Question about going digital

Discussion in 'Beyond the Basics' started by Vinny, Mar 14, 2010.

  1. Vinny

    Vinny TPF Noob!

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    Hi all,

    I'm new to this site and new to digital SLRs but have been an amateur photographer off and on for about 30 years. My equipment has been a Nikon FE with 2 sets of Vivitar zoom lenses - a low focal length and a medium focal length along with a 50 mm Nikon lens that came with the camera. I was convinced back then that zoom is the way to go and I guess I still am.

    I am deciding whether to buy a digital SLR and it seems that photography has "changed" since I first learned it and have some questions.

    My questions are:

    I'm reading that the digital zoom ranges are different than film. Based on what I've read the sensors on digital cameras are smaller than 35mm film so the image is magnified and gives the lenses a higher focal length. Is this correct?

    I read a lot about image stabilization lenses/cameras and I believe this is a good thing for point and shoot but back in the day the rule was to keep the shutter speed at 1/(focal length) to keep the image sharp if holding the camera. I do understand that image stabilization can provide a sharper images at slower shutter speeds which is a good thing. I've seen some forums where photographers argue the point of image stabilization -Does digital photography need image stabilization to have sharp images?

    At the level I am looking at (Nikon D5000 or Canon EOS T2i) how important are the mega-pixels? I know that the higher the mega-pixels the sharper the image but I wont be blowing up an image past a 8x10 size. Again, in film you used ASA settings (now known as ISO) and the smaller the ISO the finer the grain of the film.

    Speaking of ISO, what is the purpose of ISO setting in a digital SLR? In film, the ISO would keep the exposure correct for the film speed. In digital I would think that the sensor is a fixed megapixel and it wouldn't matter.

    Well, thanks for your help and I'm sure that there will be more questions!

    Vinny
     
  2. BKMOOD

    BKMOOD TPF Noob!

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    ISO is digital equivalent of ASA in film -- it measures sensitivity to light. ASA is a term used to describe film's sensitivity to light. ISO is a term used to describe a sensor's sensitivity to light. They are basically the same thing. Where a high ASA in film increase film graininess, a high ISO in digital increases digital noise.

    Image Stabilization can either be in the body (like Sony Alphas) or it can be in the lens (like Canons). Image stabilized lenses are more expensive than non stabilized lenses. With Sony cameras, all lenses are stabilized because the stabilization takes place in the body of the camera. Which is better is a personal choice and preference. Image stabilization is just a helping hand. A skilled photographer can get very sharp pictures without it.

    As for megapixels... Unless you're blowing up pictures beyond 8 x 10, you really don't need more than 6 or 8 megapixels. The guy at the store, of course, will try to sell you 1000 megapixels if he could. For this, I recommend you just type in "The Megapixel Myth" into google and read a few articles. More isn't necessarily better, especially when you squeeze more pixels on to a smaller chip. They can be less effective. Picture quality is dependent on many, many factors like sensor size, firmware, how big those pixels are, your skill as a photographer and so forth. Don't buy into the blanket "more pixels is better" statement.

    Before you buy anything, I recommend reading a book or two about digital photography. There are a number of basic books out there that will give you a great overview. Nothing wastes money faster than poor information. Sales people love customers who don't know much. That way they can sell you anything! Walk through the door well informed.

    As for sensors... Well, I'll let someone else tackle that one. My old hands need a typing break.
     
    Last edited: Mar 14, 2010
  3. djacobox372

    djacobox372 No longer a newbie, moving up!

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    You might want to consider a used nikon d200, as it will be fully compatible with the nikon lenses you already own. The d5000 will mount those lenses, but it the light meter in the camera won't work with them.

    You are right about most dslr's cropping the image a bit, typically they are about 2/3rds the size. This is nice on telephoto's as it makes them longer, but at the expense of DOF. For example your 50mm f1.8 lens will take photos like a 75mm f2.8 on a crop-sensor dslr.

    The higher end dslrs, d700 d3, have no crop factor--they are "full-frame" which means the sensor is the same as 35mm film. The benefits of "full-frame" are a smaller dof at the same shooting distance, and increased light sensitivity (you can shoot at iso 3200 with very little noise).
     
  4. KmH

    KmH Helping photographers learn to fish Supporting Member

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    The focal length of a lens, is the focal length of the lens.

    A crop sensor digital camera gives a narrower field-of-view (FOV) than the same lense would give on a 135 format (35 mm) film camera.

    So, a 50 mm prime, or a zoom that has the focal length set to 50 mm, on a camera having a 1.5x crop factor would give the same FOV as a 75 mm focal length would on a 135 format camera. 50 mm x 1.5 = 75 mm.

    Nikon small sensored cameras (APS-C size sensor) have a 1.5x crop factor.
    Canon small sensored cameras (also APS-C size) have a 1.6x crop factor and that 50 mm focal length gives a equivelent FOV of 80 mm.
    Olympus cameras have a 4:3 aspect ratio sensor that is even smaller and gives a 2x crop factor.

    135 format and the APS-C size sensors have a 3:2 aspect ratio.
     
  5. Vinny

    Vinny TPF Noob!

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    My lenses are not auto-focus and I would like to get a SLR that auto-focuses due to my family not taking good pictures (I'm thinking an advanced point and shoot for them). We recently went to a couple of weddings and a few people had DSLRs and the images were fantastic; the pictures my family took were not! I realize that a small point and shoot is no match for a SLR but even up close they weren't too good. I also wear glasses and it is a little bit of a chore to focus the lens. I like the idea of the ability to take creative shots (haven't looked at any cameras yet) when I want to and if it takes me a little longer to focus - no big deal.

