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10-30-2016, 02:26 PM   #1
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Lens soft below f8

Hey everyone, I received a tokina 90-230mm lens off eBay last month and it takes great photos (it's the longest lens I have). One issue I have is that it is extremely soft and low contrast at any aperture below f8. Now I know the lens is old, but is there any reason for this? Is f8 the lenses' sweet spot? Its especially soft at 230mm at the lower apertures. Is it just designed like this? Th e birds look in focus through the viewfinder. I will upload some example photos when I can get to my desktop PC.
Thank you for your help and have a good one!

10-30-2016, 02:48 PM   #2
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I don't have that lens, but considering the well-regarded Tamron Adaptall-2 60-300 that I own - from the same era - I'd say that's fairly typical. Most of these older zooms are softer at the long end, and usually work best when stopped down to between f/8 and f/11. Also, a good general rule of thumb is to expect best performance some way before the maximum focal length. With your lens, I'd guess it starts to get softer past 150mm or thereabouts...

Long tele lenses have advanced greatly. There are some older tele lenses that are sharp at wider apertures, but they will have price tags to match

Last edited by BigMackCam; 10-30-2016 at 02:56 PM.
10-30-2016, 02:50 PM   #3
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Could you give an example of what you mean by an aperture 'below' F8 .... Are you meaning, for example, F11 ....or F5.6?

F11 is a smaller aperture than F8, and F5.6 is larger (in terms of diameter of the opening).

If, as I'm assuming, you mean the problem is with larger apertures (eg F5.6), then this is not uncommon with zooms, and more so with cheaper ones. There may be other optical deficiencies that become visible in certain lighting conditions also at the larger (wider) apertures. Ultimately it's a balancing act for you to decide on between image quality, stability and depth of field considerations.
10-30-2016, 03:16 PM   #4
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I own a new but 'cheapie' K mount Tamron 70-300 and it is the same with it. Acceptable sharpness beyond 200mm pretty much requires F8. OTOH, the Pentax 60-250 F4 is superb wide open, at all focal lengths, but you pay an additional $1000.00 or so more for it.

10-30-2016, 04:23 PM   #5
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QuoteOriginally posted by mcgregni Quote
Could you give an example of what you mean by an aperture 'below' F8 .... Are you meaning, for example, F11 ....or F5.6?

F11 is a smaller aperture than F8, and F5.6 is larger (in terms of diameter of the opening).

If, as I'm assuming, you mean the problem is with larger apertures (eg F5.6), then this is not uncommon with zooms, and more so with cheaper ones. There may be other optical deficiencies that become visible in certain lighting conditions also at the larger (wider) apertures. Ultimately it's a balancing act for you to decide on between image quality, stability and depth of field considerations.
Aah so sorry, I got it round the wrong way! I mean wider apertures like f5.6, f6.7 and f4.5. It is really soft in these apertures. Cheers!

---------- Post added 10-30-16 at 04:25 PM ----------

QuoteOriginally posted by BigMackCam Quote
I don't have that lens, but considering the well-regarded Tamron Adaptall-2 60-300 that I own - from the same era - I'd say that's fairly typical. Most of these older zooms are softer at the long end, and usually work best when stopped down to between f/8 and f/11. Also, a good general rule of thumb is to expect best performance some way before the maximum focal length. With your lens, I'd guess it starts to get softer past 150mm or thereabouts...

Long tele lenses have advanced greatly. There are some older tele lenses that are sharp at wider apertures, but they will have price tags to match
Oh, ok. I thought it was because it is so old, but just wasn't sure why! Thanks

---------- Post added 10-30-16 at 04:26 PM ----------

QuoteOriginally posted by CDW Quote
I own a new but 'cheapie' K mount Tamron 70-300 and it is the same with it. Acceptable sharpness beyond 200mm pretty much requires F8. OTOH, the Pentax 60-250 F4 is superb wide open, at all focal lengths, but you pay an additional $1000.00 or so more for it.
Interesting to see that it happens with new zooms too! I won't be able to afford the 60-250 for a while! Haha
10-30-2016, 04:37 PM   #6
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QuoteOriginally posted by bessa-66 Quote
Hey everyone, I received a tokina 90-230mm lens off eBay last month and it takes great photos (it's the longest lens I have). One issue I have is that it is extremely soft and low contrast at any aperture below f8. Now I know the lens is old, but is there any reason for this? Is f8 the lenses' sweet spot? Its especially soft at 230mm at the lower apertures. Is it just designed like this? Th e birds look in focus through the viewfinder. I will upload some example photos when I can get to my desktop PC.
Thank you for your help and have a good one!
The image quality generally starts dropping at around F11 due to diffraction, so this sounds more or less normal.

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