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04-05-2010, 06:56 PM   #1
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Need help to decide - 28mm f2.8 lens for my K-x

Hi All,

I have a Pentax K-x 18-55 DA L (F3.5 - 5.6) kit lens. I love Macro Photography and when I try with my Kit lens, I am unable to achieve a perfect macro which I am able to achieve with my P.S camera. ( I did a close up shot of a flower with my Kit and my canon P.S and the snap of my Digi was far more better than my SLR.)

I wanted to buy a lens with f2.8 and cannot spend a fortune on it. I searched in ebay and found a used lens "SMC Pentax M 28mm f2.8 1:2.8 SLR Camera Lens" for about $90.

1) Is it worth buying a old lens for this price?.
2) Can I get good Macro Shots with this?. And will this be useful for Portrait shots too?.
3) Will this fit my K-x or should I use any other adapter to fit my camera?.

Please help me decide. I have a very limited knowledge and I would like to have the xperts advice on this.

Thanks
Srini

04-05-2010, 07:16 PM   #2
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One reason P&S digital cameras are great at close-up shots is their small sensors. At the same f-stop, they have a lot more depth of field (part of the photo that's in focus) than on your K-x. Their lenses can be smaller and optimized for closeup.

To get better depth of field with the K-x, you need to use at least f11, maybe higher if you are close to the minimum distance that the lens can focus at. The lens that came with the camera is a better choice for that, because it can focus a bit closer and allows you to use f-stops higher than f22. I would try to get that to work before buying another lens for this purpose. You may need lots of light, a high ISO setting and/or a high f-stop number to match the P&S if you're really close.

For other purposes, the Pentax-M 28mm f2.8 lens is pretty good. It will mount without an adapter and work in M mode with stop-down metering. See the sticky atthe top of the beginner's section for how that works.
04-05-2010, 07:22 PM   #3
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The M28/2.8 is a fine lens, but it's not a macro lens - it won't get nearly as close up ads the lens you already have. Being f/2.8 has nothing to do with being macro - in fact, you usually don't want f/2.8 when shooting macro. You haven't said what in particular you are unsai=tisfied with using the 18-55, but I'm guessing Just1MoreDave is right above when he suggests the problem is that you are not used to how shallow the DOF is with a DSLR. And in that case, f/2.8 is the *last* thing you want - it will make DOF shallower still. You might try posting pictures that show what you are unhappy with.

Also, 28mm is not really a good focal length for portraits - unless you like your 18-55 set at 28mm. The M28/2.8 is indeed somewhat sharper, but it sounds like you roabbly need to find a good book on photography to learn the basic concepts of depth of field and focal length.
04-05-2010, 09:55 PM   #4
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Tamron SP AF 90mm f/2.8 Di Macro

My first macro was the Tamron SP AF 90mm f/2.8 Di Macro. It's a popular choice because it's a great portrait lens and a good value. You may be able to find a used one for $300. It's also a different focal length than your kit lens.
That may seem like a lot of money, but you'll appreciate the auto-focus on a lens longer than 50mm, and AF lenses tend to be more expensive.

04-05-2010, 10:05 PM   #5
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a cheap alternative for macro would be buying a close-up diopter lens like the Marumi which you could stack up at the front of your kitlens for Macro work. the kitlens is actually very good when it comes such photography use. fix at the 35mm where the lens is at it's best and just like what the other posters suggested, close down your aperture to a minimum (f8 to f11) and have enough lighting (whether use a flash, bump up your ISO or decrease your shutter speed). as far as which Marumi close up lens to choose, a +3 and over would work well on the kit lens. I think you could buy one for $50 bucks.
04-06-2010, 12:40 AM   #6
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Depending on how you wish to shoot, and how close and with what magnification, you have various options. If using a flash, the easy way is to use a Marumi or Raynox or other quality closeup adapter. But those those don't get you to 1:1 magnification. If using available or set light, you can use a prime lens and bellows (flexible) or extension tubes (cheap).

The right lens depends on where you're shooting -- in studio, or in the field? Many like a good cheap manual 50mm lens on tubes, like the Industar-50, for studio work. In the field you want to be further away, so ~100mm macro lenses are popular. A cheap setup for field work is a ubiquitous 135mm manual lens on tubes. For macro work, expensive fast AF lenses are irrelevant. You could put together a package of I-50, 135, and tubes, for US$50-100 with no sweat. Then you need only practice, practice, practice. Have fun.
04-06-2010, 07:01 AM   #7
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I have gotten good results with the 18-55 kit lens and a Hoya +4 closeup filter. Amazon has the 3 filter set for ~$40. You could pay a little more and get the Raynox 250 snap-on closeup filter, if I had known this existed, I probably would have gotten one instead of the Hoya set.
04-06-2010, 07:36 AM   #8
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QuoteOriginally posted by srini Quote
1) Is it worth buying a old lens for this price?.
2) Can I get good Macro Shots with this?. And will this be useful for Portrait shots too?.
3) Will this fit my K-x or should I use any other adapter to fit my camera?.
My thoughts:

1) Yes if the lens is in excellent condition.
2) Probably not due to the wide focal length and relatively long minimum focusing distance. Also, the 28/2.8 can be used for portraits but not necessarily traditional shots. The wide focal length can result in exaggerated facial features even when used on a crop-sensor DSLR.
3) A Pentax 28/2.8 with the bayonet twist and lock mount should fit on a K-x.