    "For example your 50mm f1.8 lens will take photos like a 75mm f2.8 on a crop-sensor dslr." VS "A crop sensor digital camera gives a narrower field-of-view (FOV) than the same lense would give on a 135 format (35 mm) film camera." The first quote is what I'm saying and the second quote sounds as if the image would be the same as a film image except the field of view would be less; not sure if both quotes are saying the same thing.

    I did some research on the ISO in digital and it seems that all it is doing is making the sensor more sensitive to light (and noise) - same as going up in film speed.
     
  6. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Yep.

    The only difference is that ASA was the name of an American standards agency and ISO is the name of a French standards agency, both measuring the same thing.
     
  7. KenC

    KenC Been spending a lot of time on here!

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    Vinny-
    I have a similar history in photography and converted to digital myself gradually over the past few years. ISO in digital is similar in that using a higher setting allows you to use a faster shutter speed and/or smaller aperture, but the trade-off is more noise (equiv. of film grain). However, the sensors in DSLR's are so good, that in my experience, the 1600 setting (highest I have in my Canon XTi) has less noise than I used to get with 200 speed film, which was slow film to me, since I often shot 400 or even 800. I routinely walk around with my XTi set to ISO 800 unless I want to restrict DOF or there is just too much light. I usually make about 8x10 - 11x14 prints, so if you want to go larger, then you obviously would need to go a little lower than I do in ISO. Also, just for info, the digital noise manifests as grain and also color noise (random bright colored pixels). I used to see something like this color noise with very high speed film, but I think it's a little more prevalent in high-ISO digital.
     
  8. Dwig

    Dwig TPF Noob!

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    The two quotes are basically saying the same thing. Your statement that "the image would be the same as a film image except the field of view would be less" is obviously incorrect. Two things can't both the the same and be different. If the FOV is different the images aren't the same.

    The image format used by the common "crop sensor" digital SLRs is about the same amount smaller then standard 35mm film as standard 35mm film is compared to 6x4.5 or 6x6 medium format 120. The issue of lens focal length and FOV is the same. Just as Rolleis and Hasselblads had 75-80mm standard lenses and 35mm full frame cameras had 50mm standard lenses the same "standard" lens would be around 28-35mm on todays crop sensor DSLRs if zooms hadn't replaced prime lenses as the standard "kit" lens.

    As to some of your other questions:

    1. ISO is important to DSLRs. Its a measure of the sensor's sensitivity to light, not its resolution. Adjusting the ISO to higher values increases the electronic noise. This noise is somewhat similar to grain in film. Even though the number of megapixels is fixed, the noice level reduces image quaity and you often want to avoid the higher settings. So in general, the same rules apply with both digital and film. The higher the ISO the lower the image quality, both increased noise/grain and decreased tonal range.

    2. Image stabilization is valuable. The common zoom lenses that you'll see today are quite a bit sharper than the ones from the time period of the FE, but one of the compromises they have that allow them to be good and inexpensive is that they are slow. Many common zooms are as slow as f/4.5 or f/5.6 at their longer focal lengths. You often find is difficult to maintain a decent shutter speed despite the somewhat higher ISOs the digital allows. Image stabilization can often allow you to shoot at 2-3 stops slower shutter speeds than you could without it.

    3. Megapixels are one of the least important factors in determining the quality of the image produced by DSLRs. It is one of the easiest to measure and explain which makes it the common bragging point. When comparing cameras, ignor any MP difference that is less than a 50-80% difference. If you are really going to stay with 8x10 as the largest then anything over 6mp is only giving you the luxury of cropping more later and still retaining quality.
     
  9. Vinny

    Vinny TPF Noob!

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    OK, I learned something today! Thanks!! I never knew that the larger format cameras had larger focal length standard lenses, I never thought about it and just assumed the lens was just physically larger on a larger format camera.

    So field of view is the correct measurement of a lens vs focal length? I equated field of view with the angle in which the lens sees, such as 18mm equals wide angle and a 600 mm equals very narrow angle. Even at both of these extremes the image can be cropped for a narrower field of view ... then I guess to get to a standard size the image would be magnified.
     
  10. Romphotog

    Romphotog TPF Noob!

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    Dont worry about MPs; an 8MP DSLR is enough even for weddings.
    Noise/artifacts are reduced by using lower ISO. More MPs simply increases size of pic [aka resolution]. ISO400 is 4x noisier than ISO100.
    More MPs are useful when cropping.

    Also, use RAW if pics are real important, otherwise use jpg Fine or Normal.
    However, in a test I zoomed Normal 200%, looked ok, less distortion than Economy.
    In fact, if you have to zoom that much to see so little difference between Fine, Normal, and Economy, it's not worth it to use Fine at all as file size
    is 3x. I use Normal as I found burst mode using Fine useless as it took too long to save to card.
     
  11. Vinny

    Vinny TPF Noob!

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    After asking these questions, I've been doing some more research and I'm have learned some more. I picked up a book as was suggested and reading it to get additional info.

    If I buy a new camera mega pixels won't be a problem it seems - LOL!

    I guess it'll be a matter of playing around with the settings when I get the camera.
     
  12. SilverUser

    SilverUser TPF Noob!

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    Your post is kind of right and kind of wrong. You make it sound as though the term ISO is just for the digital side. Actually ISO has been used on the film side for decades. ASA was the American standard, but when it went international many decades ago the new term adopted was changed to ISO, so yes both terms mean the same thing and again, the term ISO is not just for digital.
     

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