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10-19-2011, 01:40 PM   #1
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pentax k5 ,iso setting and the need for f2.8 lens.

Hi I have been looking at photos on flickr ,with the Tamron SP AF70-200mm F/2.8 Di. selling for 729.00, the pictures are of rc airplanes and helicopters in doors. but what I noticed was the setting were 6500 iso and 4.5 or higher on both settings . never the 2.8. . The other lens is the tamron AF70-300mm F/4-5.6 Di selling for 145.00 . Theres a big price difference in the to lens . So here is my Question , with the high iso setting that the k5 can do , is there any reason that I should pay the big difference to get the f2.8 .now that the high iso setting on the k5 look so clear even with fast moving objects with iso setting over 6500 . I was amazed at how clear the pictures were even at the 12,000 or what ever that other high iso setting was sorry if I didn't put the right number.

10-19-2011, 02:06 PM   #2
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You can compensate light gathering with ISO, but the shallow DOF of a wide aperture and viewfinder brightness are only achieved with faster lenses.
10-19-2011, 02:11 PM   #3
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While I can't say what f-stops I use with when with the Tammy 70-200, I have to say that it's a great lens. My flickr images with it are here:

Flickr: blackcloudbrew's stuff tagged with tamron70200

From my perspective, it's not just that the 70-200 is f2.8, it's that it's constant aperture - f2.8 is available at all zoom lengths. That's why it costs significantly more. The 70-300 can't match that lens speed at any length. From my viewpoint, you always want to keep the ISO of images as low as possible. The fact that the K-5 can shoot at 51,000 ISO is nice but it's not really good there (or honestly anything over 12,000 either). So fast glass is (almost) always a better way to go and ... that has always cost more.

From another perspective, as I recall, a review of the Tammy 70-200 I read indicated that below f4 it tends to be a bit soft, so that's one of the reasons for pumping up the ISO when stopping down.

I've owned an older Tammy 75-300 and own the 70-200, those lenses are not in the same league. That was my opinion with my K10 & K20 too. The K-5 has allowed me to get more out of the 70-200 because of higher ISO ability but it's still a function of good optics not electronics IMHO.
10-19-2011, 02:28 PM   #4
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The 70-200 is about twice as heavy, but produces noticeably superior IQ.

10-19-2011, 02:39 PM   #5
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The tamron works very well for indoor RC shots- here are a few samples: RC Planes - Tamron Gallery - Photography by Adam Oest

They would be even better had I applied some PP noise reduction.

Adam
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10-19-2011, 02:42 PM   #6
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Thank you blackcloundbrew and Matb123, you both take great photos . Ok what about if I wasn't going to use the lens for fast moving thing ,say just for birds and flowers out door stuff building ect would the 70-300 be ok with the k5 . Matt , will you tell me about DOF what it means and its importance in a lens .
10-19-2011, 02:51 PM   #7
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QuoteOriginally posted by pentaxk10duser Quote
Thank you blackcloundbrew and Matb123, you both take great photos . Ok what about if I wasn't going to use the lens for fast moving thing ,say just for birds and flowers out door stuff building ect would the 70-300 be ok with the k5 . Matt , will you tell me about DOF what it means and its importance in a lens .
I probably can't explain Depth Of Field DOF as well as Mat but I'll give it a try. Fast glass like a 2.8 zoom used on that aperture means that a smaller area is in focus and thus (if using a good lens) sharp. If you use it well you can isolate the sharp subject you are shooting from the then blurry background (or foreground). If you stop down the aperture the area in focus becomes greater and your ability to isolate something diminishes. So using a 2.8 zoom (and there are much faster primes) gives you a extra creative instrument.
10-19-2011, 03:03 PM   #8
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Great pictures Adam I noticed that the shots at 2.8 were not as good or as sharp as the ones set at 4.5 . I dont under stand why the 2.8 is so important if the pictures that are taken with 2.8 are not as good . so what if its 2.8 from 70 to 200 . sorry I don't under stand how lens work .I was sure there was a good reason for the price difference but I cant see the difference in the pictures , pictures from both lens with the k5

10-19-2011, 03:25 PM   #9
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In general, f2.8 lenses offer several advantages over 'slower' equivalent zoom lenses:

1) Constant f2.8 aperture means:
- brighter viewfinder for easier focusing
- generally the sharpest aperture settings will be lower, ie f5.6 instead of f8-f11

2) Generally f2.8 lenses have a more professional build quality than cheaper zooms.
- better materials
- better glass
- higher quality internal's

3) Have the ability to isolate your subject with a narrower depth of field. While you may suffer a bit in sharpness, this can be very handy for portraits and other subjects.

