|
Forum: Pentax SLR Lens Discussion
02-16-2014, 11:11 AM
|
| |
Oh, and fretlessdavis: I'd be happy to buy those filters off you and try them out (like you said, I don't have much to lose at $5) but I can't seem to find the thread in the marketplace where you're offering them. If you could direct me to it, that would be awesome of you.
|
|
Forum: Pentax SLR Lens Discussion
02-16-2014, 11:09 AM
|
| |
Thanks for all the advice! Some clarifications:
Yes, the frogs will be anaesthetized. That's why I mentioned that they will stay still for me. Also (I mentioned this in the post too, but it was long so no worries if you missed it) I'm not going to be changing the working distance to match the frog size. Rather than having them fill the frame regardless of size, I want the largest frogs (approx 75mm) to fill the frame, and the smaller frogs to fill a proportionately smaller amount. That is to say, I'll be shooting at the same zoom and working distance regardless of frog size – this is so that I can easily compare relative sizes across images. The camera will be on a tripod with a swing arm that allows it to be held facing downward at the required distance above the ground, and triggered remotely.
Depth of field is indeed important. I'm not expecting the frogs to be razor-sharp all the way down, but I need everything to be at least sharp enough that I can take measurements. The aesthetic quality of the photos is not particularly important, but they need to be distortion-free for accurate measuring and I need to be able to see everything at least relatively clearly.
Does that help narrow down the recommendations? If there is anything else that I can help clarify, please let me know.
|
|
Forum: Pentax SLR Lens Discussion
02-15-2014, 02:37 PM
|
| |
Right now I'm thinking that the DA 18-55mm WR might be exactly what I need. With a maximum magnification of 0.34x, a 75mm long subject will just about barely fit on the sensor, which is perfect. Since I want to take all my photos at the same magnification, I don't need to go larger for the smaller frogs. And I don't need (or want) extreme close up; these are frogs I'm photographing, not insects! The fact that it's a WR lens is attractive as well since I'm going to be using this out in the field where conditions aren't always clean and dry. (Part of the reason I went with Pentax in the first place, since nobody else makes a weather-sealed camera in my price range.)
Does that make sense to y'all? I'm never sure if I'm getting the magnification conversions right, there are always so many factors to worry about. In any case I don't think I need a true macro lens – if I made the image of the frog the same size as the sensor or larger, it wouldn't fit! But a close-up filter might still do the trick, and it would be easier to carry (and cheaper!) than a second lens. What do y'all think about that option? Are there any good close-up filters (or lenses, whatever you want to call them) for the K5?
|
|
Forum: Pentax SLR Lens Discussion
02-15-2014, 01:12 PM
|
| |
Hi. I'm trying to figure out what some good options would be for a macro or close-up lens for my needs. I'm taking specimen photos of small frogs for ecological research, and I need large, crisp, distortion-free images. The subjects are between 25mm and 75mm long, and I would like them to fill the frame as much as possible without any part of the subject getting cropped or distorted; I need to be able to see the whole frog, and I need to be able to take measurements from the photos that are as accurate as possible (there will be a ruler in the frame for measurement calibration). I'm not sure exactly what magnification would work best for me – that's a big part of my question here.
Ideally I would like to focus them all at the same distance and zoom, so that it is easy to compare sizes between individual frogs across photographs. The frogs will sit still for me, and I will probably be photographing them using an external flash and possibly inside a portable light box. I will definitely be using a tripod. I'm shooting a Pentax K5, and my current main lens is the DA 18-135mm WR. Since I'll be in the field and need to carry all of my equipment with me (including all my camping gear and other research equipment) I can't carry a whole lot of lenses. The DA 18-135mm works well for me because it's as close to an "all around" lens as you can get for my budget, I'd be willing to add a macro lens or a close-up lens set to my kit, but swapping out my main lens isn't really an option. My budget is pretty tight as well; I'd prefer not to spend over $150, and less would be better as long as it can fulfill my needs.
Thanks for your advice, I really appreciate it. If there is any important information that I have forgotten to include here, just ask and I'll try to fill you in.
|