I suggest a true macro lens such as the Pentax 50/4 Macro. The big used retailer I shop (KEH) has an M50/4 in EX condition listed for $94 plus shipping. Even better would be the Pentax 100/4 Macro but it's more expensive.

04-06-2010, 09:14 AM   #9
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If you want a nice closeup wideangle and don't want to break the bank, look for any of the Vivitar 28mm f/2.8 Close Focus variants made by Komine (look for a serial number starting with 28).

These are an incredible value, and unfathomably sharp.

You can get more info here: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/56451-great-vi...-bestiary.html
04-06-2010, 11:44 AM   #10
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I also have the M 28mm 2.8 and i believe it is a great walk around middle range lens. However, as stated already, it is not a macro lens. The Tamron 90mm is a great choice if you want to spend on a macro lens. If you have the money, the pentax 100mm wr is the way to go, but the tamron does 95% of what the pentax does, at 1/2 the cost.
04-06-2010, 08:44 PM   #11
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QuoteQuote:
You might try posting pictures that show what you are unhappy with.
HI Marc,

You are right, I did not understand the basics properly. But pls take a look at the pics below and correct me.
Also the Basics and focal length and F-stops available in Wikipedia is way above my head. Is there any simple docs/links which can explain it in more simple words?. If yes, please do share with me.

The first one was taken with my P&S and the Second one with my Kit lens (55mm,F5.6, Auto ISO).

Thanks
Srini
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04-06-2010, 09:47 PM   #12
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QuoteOriginally posted by srini Quote
HI Marc,

You are right, I did not understand the basics properly. But pls take a look at the pics below and correct me.
Also the Basics and focal length and F-stops available in Wikipedia is way above my head. Is there any simple docs/links which can explain it in more simple words?. If yes, please do share with me.

The first one was taken with my P&S and the Second one with my Kit lens (55mm,F5.6, Auto ISO).

Thanks
Srini
hello Srini, you also need to consider angle inorder to get the focus nicely on the flower. 1st picture looks off (half the flower and the background are in focus. 2nd picture shows the flower completely in focus and totally isolated from the background. I would advice you to shoot at 35mm rather than at 55mm. the kitlens is soft at 55mm.
04-07-2010, 08:25 AM   #13
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QuoteOriginally posted by srini Quote
Also the Basics and focal length and F-stops available in Wikipedia is way above my head. Is there any simple docs/links which can explain it in more simple words?
Check this link out, it talks mainly about exposure (metering) but also covers the basics on f-stops, shutter speeds, ISO, EV, etc.

Ultimate Exposure Computer
04-07-2010, 10:47 AM   #14
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Srini, both of your shots look pretty good. I've been amazed by the quality of some of the close-up shots I've taken with point-and-shoot cameras. Your second photo looks about right compared to what I've be able to do with my 18-55 under similar conditions. Both of your shots include well lit backgrounds which tend to highlight the out of focus effects or feel of your lenses when shooting close-up. Also, as your lens to subject distance decreases with close-up shots the depth of field also decreases resulting in a greater need to stop down the aperture to a larger F-number to get more depth of image in focus.

I'd suggest you keep experimenting to see what you like. Most of the fantastic pro macro shots you see are taken using not only high grade macro lenses but also flashes and tripods intended for macro work. In other words, it's a whole new obsession.
04-07-2010, 11:42 AM   #15
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To begin with, the lens on your P&S is probably something like a 6-10 mm lens in reality. Even point and shoot cameras have crop factors. Wide angle lenses have a DOF of approximately infinity and allow you to focus very close to your subject. Your best bet, if you don't want to go broke on a dedicated macro lens, is to use a closeup attachment on your lens. If you can find one at a less than rape the buyer price a Nikon 5t or equivalent (I have a Minolta version) which I believe is a 52mm thread, should mate up to your 18-55 kit lens nicely. These, in my general experience, are quite useful on zoom lenses in particular for closeup work. I have a 6t that I put on my Tamron zoom once in awhile.

I'm not saying the M28 is not a nice lens but for Macro work, less expensive and more useful options are out there. The 28mm does make a nice walk around street photography lens. My 2, take it for what you think it's worth.

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