Focusing problems

JimM

I purchased a used Sigma 400mm f5.6 off of FM a couple of weeks ago. Because it is older and it only works wide open (at f5.6) the guys sold it to me for a great price.

Here is my problem: it seems to auto-focus just fine, but when I look closely through the viewfinder, the image is soft. I took some test shots, and sure enough, soft. Now the first time I did this it was like 15 degrees (F) outside, so I thought, well maybe somehow the warm lens caused the cold air to condense (I know, not really possible, but I hoped :dunno). So I went outside today upper 40's and sunny and tried test shots... again they look soft, but this time I tried manual focusing the lens too and I found the lens can get sharp. So here is my question:

Has anyone else ever noticed this (were manual is sharper)? Is there a solution? Is somehow the lens elements out of alignment for the focus? Any suggestions (aside from using this strictly as a MF lens)?

JimM

Update: I just tried auto focusing the lens on an older Canon film camera, an EOS 850 and it seems that auto focus gets it as sharp as possible.

wxwax

So you're thinking the lens itself isn't very sharp?

JimM

wxwax wrote:

So you're thinking the lens itself isn't very sharp?

No, just the auto focus when using this particular lens is not sharp. MF seems pretty good for the price of the glass.

Bob Bell

The older lenses dont have chips for new bodies so AF wont work or will only work at 1 aperture. That is why they are being sold so cheaply. I understand from a few threads that Sigma doesnt want to replace the chip but they have on occasion lately.

JimM

Hi Bob, thank you for the reply. The AF is working, it turns the lens and it gets it very close, just not dead on. You are correct at the aperature, as it will only work at 5.6, if I try to shoot above 5.6, the 20D gives me the Error99.

JimM

Update
I have just sent Sigma an email about the problem to see what they say. I will keep you posted on what their response is. In the meantime, if anyone has any ideas or suggestions on why it auto focuses soft, but will manual focus sharp (it is very close, just an extremely minor move to get it sharp), please let me know.

JimM

Sigma Update
Just received this (extremely fast) email from Sigma (looks canned to me)...

Thank you for your inquiry.
Unfortunately our older lenses have compatibility problems with some newer Canon cameras.
We regret to inform that your lens 400mm F5.6 is not compatible and can not be upgraded.
If you live in U.S., we have a 'trade-in' for lenses that can not be upgraded.
Please contact us at 1-800-896-6858 for more information (Monday through Friday, 9AM to 5 PM EST).
We apologize for the inconvenience.


I will try to call them tomorrow morning, but I have a feeling that the "trade-in" is not a large amount of money toward a new lens.

I still think it is strange how the auto focus is just slightly off and only on my 20D. If anyone has any suggestions, please let me know

JimM

Well, I called Sigma today... I will say I was reasonably happy with what they said, after all this is an older lens. They will offer a trade-in price for any one new lens I chose. They no longer make a 400mm, but they have a 300mm and a 500mm.

Prices for these:
300mm trade-in price was $2,031 (said it retails for $3,600, B&H has it for $2,600 )
500mm trade-in price was $3,229 (said it retails for $5,400)

So I think their trade in price is very good, unfortunately, I am not looking to spend a couple of grand on a lens right now.

So, like I said, I think Sigma is at least giving me a pretty reasonable trade-in on some new glass!

Maybe I can find another Sigma that I would be interested in and see what the trade-in price would be.

Bob Bell

JimM wrote:

Well, I called Sigma today... I will say I was reasonably happy with what they said, after all this is an older lens. They will offer a trade-in price for any one new lens I chose. They no longer make a 400mm, but they have a 300mm and a 500mm.

Prices for these:
300mm trade-in price was $2,031 (said it retails for $3,600, B&H has it for $2,600 )
500mm trade-in price was $3,229 (said it retails for $5,400)

So I think their trade in price is very good, unfortunately, I am not looking to spend a couple of grand on a lens right now.

So, like I said, I think Sigma is at least giving me a pretty reasonable trade-in on some new glass!

Maybe I can find another Sigma that I would be interested in and see what the trade-in price would be.

I must admit that I am impressed that Sigma would give you that kind of discount on a trade in. I think that lens worked fully on a D60 you should find one and see if it will AF.

DJ-S1

Sigma4less has the non-dg 300mm f2.8 for $2100 and the dg version for $2200.

I was just looking at the 14mm 2.8 myself - $750. Wonder what they'd give it to you for?

JimM

Hi Bob, I am impressed with Sigma here too. So if anyone is looking to buy a brand new 300mm 2.8 I might be able to work out a deal with you?

Okay... calling anyone with a D60 near the Detroit area... make yourself known! Anyone, anyone? Let's meet up and see if it works.

JimM

DJ-S1 wrote:

Sigma4less has the non-dg 300mm f2.8 for $2100 and the dg version for $2200.

I was just looking at the 14mm 2.8 myself - $750. Wonder what they'd give it to you for?

B&H has the 14mm for $849, so if I had to guess based on the other math, I would say $721.

JimM

DJ-S1 wrote:

Sigma4less has the non-dg 300mm f2.8 for $2100 and the dg version for $2200.

I am trying to check out there site, but it is painfully slow to me.

DJ-S1

Really? Pops right up for me. I've heard good stuff about them, DocIT recommended them to me. Never actually bought a Sigma I went for the Tamron instead, but their Sigma prices beat everyone it seems.