 to the same thing shot at 5.6 because depending on which AF point you're using you'll get depth of field differences
 
Yeah both shot at 5.6 with manual flash and shutter speeds. Carefully focused in tripod live view mode.

Bearing in mind the difference in size, weight and price, and that those crops are literally the ABSOLUTE corners of the image (and the centers are identical), I have to hand it to the smaller lens, which also goes 7mm wider and 10mm deeper...

Also, regarding edge sharpness, the 2.8 lens did a better job of the book (white on black edge), but on the ASDA receipt in the bottom images I think the cheap lens did better (black on white edge).

In a strange twist of fate it turns out the 2.8 has developed a rather serious autofocus malfunction anyway, so that sort of decides that one!
 
some lenses are contrasty...much would have been due to the coatings
dont know if this affects digital
 
"Note how the bottle in the background is more contrasty and the white lettering on the book is almost lost in the contrast."

I think you have just described the difference between a good quality lens and a not so good quality.

The better quality one has better contrast and better sharpness and the two together really make the difference.

Whether the difference is enough to justify the price is only a question you can answer.

EDIT: "In a strange twist of fate it turns out the 2.8 has developed a rather serious autofocus malfunction anyway, so that sort of decides that one!"

Yup - there is a God and he's taking the p**s!!
 
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Grumble... You mean to say that on a photography website you can't post a self-hosted picture that's 1070 pixels wide?

You can't even view BBC news unless your screen is 1024 wide...

Rules are rules :bonk:
 
I found the 37-50 sharp in manual focus, but rather annoying handling - the push pull zoom is something a bit weird to get used to if you haven't had a lens like that before, and the AF won't work properly upclose (it misfocussed a lot for me) - it's even mentioned in the manual (that, and the 80-200 AF-D if I recall).
 
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