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04-25-2007, 12:36 PM   #1
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Noob questions...! Macro with converter + Pentax-A 50mm f/1.7 ? help

Hello!
this is my first post here, i just bought a k100d

besides the kit lens, this is the first lens i bought, the 50mm works as 75mm on the k100d right?

I'm looking for a cheap macro lenses, the first option i though is buying a 1.4x converter and combine them, with that i'll have a 105mm f/2.4 which i think it could be a good start for macro shots. right?

my first question,
will i have any advantage on using an AF tele-converter with this lenses?

second question,
do you think i should forget the converter and buy a cheap macro lens?
do you recommend any?


sorry if these are noob questions, but this is my first SLR.

thank you all


Last edited by barbosas; 04-25-2007 at 12:57 PM. Reason: new tit
04-25-2007, 04:36 PM   #2
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First, a teleconverter will not allow you to do macros. It will give you more reach. To do macros with your 50mm, you will need either an extension tube, or lens reversing ring. There are a few teleconverters that the internal elements are removeable, turning it into an extension tube, to allow macro photography.

If you really want to do macros, a dedicated macro lens is the best. If you are looking for a good bang for the buck, the Kiron/Lester A Dine/Vivitar 105mm is an excelent lens, IMO as good as any 105mm macro. They can be found quite frequently on ebay for $150-200.

Another option. is one of the 70-300 zooms that do a 1:2 macro, its not a true 1:1 macro, but does a very good job for close-ups of insects, butterflys, flowers, ect...
04-25-2007, 06:44 PM   #3
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QuoteOriginally posted by Pornflake Quote
this is my first post here, i just bought a k100d
Congratulations. Wonderful camera.

QuoteQuote:
besides the kit lens, this is the first lens i bought, the 50mm works as 75mm on the k100d right?
Well, let me try to clarify. Personally, since I'm a good ways from my 35mm film days, I tend to think 50mm = 50mm. Your 50mm lens does what it does, end of story. However, if you are familiar with lenses and focal lengths in the 35mm film world, then you will want to be aware that you will want to do some translating. The lens itself takes in just as much light - and just as wide a view - on a digital SLR as on a film camera. But the sensor on the K100D, the K10D, and many other digital SLRs is smaller than the exposure area in a film SLR. So, on a 35mm camera,

where you would see this much scenery

on a digital SLR with a 1.5x field-of-view (or crop) factor,

where you would see this much scenery

That is, the lens actually throws the same amount of "info" into the camera, but the sensor only captures about two-thirds of it (the part I've put in bold) and throws away the rest (the bits on the right and left that are light gray). Take the two-thirds that's saved and blow it up into a 4x6" print, and you appear to be getting a magnification of 150%. It's okay to think of this as a magnification effect, so long as the image is being captured at high enough resolution for you to be able to print it or view it at the size you want.

In short, if you are used to thinking in terms of the effective field of view of a given lens (say, a 50mm) on a film SLR, then the same lens used on the K100D will seem to have a 1.5x magnification or - more precisely - a 67% "crop" factor. Bottom line: where 50mm was a good "normal" lens for a film SLR, a good normal lens for the K100D will be somewhere between 35mm and 40mm. Where a 300mm focal length on a film SLR was just barely acceptable for shooting wildlife, a 300mm lens on a digital SLR like the K100D is actually pretty good (effectively = a 450mm film SLR lens). And where 28mm is wide angle on the film SLR, on the digital SLR it's a pretty normal focal length and you have to use something around 20mm or less to get a satisfying wide-angle feel in your shots.

By the way, the 1.5x factor on the K100D and the K10D is common on other digital SLRs but not universal. I think my brother-in-law's Canon Rebel XT has a 1.6x factor, and other cameras have different factors. It's all about the physical size (height and width in inches or centimeters) of the sensor, as compared to the normal capture area of 35mm film.


QuoteQuote:
I'm looking for a cheap macro lenses, the first option i though is buying a 1.4x converter and combine them, with that i'll have a 105mm f/2.4 which i think it could be a good start for macro shots. right?
Well, there's macro, then there's "macro", and then there's close-up.

As I understand it, the technical definition of macro is - or at least used to be - that the image is captured on the sensor at 100% of its real size. Using that definition, and using a digital SLR, it's nearly impossible to do macro photography on anything much bigger than a US penny - since the sensor inside the camera isn't much bigger than that. True 1:1 macro photography with film cameras could capture larger objects because the capture area of the 35mm film was larger (see above). And in the past, to do true macro photography, you would usually get your camera very close to the object being photographed.

Now, the term "macro" has been expanded somewhat generously to include capture at ratios of 1:2, all the way up to 1:4 and occasionally even 1:5.

Furthermore, some bright person realized that it may not be necessary to have the lens touching the bug's antennae in order to get a good shot. Lenses with "macro" capability do still differ from "normal" lenses. A normal lens is usually designed with the assumption that you're not going to get closer than a few feet to your subject. A contemporary "macro" lens for a digital SLR on the other hand may permit you to get as close as 12 inches (about 30cm?) or something on that order.

