Digital BW, The Print

Michael,
I'm sliding in a tad late but it seems, to me anyway, that it's getting hard to see the forest thru the trees in this post series... lots of good thoughts.. 
Ok first what is sharpness (sorry) ..For me it is about contrast between various tonalities in a minimum with of pixels such that the perception of sharp is achieved..  So a transition over 5 pixels will be perceived very differently then a transition over 15 pixels.. When we look at image on the screen we actually don't get to see it on size we see a version that is show at say 72 dpi.. then interpolated by the video card to show us it's interpretation of what that image might look like as we make it smaller on our screen..  So in your effort to compare the sharpness of two scans done at different resolutions I think looking at the entire image on your screen is causing one to get lost..  I would check a few areas of each image at 100% ..in other words at a pixel level and literally note or count the pixels for a given area of both do the transition... I realize this may be subjective at times but it works..  ..In the end one might say it's meaning less but that will help you understand the variance.. Lets say one is a 6 pixel transition and the other is an 11 pixel transition.. To me this in information but not really that valuable in the end unless you interpolated the larger image down and got a bump of a smaller pixel transition then the smaller original scan. Typically larger prints reflect a greater viewing distance..so it's really not appropriate to say, in my opinion, both items will be viewed from the same distance ..but I guess they could be.. Lastly, the proof in the pudding is not the screen it's the print.. The reason I say that is that again your video card scales images on your screen ..but we've all seen jaggies on screen and none in a print. The video card is a rendering of the image at various sizes.. Only when viewing it at 100% can you see sharpening artifacts properly.. As technicians we must learn thru experience to be able to understand what we see.. B&W is really incredibly different then color imagery.. Color can use itself to show different object transitions by just using a different hue to do it.. B&W has only shades of gray to do the same job so we must learn to use that to it's maximum to show all that is in an image. That's going away from your inquiry I guess but to me it a part of it as when we push to make these transitions happen we also can get into messing with perceived sharpness at times. Anyway spending the time on screen to evaluate two tree branches at different resolutions in their entirety may not be the best use of time. Simply check a few areas one to the other for transitional length followed by maybe small proofs showing those areas..

jimbo

----- Original Message ----- 
  From: Michael 
  To: DigitalBlackandWhiteThePrint@yahoogroups.com 
  Sent: Tuesday, July 06, 2010 8:31 AM
  Subject: [Digital BW] Re: Scanning b&w negs, revisited


    
  Thank you Tony, Lincoln and others. What is getting lost is my original question: "The question I have is how do I best evaluate - on screen -
  scans of the same frame made at two different resolutions?" Before you say to view at actual pixels, I know that part of the answer. But I think it's more complicated than that. Viewing a 6 foot length of tree branch at actual pixels from 2 differently sized scans makes that same length of branch different lengths, in inches, on the screen. This makes it hard to look at the same section and make a direct comparison. It the lower rez scan is magnified beyond actual pixels then interpolation(?) from software becomes an issue. But without a same sized, side by side comparison of the two scans, how do I best evaluate them? 



  

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