Page 2 of 2 FirstFirst 12
Results 11 to 19 of 19

Thread: Digital photography

  1. #11

    Join Date
    Dec 2005
    Location
    Southern California
    Posts
    2,736

    Digital photography

    Dave, thanks for the tip, I made a note of it and I'll try it as soon as I get another digital camera. I use the latest Photoshop, but old habits are kinda hard to "unlearn". I do presharpening as well, but was hesitant to recommend it because it compensates for the Bayer sensor and to be honest, I'm not sure if the digicams are using it or not. Besides, lots of first time users tend to overdo it (I did) and it would serve no purpose in this particular case.

    But we better be careful discussing digital, lest we get our hides drummed out of this board

    Best regards,

  2. #12

    Digital photography

    Do you suppose the title of this thread might help the people who would rather not read about things digital---will it help them steer clear? Anyway, this thread contains some good information for anybody, including large-format users, who wants large prints from digital files.

  3. #13

    Digital photography

    Hey Jerry,

    I'm just heading out for ribs....so the paragraph will have be done later. I have been doing that routine and ones like it for quite a while. I then happened upon the article quoted above & I think it explains things better than I can.

    I'll go into more depth later....now on to the ribs......

  4. #14
    grumpy & miserable Joseph O'Neil's Avatar
    Join Date
    Feb 2004
    Location
    London, Ontario
    Posts
    830

    Digital photography

    The issue regarding megapixels and enalrgement can be misleading.

    What is often much more important is the *actual pixel size* of the sensor/chip in the camera used. First off, is it a CCD or a CMOS chip/ At 7 megapixel, likely a CCD chip, but not all CCD chips are created equal.

    then you have the quality of the chip itself - how prone it is to noise, hot pixels, etc.

    these just are some of the reasons why two cameras, say both 5 meg or 7 meg, can have very different prices.

    another issue is lens quality. I have what woudl be considered a low quality digital camera - "only 3 megapixel" as I ahve been told, but the lens is a 12 element lens with ED glass. I find because of the high quality of the lens, and becasue of the high quality of the CCD chip, it outperforms other 4, 5 and even 6 megapixel cameras.

    The big problem is finding out. You may find, as i have, that once you start getting into some of the technical questions - "what's the pixel size", a lot of these bright eyed sales clerks start to falter.

    One last thoguht - megapixels do not account for other factors such as tonality. A photograph can be very grainy but still have wonderful impact. One of my personal favourites that I ever printed is a 16x20 enlargement fomr a 35mm neagative- HSI at that. grainy as hell, but the ontality 9at least for me) is just great, and the overall effect of the coarse grain witht he "dreamy" look of th einfra-red film just works great for me in that specific shot.

    so don't get too caught up in grain - film or digital - look for the tool that will give you the art that you are seeing in your head and want to put to paper.

    joe
    eta gosha maaba, aaniish gaa zhiwebiziyin ?

  5. #15

    Digital photography

    Jerry,

    Sorry to not write back sooner....but you can't keep me away from a nice rib dinner!

    The process I mentioned above can can work just fine in RGB mode with all the color channels. I have taken it one step further. I convert to lab mode, and have the luminosity and the Alpha A & Alpha B channels worked on seperately.

    The luminosity channel is processed as I mentioned above.....with the exception of the "fade - Luminosity" part of course.

    The Alpha A & B channels are processed basically as follows:

    - Presharpen 300, 1.4, 4
    - Bicubic stair step to desired print size

    The 3 different channels are then opened all at once in photoshop, and through layers are combined in to one image and converted to lab, and then RBG.

    Working with Alpha channels is tricky as the results you see on screen rarely correspond to what you get in the recombined RBG image or on print. You get a feel for it after a while. The above settings are just a starting point.

    Watch the following:

    Sometimes presharpening is not best. Then simply leave it until after interpolation and then be a bit more aggressive. If presharpening, don't go higher than about a 1.5 pixel width as you'll get color bleeding into the luminosity channel after recombining. Keep you threshold above 3 at least....pref 4 or 5 to avoid increasing noise on the Alpha channels.