But I've taken some photos I'm rather happy with using a zoom lens from a normal distance. This picture of a bee on a flower was taken with a Canon S3 IS from a distance of 4 feet or so. Not macro photography, really - just "close up" in effect.

QuoteQuote:
do you think i should forget the converter and buy a cheap macro lens? do you recommend any?
Many decent zoom lenses now have a "macro" feature. For example, the Tamron 70-300mm f/4-5.6 Di LD has a 1:2 macro capability. The normal minimum focusing distance is 1.5 meters (almost 5 ft?). Switch to the macro capability and you can shoot at 300mm and get as close as 1.0 meters (less than 4 ft?). Sells for under $200 and has been a quite satisfactory lens for me.

By the way, I bought a Tamron 1.4x teleconverter to use with this 70-300mm lens, for bird photography. Boosts the range from 300mm to 420mm (same zoom effect as a roughly 600mm lens on a film SLR).

Hope this helps.

Will

Last edited by WMBP; 04-27-2007 at 07:24 AM.
04-25-2007, 07:08 PM   #4
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A friend of mine gave me this one for free, because she thought it wasn't worth a dime. I feel bad for her...but not that bad

http://www.keh.com/OnLineStore/ProductDetail.aspx?groupsku=TL060090408820&br...BCL=&GBC=&GCC=

It's a really awesome lens. The focus is precise, the optics are top notch, and it's built like a tank. No, really. It's like 25 lbs of solid brass. It only goes to 1:2, however, so you'd need a 2x teleconverter. Oh, and an adaptall mount, which I hear are becoming very difficult to come by these days.

04-26-2007, 10:14 AM   #5
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thank you for your answers..

i think i'll go for tamron or sigma 70-300, is the sigma non APO a bad choice?
04-26-2007, 10:54 AM   #6
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QuoteOriginally posted by Pornflake Quote
i think i'll go for tamron or sigma 70-300, is the sigma non APO a bad choice?
I haven't used that lens, but no, the non-APO is not a bad choice. It seems to be $100 less than the Sigma 70-300 APO. Both are designed for digital cameras, so that's good. The APO (apochromatic) lens ought to have less purple-fringing or chromatic aberration - but don't let the lack of the APO designation scare you. The non-APO lens is a consumer lens, but it has a consumer price, and I'd be surprised if it is not a perfectly capable lens. I'd suggest buying from a place like Amazon, B&H Photo or (my favorite) Adorama, with a good return policy. Read the policy beforehand, make the purchase, and when you get the lens, test it quickly and treat it carefully, so that, if you decide you don't like it, you can return it in perfect condition.

Here's a link to a page on photo.net where users talk about the Sigma 70-300 APO. Here's a formal review of the same lens on photozone's site. The review is positive but includes some caveats. You have to take all of this info with a big grain of salt. You're not spending thousands of dollars here. The question you should ask yourself is, can I take pictures with this lens that I will be happy with? The lens is not an unimportant part of the photographic process, and there ARE lousy lenses out there. But I would expect that this lens would be decent, and even the APO version is pretty reasonably priced, and the most important part of the photographic process is you, the photographer. And you might find this thread on a Canon forum helpful, as it includes testimonials regarding both the Sigma and the Tamron lenses, as well as more links. The fact that it's a Canon forum doesn't matter to you. You will be buying the same lens, just with a Pentax rather than a Canon mount.

I don't think you can go too badly wrong with any of these lenses. There are bargains to be had buying lenses, and sometimes you will pay too much for something, but generally speaking, there's a correlation between price and quality - but it's not a direct proportionality. As with cameras, when you double your money, you don't get something that is going to be clearly twice as good. So the $200 non-APO Sigma is probably a decent consumer lens; the $300 APO Sigma is surely better, but not a full 50% better. When you get hooked on this stuff, you start to pay lots of money for relatively small improvements in the end-result.

By the way, you might find this info helpful. Tamron has a lot of info about how to buy lenses. There's a "buy Tamron!" slant, of course, but still there is a lot of good info there.

Good luck.

Will
04-26-2007, 04:50 PM   #7
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i should have a panagor 1:1 dedicated macro lens soon. at this time it's in for a CLA. i'll list it in the marketplace when it's available. probably around 105usd shipped.
04-26-2007, 07:22 PM   #8
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Great posts, Will! It certainly helped me a lot, and I'm sure the original poster found it useful as well.

04-27-2007, 02:34 AM   #9
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QuoteOriginally posted by vinzer Quote
Great posts, Will! It certainly helped me a lot, and I'm sure the original poster found it useful as well.

No doubt of it
05-01-2007, 10:12 PM   #10
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hi
look here:https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/6438-macro-lenses-2.html
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