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11-24-2011, 08:49 AM   #1
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Pentax k100 Asahi 50mm lens

Hi everyone. I am completely new to photography. Other than the spoon fed digital cameras. I recently purchased through ebay 2 each k1000 Asahi 50 mm cameras with various lenses and filters. What I do not have for either camera is a uv filter or polarizing filter. I would like to get 2 sets. I am confused on what to look for to purchase that will fit these cameras.

I have a set of filters that came with my camera and on the lens they say 49 mm. Odd because the lens on the camera says 50 mm.

The ones I have all 49 mm are:

1. center lens
2. diffuser
3. split

Was wondering if you could fill me in on the applicatons these are meant to be used for as well.

Any guidance on the lenses i have and help in locating the correct lenses i wish to purchase will be greatly appreciated.

Cheers!

11-24-2011, 08:57 AM   #2
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Regarding 49mm vs. 50mm i suspect that you are looking at filter diameter (49mm) vs, focal length (50mm). May I suggest that you post what is written on the front of the lenses - which would typically be someting like:

"SMC Pentax-M f/2.0 50mm" or similar.

Do that for all of your various lenses that you got, and we might guide you a bit further. (You might also want to take a look yourself at the lens database and -review sections in this forum).
11-24-2011, 09:04 AM   #3
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The lens in the camera is smc-pentax-m 1:2 50 mm 4759859

Is that what you need to know?
11-24-2011, 10:03 AM   #4
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The 50mm is the focal length of the lens. The 49mm is the filter diameter or the diameter of the threads on the front of the lens. The focal length indicates whether the lens is wide-angle (28mm to 35mm is considered wide on film) or telephoto (greater than 50mm is telephoto). On a 24 x 36mm film camera 50mm is considered to be 'normal' or very close to what the human eye sees.

The filter diameter is what you need to know if you want to screw things onto the front of the lens. Most older Pentax lenses were 49mm with some of the faster ones at 58mm.

The filters you have are:
1) center lens: I assume something that emphasizes the center of the photo area. Possibly blurring the surrounding to look like a frame
2) diffuser: used to 'fog' or blur a picture to give it a moody feel
3) Split: not sure but it could be something that splits the image into two or more

None of these are particulary useful, they would be in the 'gadget' or 'trick' category. And no one would use them today with digital processing as all of the effects can be duplicated (far better) on the computer. If you are new to photography I would put the filters aside, you do not need them.

There is debate on whether a UV filter is of any use, I think it is personal preference although a better case can be made on film than on digital. A circular polarizer is very useful and is in my opinion the only filter you should always have.

Why do you think you need two sets? Usually the filter is just put on the lens you are using if you need it. Remember adding filters reduces both the quality of the image and amount of light passing through so don't use a filter unless the need for it exceeds the penalty from the loss of light.

Post what lenses you got and you will get a better answer about what you need although you need to know what you want to do with those lenses as well. For example buying a macro lens makes no sense if you do not want to do macro photography.

11-24-2011, 10:22 AM   #5
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That lens has a 49mm filter thread, so the filters you have should screw right on the front of the lens. Filter thread size is confusingly unrelated to the lens focal length. Pentax has lenses from 15mm to 200mm focal length that take a 49mm filter.

The filters you have sound like they are all designed for some kind of special effect. You could try just putting them on the lens and seeing how they change the look in the viewfinder. That's what you'd get in a photo. I am guessing based on your description that the center lens one is a doughnut of frosted glass with an open center, used for portraits with a sharp face in the center and dreamy out of focus corners. The effect is sort of like this:



A split filter is meant to produce different effects for the top and bottom of the photo, but there are different kinds. One popular one is neutral gray on the top and clear on the bottom, for sunsets. With this filter, you line up the horizon with the split, and the gray part reduces the sun's brightness, keeping the foreground from being mostly black.
11-24-2011, 11:36 AM   #6
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Lots of good information above.