    As I said, this does give you a bit more noise that can sometimes be visible on screen at 100%.....but this only rarely shows up on print. If it is a concern, I run the Alpha channels through Neat Image with a very light noise dusting. This makes it even more convaluted, but it can be effective & I see no reduction in detail.

    In the end, what I see as a difference is that I tend to get what appears to be a more natural look to the image.....more film like if you prefer, as opposed to a video like look when people follow a very basic workflow. I find it reduces halos, helps with specular highlights, and in the end, gives me better output for the sizes I normally print from a 1Ds, which is 16x24 & 20x30.

    Also, while this works well on Canon CMOS based sensors, I find that it does not work as well with Nikon CCD sensors. Nikon's images have a bit more noise to them.....which on its own is not a problem. When luminosity channels & Alpha channels are processed like I said on a Nikon image, I find about an extra 1 to 1.5 stop disadvantage in noise when compared to Canon cameras. Because of this, when working on Nikon images, I skip the seperate Alpha processing and just work with the original flow I mentioned a few posts up.

    Sorry to be wordy, but there ya go.

    Best regards,

  6. #16

    Digital photography

    Dave, thanks so much! I wonder why you sharpen the A and B channels (with CMOS images) at all. I also wonder at the stair interpolation of A and B. I thought sharpening these two channels was seldom needed or wise. What goes wrong if you simplify these away?

  7. #17

    Digital photography

    Jerry,

    I sharpen the Alpha channels with a larger pixel width to avoid noise. Using the values that I do on the lumi channel would increase color speckling on the alphas. By selecting a lower % but higher pixel width, I find a more natural appearance in the final product.

    As to stair stepping, I found that because their is less detail info in the alpha channel, I am able to be a bit more aggressive on the interpolation part to maintain what detail there is, without having to worry about halos, jagged edges, or noise. While stair stepping can show more noise and haloing on the lumi channels, it doesn't appear to have that effect on the alphas. This final step with working on the alpha channels is subtle at best, and invisible most of the time. But in some highly detailed photos, I like the final look of the image more than the simpler routine. I don't bother with the extra work when setting up to print portraits or wedding formals. But when I'm doing some of the landscape work I do, I always give it a try to see if there is a difference that I prefer.

  8. #18

    Join Date
    Mar 2005
    Location
    Baton Rouge, LA
    Posts
    2,428

    Digital photography

    You should look into using PkSharpener, a plug in for photoshop that does a very good job of optimizing sharpening, with a lot less trouble.

    The image makes a lot of difference. Something without fine detail - cala lilies - will look great because of the smooth texture of digital, while something with a lot of detail - trees - will emphasize the limited resolution and pixelation.

  9. #19

    Digital photography

    Ed,

    PKSharpener is fine for RGB images, but it is not optimised to handle Alpha channels and as such, wouldn't be a good choice for the workflow I mentioned. It would be a fine solution for the worflow if you were staying in RGB, but I don't believe I can make the plugin part of an action, and as such I would have to stay the USM.....which can work equally as well as long a s the operator knows what they're doing.

    As well, with trees and such targets that require fine detail, it does come down to printing size. The best DSLRs can now easily make 16x24 & 20x30 that have a good amount of detail. You would never have "pixelation" in the image as long as interpolation & sharpening is done right. Increasing the size of digital images with properly done interpolation just results in an image that becomes increasingly softer as output size grows.....pixelation only occurs with poorly done processing.

Similar Threads

  1. digital back and architectural photography
    By goran in forum Digital Hardware
    Replies: 11
    Last Post: 15-Dec-2009, 00:32
  2. Contemporary Photography boom - digital or b&w?
    By tim atherton in forum On Photography
    Replies: 29
    Last Post: 11-May-2008, 03:35
  3. digital vs traditional photography
    By Ellis Vener in forum On Photography
    Replies: 155
    Last Post: 18-Jul-2005, 05:33
  4. is there any traditional photography digital can not replace?
    By Jeff Liao in forum Digital Hardware
    Replies: 15
    Last Post: 18-Apr-2002, 09:04
  5. Digital Backs for large format photography
    By Eleanor Skan in forum Digital Hardware
    Replies: 5
    Last Post: 26-Sep-2001, 14:03

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •