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JohnHorne

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  • If you are interested you can look up formulae for calculating nearest point in focus and furthest point in focus based on focus distance, focal length , aperture etc.

    Put your chosen values into the formulae and you will find that the closer the focus distance the more equally the depth of field is distributed.

    For a particular focal length, aperture etc, you might then calculate the following values:

    Focus at 50mm, nearest point in acceptably sharp focus is 49.95mm, furthest point 50.05mm (depth of field is approximately 50% in front, 50% behind)

    Focus 100mm, nearest 99.8mm, furthest 100.2mm (dof approx 50 / 50)

    Focus 1,000mm, nearest 980.4mm furthest 1,020.4mm (dof approx 49 / 51)

    Focus 5,000mm, nearest 4,545mm, furthest 5,556mm (dof approx 45 / 55)

    Focus 10,000mm, nearest 8,333mm, furthest 12,500mm (dof approx 40 / 60)

    Focus 20,000mm, nearest 14,285mm, furthest 33,333mm (dof approx 30 / 70)

    Focus 30,000mm, nearest 18,750mm, furthest 75,000mm (dof approx 20 / 80).

    So, stating that the ratio is 50 / 50 for close-ups is a lot closer to the truth than saying that it is 1/3 / 2/3 for longer distances. (For most practical purposes focusing on any more than 20m to 30m is to focus on infinity.)

    The ratios calculated would be different for a different focal length and aperture, but the conclusion would be the same.
  • It's true. For close-up work depth of field extends approximately equal distances in front of and behind the plane of focus.
  • Silverprint sells Permajet paper (which is what I use) in A2 sheets and 17" rolls.
  • I find that the best solution is to use Google. Simply type the search terms in Google and then add site:www.ephotozine.com. Google's index is surprisingly up-to-date.
  • Do teams of people count ? If so, this group has come up with a unique and comprehensive set of images. Lots of technology involved.
  • A bit of a long shot but does your friend use OnSpeed or a similar service in an attempt to improve the performance of his internet connection ? If so, this works by compressing everything in order to reduce the volume of data sent. It even compresses JPEGs, which would, of course, have an adverse effect on quality.

    Also, don't forget that when sending emails with images attached Outlook offers the opportunity of resizing the image. If the sender selects this then, again, image quality will suffer.

    But, if nothing is compressing the images then quality won't suffer.
  • Elliot Erwitt took some snaps of dogs, and published a book called DogsDogs. (So good he named it twice ?)
  • As a general rule night-time photographs look better when there is still some colour in the sky rather than waiting until it is completely black. Have a look at [link=null]some examples of night photography [/link] in the gallery.
  • I used to keep a Skylight filter on the front of each lens, but now I omit them in preference of image quality. In the event of an accident I guess I would claim on the insurance ... the excess probably equates to the cost of a filter. A lens hood provides a certain degree of protection anyway.
  • Showing those images to a colleague reminded him that some food landscape photographs were exhibited at Southwark underground station last year. These pictures are in a rather different style, but still worth a look on the TfL website.
  • It's impressive stuff. A couple of his pics were published in the Sunday Times last weekend. His website shows more examples. (Visit http://www.carlwarner.com/warner.html. Unfortunately it uses Flash, but on the main page click on the second box, then on the next page click on the second folder.)
  • A number of exhibitions are listed here.
  • There is some very useful advice on this thread.
  • As a rough-and-ready calculation, you can calculate the film-to-subject distance, D (in millimetres), using the formula D = F x (M+1)^2 / M
    where F is the focal length of the lens in millimetres and M is the magnification.

    So if you know the magnification when using an extension thing and the magnification without, you can subtract one from the other to calculate the change in focus distance. (The Canon website gives maginification ratios for each lens with and without extension tubes.)

    Probably quicker to determine the change empirically though !
  • Gerald may be able to enjoy a debate whether a picture is of "Aquila chrysaetos on Pinus sylvestris" or "Erithacus rubecula on Quercus robur", but I suspect even Cheryl would rather get back to enticing Sciurus vulgaris within range using Arachis hypogea. Wink

    I notice that even the RSPB website doesn't give the Latin names except for family groups, so I think it's expecting a bit much for ePz members to do so !


    Quote:So what did we all decide?
    Good if you want to include it, but not a major crime if you don't


    That's probably best.
    Now, someone please help me complete the translation of "Homo sapiens sitting on fence" ...

  • Quote:40D can too

    OK !

  • Quote:Are you shooting lots of images when it happens?

    I don't think he/she shoots any images when it happens.
    Wink
  • The RAW files are the same size regardless of the JPEG file size selected on most Canon EOS cameras. I believe that the only Canon SLRs to offer a choice of RAW file sizes are the 1Ds Mk III and the 1D Mk III - though whether you can select RAW file size independently of JPEG size I don't know.
  • Multiple flashes is a technique I have used successfully in the past when doing macro work. Say my flash gun delivered enough power for correct exposure at f/11, but I wanted to use an aperture of f/22 to increase depth of field. f/22 lets in only one quarter as much light as f/11, so I set the lens to f/22 and fired the flash four times. Just make sure that you use a tripod and that nothing moves between flashes.

    A suitable analogy might be to think of multiple exposures on the same frame of film. Four exposures of 1/4 second each gives the same result (assuming nothing else changes) as a single exposure of 1 second.
  • My understanding is that if the photos are taken on private land then the owner can set the conditions that apply. For example, he may say that he is allowing you onto his land in order to take photos on the condition that you do not sell the photos elsewhere. However the fact that the photos were taken on private land does not mean that such a restriction automatically applies.

    To avoid any misunderstanding in future it might be worth seeking agreement in advance that you can do what you like with the photos.

    Regardless of any restrictions that may apply, the copyright remains with you (unless otherwise agreed).
  • Exhibitions listed here , many of which are in London.
  • Why not put them in a special area of your website and send them a link ? No printing costs, no folders to buy, no postage costs, earlier delivery ...
  • You can check the output using a flash meter. If the output is OK, then perhaps there is a timing issue. How do you trigger the studio lights ? If you are using a camera with a built in flash then perhaps it is firing a pre-flash which triggers the studio lights before the shutter opens.
  • If you visit CameraClubs.co.uk you can enter your postcode and it will tell you the nearest clubs to you.

    The North and East Midlands Photographic Federation lists clubs within its area.
  • Plenty of ideas here - just decide which images work for you.
  • Look on the bright side. At present the US Dollar is so weak that your payout would be less than 125. By waiting until the dollar strengthens relative to the pound, your payout will be worth more in sterling terms.

    You might be better off hoping that the next sale is not for some time ! Wink

  • Quote:The Canon 100mm for instance is a horrible portrait lens.


    Can you elaborate Keith ? Are you refering to usage ? Quality of results ?
  • Resizing at the RAW conversion stage might be a good idea if your software can do it. C1LE doesn't allow this - you need the Pro version.

    (Unless, the latest version of LE has been changed to allow this.)
  • This is a question which comes up regularly. Have a look at these forum discussions, which also include links to comparision reviews:
    - first
    - second
  • If I understand correctly you are saying that your image has enough pixels to allow you to resample to 18" long at 215ppi without interpolation ? If so, then you are throwing away data when you resize to 18" at 200ppi. You then attempt to recreate the discarded data (and more) when upsizing to 18" at 360ppi. If you insist on resizing in two steps then you would be better off going to 215ppi before going to 360ppi.

    However, I would suggest resizing to 18" at 360ppi (or your chosen final resolution) in one step, not two.