QuoteOriginally posted by Pdean44 Quote
The lens in the camera is smc-pentax-m 1:2 50 mm 4759859
That's what we call an M50/2, a very common (and somewhat under-rated) kit lens of the 1970s. SMC-PENTAX-M refers to the lens series (M-type). Other numbers indicate the maximum aperture (1:2 or f/2), the focal length (50mm), and the serial number (which might mean it was made in 1975). The lens will work on any modern Pentax dSLR.

Ah, the filters. If you plan to actually shoot film with your new cameras, you will want a UV filter; if shooting B&W film, you'll want a set of B&W filters (yellow, orange, red, green). A polarizer would be handy. Your diffuser and center filters will be useful for portraits.

The split filter could be of several types:

* Split-focus, for apparently extending DOF; half the filter contains a close-up element, the other half is clear glass or empty

* Split-ND (neutral density), for shooting scenes that are half-bright, half-dark (like landscapes under bright skies); half the filter is shaded, half is clear

* Split-contrast, to apply a B&W filter to half the image, like to make clouds stand out without changing a face's qualities; half the filter is colored, half is clear

Split filters and polarizers are useful with digital; the rest are for film only. If shooting color film, color-correction filters may be necessary. I hate those!

We typically don't want to spend a lot of money on multiple sets of different-size filters. Pentax made many many lenses with 49mm front threads just so that only one set of filters would be needed for all lenses. If we have a few lenses with 52-55-58mm threads and more with 49mm threads, we might buy one set of 58mm filters, then use step-up rings to fit them to the narrower lenses. Good filters, especially polarizers, get EXPENSIVE. Ouch. One of each is enough, thanks!
11-24-2011, 12:02 PM   #7
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Here are some specs on your lens:
Pentax-M 50mm F2 Reviews - M Prime Lenses - Pentax Lens Reviews & Lens Database

The one filter that can't always be mimicked in post-processing is a circular polarized, so you could definitely get one of those:
B49CRPLGB Hoya 49mm Circular Polarizer Glass Filter

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11-24-2011, 12:46 PM   #8
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QuoteOriginally posted by Adam Quote
The one filter that can't always be mimicked in post-processing is a circular polarized,
The effects of all the filters mentioned (except the polarizer) can be mimicked when processing digital images. But they may all be needed or at least useful when shooting film. Film development and printing doesn't allow the same sort of control as digital PP. And some film work (chrome ie transparencies ie slides) allows virtually no post-processing at all, so such filters are mandatory -- and a lot of bother!

11-24-2011, 03:35 PM   #9
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QuoteOriginally posted by Adam Quote
...The one filter that can't always be mimicked in post-processing is a circular polarized, so you could definitely get one of those:
B49CRPLGB Hoya 49mm Circular Polarizer Glass Filter
Isn't a circular polarizer pointless on a K1000? It's just a polarizer, except more expensive.
11-24-2011, 10:14 PM   #10
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you folks are awesome ty so much for taking the time to answer my thread.
11-24-2011, 10:17 PM   #11
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Oh i would need two of the lenses so that I can have one and my daughter the other. So looks like the polarizing is the only ones we really need. We both are doing it for a fun father daughter hobby.
11-25-2011, 04:01 AM   #12
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QuoteOriginally posted by Pdean44 Quote
Oh i would need two of the lenses so that I can have one and my daughter the other. So looks like the polarizing is the only ones we really need. We both are doing it for a fun father daughter hobby.
Have fun then - but do take note of Just1MoreDave's note above: Since you will be shooting film only, you don't really need a circular polarizing filter (usually labelled "CPL"). You will do fine with an "old-fashioned" linear polarizing filter with a 49 mm filter thread. You should be able to find these in many places, such as e-Bay for very little money.
11-25-2011, 03:20 PM   #13
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QuoteOriginally posted by Stone G. Quote
You will do fine with an "old-fashioned" linear polarizing filter with a 49 mm filter thread.
Except that if you ever decide to go digital then you will need the CPL. A linear polarizer doesn't play nice with the metering on modern cameras but Stone G. is correct that if you are only using film a linear polarizer is much cheaper.
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