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Question on Minolta 24-85mm sharpness; is mine faulty?
Topic Started: Apr 9 2008, 09:21 AM (1,037 Views)
weishengg
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Hi all, recently i just purchased a secondhand Minolta 24-85mm f/3.5-4.5 lens for my Alpha A100.

When I got home and did my amateurish pixel peeping at some pictures i shot on my way home, i realized that the lens is either not focusing properly, or badly lacks sharpness at certain apertures.

I hope to seek advice from fellow forum members on what to do with regards to this.


Let me just highlight the problem first.
here are 2 test shots i did, camera tripod mounted, autofocused and focal length held. cropped >100% at the centre of the frame where it was autofocused at.

first one at 24mm f/3.5
Posted Image

second one at 24mm f/7.1
Posted Image



Another test set at 85mm, same procedure.

First one at 85mm f/4.5
Posted Image
Cropped image in centre
Posted Image




Second one at 85mm f/7.1
Posted Image
Cropped image in centre
Posted Image


Here are a few more test shots. Shot many many times and I'm pretty confident its not a matter of not autofocusing correctly. Its autofocus is quite consistent as far as I am able to detect.

1st set: 85mm, 1/125sec, f/4.5, ISO400, Flash fired
Posted Image
Centre cropped
Posted Image


2nd set: 85mm, 1/125sec, f/7.1, ISO400, Flash fired
Posted Image
Centre cropped
Posted Image



I am not very satisfied with this lens, but I just want to know if this is an inherent inferiority of the lens or had it been damaged and is still repairable?
what do you think?
weishengg.blogspot.com
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weishengg
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anyway apologies, i should have kept the exposure value of the towel test shots consistent. but i dont think it'll affect the sharpness of the image right?
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Ming
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Did you try shooting outdoor ? :unsure:
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weishengg
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alpha-ming9866
Apr 9 2008, 09:48 AM
Did you try shooting outdoor ? :unsure:

oh not yet, but should i expect to see any difference?

will take it out to shoot some pictures and examine again.
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Stvc
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weishengg
Apr 9 2008, 10:02 AM
oh not yet, but should i expect to see any difference?

will take it out to shoot some pictures and examine again.

Did you turn off your SSS when you mount on tripod?
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Tomato
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f4.5 is the widest aperture, some consumer grade lens aren't going to be as sharp wide open.

f7.1 is probably good for sharpness for this lens.

Though, my version is sharp at f5.6 onward.

Regards,

Hart
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bulldog
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hi,

ya.. agreed with hart..

when i open the aperature wide for shooting my spiders.. only the centre part or the head is sharp..

then when i down the aperature to F8 or higher, all seems clearer..

also today when shooting the IR @ LP.. i thought i open the widest so can shorten the explorsure time... result.. very blurr... close the aperature to F8 above.. all so clear again...
Darren Chin a.k.a Alpha-Bulldog...
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jasahchun
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bulldog988
Apr 9 2008, 08:32 PM
when i open the aperature wide for shooting my spiders.. only the centre part or the head is sharp..

then when i down the aperature to F8 or higher, all seems clearer..

bro.. what you say is the depth of field.. aka bokeh..

sharpness in consumer glass that hart is talking about is different.. :)
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bulldog
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jasahchun
Apr 9 2008, 09:21 PM
bulldog988
Apr 9 2008, 08:32 PM
when i open the aperature wide for shooting my spiders.. only the centre part or the head is sharp..

then when i down the aperature to F8 or higher,  all seems clearer..

bro.. what you say is the depth of field.. aka bokeh..

sharpness in consumer glass that hart is talking about is different.. :)

hi,

oh.. DOF....
Darren Chin a.k.a Alpha-Bulldog...
A550
18-55mm Kit Lens
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jasahchun
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路人甲
bulldog988
Apr 9 2008, 09:27 PM
jasahchun
Apr 9 2008, 09:21 PM
bulldog988
Apr 9 2008, 08:32 PM
when i open the aperature wide for shooting my spiders.. only the centre part or the head is sharp..

then when i down the aperature to F8 or higher,  all seems clearer..

bro.. what you say is the depth of field.. aka bokeh..

sharpness in consumer glass that hart is talking about is different.. :)

hi,

oh.. DOF....

ya..


do take a zoom glass out of your fridge.. just shoot normal staffs at different aperture.. you will see the differences in sharpness.. i got Tamron 17-50mm F2.8, but it's sharpest is around F4 onwards woh..
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