Just be sure to hold the same resolution when it comes time to print.
Chuck Norcutt
Wayne Harridge wrote:
> Thanks, that's pretty clear and also agrees with AG's .2mm for 10x8.
>
> ...Wayne
>
> Wayne Harridge
> http://lrh.structuregraphs.com/
>
>
>> -----Original Message-----
>> From: Chuck Norcutt [mailto:chucknorcutt@xxxxxxxxxxxxxxxx]
>> Sent: Saturday, 18 July 2009 10:07 PM
>> To: Olympus Camera Discussion
>> Subject: Re: [OM] Scanner DOF
>>
>> I think the answer I gave you is the correct one but if you want to
>> understand it in terms of human vision (which is the basis for CoC)
>> then
>> I refer you to this wiki link which discusses that.
>> <http://en.wikipedia.org/wiki/Circle_of_confusion#Circle_of_confusion_d
>> iameter_limit_in_photography>
>>
>> Depending on what assumptions you make you'll end up with slightly
>> different answers but the article mentions 5 line pairs per millimeter
>> at a 25cm viewing distance as a commonly accepted value. That's 10
>> pixels per millimeter or 254 pixels per inch. That's also why I
>> recommended 300 pixels per inch for the scan. That's the closest,
>> commonly available scanner resolution that equals or exceeds that. But
>> now that I know you have a V700 (which I also have) I know that you
>> could also scan at 240 or 266 or 350 or more if you desire. 300 is
>> generally considered very good for prints up to 8x10. 240 is good for
>> larger prints which will be viewed from farther away.
>>
>> Chuck Norcutt
>>
>>
>> Wayne Harridge wrote:
>>> Let me try to clarify what I am asking.
>>>
>>> I have 2 scanners, a cheap multifunction unit (scanner, printer,
>>> copier,...), I know it has very little DOF. I also have an Epson
>> V700 which
>>> has much greater DOF. For something to be perceived as "sharp" by
>> the human
>>> eye, what is the size of the CoC required on a print ? I'm sure it
>> was
>>> mentioned on this list at some stage but can't remember the actual
>> value.
>>> The answer will determine how "deep" the object on the flatbed can be
>> and
>>> still be perceived as sharp by the viewer of a print.
>>>
>>> ...Wayne
>>>
>>> Wayne Harridge
>>> http://lrh.structuregraphs.com/
>>>
>>>
>>>> -----Original Message-----
>>>> From: Chuck Norcutt [mailto:chucknorcutt@xxxxxxxxxxxxxxxx]
>>>> Sent: Saturday, 18 July 2009 12:58 PM
>>>> To: Olympus Camera Discussion
>>>> Subject: Re: [OM] Scanner DOF
>>>>
>>>> I'm really not sure I understand the question since I don't
>> understand
>>>> it in terms of DOF. Some flat bed scanners have a very great DOF of
>>>> maybe 6mm or more from the surface of the glass which is great for
>>>> scanning 3D objects. Others, not so much. So, the DOF is what it
>> is
>>>> and you won't be able to change it. It's not as though you can
>> alter
>>>> it
>>>> by changing aperture or anything else except that some scanners can
>>>> alter focus distance. So with the right scanner it might be
>> possible
>>>> to
>>>> do multiple scans and blend the layers. But I don't know if
>> scanners
>>>> can really change focus distance enough to make that practical.
>>>>
>>>> But what I read into your question is something different. It
>> sounds
>>>> more like you're asking what scanning resolution you should use to
>>>> maintain a good life-size replica of whatever you're scanning. For
>>>> example, you want to scan a pencil which is 15cm long and print it
>> on
>>>> paper at 15cm while having it look nearly as sharp as the real thing
>>>> when viewed from a distance of about 25cm. A resolution of 300 ppi
>>>> should be adequate for all but Moose. If you want to please even
>> Moose
>>>> go to 600. Even he can't see better than that. :-) But remember
>> to
>>>> sharpen the final image at print size before printing.
>>>>
>>>> Dr. Focus
>>>>
>>>>
>>>>
>>>> Wayne Harridge wrote:
>>>>> Probably a question for Dr Focus.
>>>>>
>>>>> I'm wanting to scan some 3D objects on a flatbed and wondering how
>>>> much
>>>>> depth of field I need. Assuming the resultant print is "life size"
>>>> (i.e.
>>>>> ~A4) what vale of circle-of-confusion should I be using. This
>> should
>>>> be
>>>>> related to the resolution of the human eye at a normal viewing
>>>> distance I
>>>>> think - so what is that value ?
>>>>>
>>>>> ...Wayne
>>>>>
>>>>> Wayne Harridge
>>>>> http://lrh.structuregraphs.com/
>>>>>
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>
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