Yes, I have the same question. I'd have thought that measuring a 1mm
focus error at 300mm would be nearly impossible due to depth of field.
However, maybe not. The 150mm f/2 DOF at f/2 and 300mm focusing
distance is only +/- 0.1 mm. However, that lens won't focus anywhere
near 300mm without a lot of extension help. The 35/3.5 macro will
easily focus that close but the DOF at f/3.5 and 300mm distance is about
+/ 3.5mm.
Chuck Norcutt
C.H.Ling wrote:
> BTW, I'm very interested on your setup, how can you measure the 1mm error at
> 300mm distance? Were you using a macro?
>
> This is the best I can do (both use center focusing point):
>
> Normal AF
>
> http://www.accura.com.hk/temp/PC210741.jpg
>
> Imager AF
>
> http://www.accura.com.hk/temp/PC210742.jpg
>
>
> C.H.Ling
>
> ----- Original Message -----
> From: "C.H.Ling" <ch_photo@xxxxxxxxxxxxx>
>
>> It is a rough figure but not far away, here is an example at 14mm setting,
>> the overall image may not be very sharp due to slow shutter speed but you
>> can see the focus is on the dish (or the drink) while it should be on the
>> face.
>>
>> http://www.accura.com.hk/temp/PC090020.jpg
>>
>> If focus shift is due to sensor positing error in the vertical plan (i.e.
>> just up/down or left/right) it is ok as the target will still be sharp. I
>> will not accept any focus shift which will cause image softness.
>>
>> C.H.Ling
>>
>>
>> ----- Original Message -----
>> From: "Frank van Lindert" <Frank@xxxxxxxxxxxxx>
>>
>>> CH, is it _really_ as bad as that, 2 ft instead of 3 ft, or are these
>>> figures just serving as an example of the phenomenon? If the figures
>>> are from real life, then I would return that E-520 immediately and
>>> not even bother having it repaired or consider to buy another.
>>>
>>> I own a E-400 and the focusing error is only 1 mm when the actual
>>> object distance is 300mm. Or to put it (roughly) in those terrible
>>> imperial measures, the error equals 1/32 inch at a 1 foot distance.
>>> Quite acceptable, I would say ;-)
>>>
>>> How much is the real error with your E-520?
>>>
>>> Frank van Lindert
>>> Utrecht NL.
>
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