4) Allows you to shoot lower ISO's at wider f-stops, should you need to.

4) Bigger lenses make you look like a pro !!!!!

These are general comments, not always the case though, there are some steller performing slower lenses. f2.8's are more expensive, but you need to think of shooting more than just RC planes, buy the lens that is most versatile and the best you can afford, i cant stress that enough because your requirements now might be different to those in a few years time. Good glass is worth the investment, because unlike bodies they hold value fairly well, especially good fast glass.
10-19-2011, 03:35 PM   #10
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QuoteOriginally posted by pentaxk10duser Quote
Thank you blackcloundbrew and Matb123, you both take great photos . Ok what about if I wasn't going to use the lens for fast moving thing ,say just for birds and flowers out door stuff building ect would the 70-300 be ok with the k5 . Matt , will you tell me about DOF what it means and its importance in a lens .
My direct answer to your question here is that, I bought the 70-200 not for fast moving things. In fact some of the best results I've gotten from it have been landscapes (the non-moving ones). It's just got the reach I need for over the fence shots. Clearly I've used it for indoors too but my main reason for getting it was that I wanted a quality, constant aperture lens, with that focal range to upgrade from my other telephoto lenses. The Tammy also is nice for close focusing work too. My other telephoto lens is the Pentax DA 55-300 lens BTW. It's very good too but is not constant aperture or as fast as the Tammy.
10-19-2011, 03:41 PM   #11
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Oh ok Fries , I think I under stand that now . So the only really good thing about having the 2.8 is so you can have the ability to blurry thing around the one spot that is clear. I just got the pretax 100 macro WR . I am a Dental Lab Tech and I am trying to get the best picture I can of all the colors in the teeth so I can duplicate it in the crowns . and I am having trouble figuring out how to get as close as I can but also make the whole tooth be in focus and not just the very center so I have noticed that the higher I make the Number the bigger the area is in focus .is there a point where the higher number like 16 or 22 .is not as sharp as some of the other numbers .I
m still playing around with it but haven't found where its the sharpest ,do I want to just open it up just enough to make the whole tooth sharp and stop there to get the best picture or keep going as high as the light will get me go , what I mean is will 22 give me a sharper picture if I have the light than a lower number
10-19-2011, 04:27 PM   #12
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QuoteOriginally posted by pentaxk10duser Quote
Oh ok Fries , I think I under stand that now . So the only really good thing about having the 2.8 is so you can have the ability to blurry thing around the one spot that is clear. I just got the pretax 100 macro WR . I am a Dental Lab Tech and I am trying to get the best picture I can of all the colors in the teeth so I can duplicate it in the crowns . and I am having trouble figuring out how to get as close as I can but also make the whole tooth be in focus and not just the very center so I have noticed that the higher I make the Number the bigger the area is in focus .is there a point where the higher number like 16 or 22 .is not as sharp as some of the other numbers .I
m still playing around with it but haven't found where its the sharpest ,do I want to just open it up just enough to make the whole tooth sharp and stop there to get the best picture or keep going as high as the light will get me go , what I mean is will 22 give me a sharper picture if I have the light than a lower number
Ossi, great answer and much more complete then I achieved. And to the OP. No F22 doesn't necessarily give you the sharpest photo. I am not the most qualified person to say why; but I'll give it a try. First; you don't need to go all the way to F22 to get a sharp picture in such a small space like somebody's mouth. When you keep stopping your lens down to lets say F22 somewhere along the way the overall sharpness will suffer because of diffraction. Over here there is a explanation of diffraction: Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks. Lenses have a so called 'sweet spot' where the lens performs best. With good lenses you can still shoot very acceptable pictures before you reach that sweet spot and after that 'spot'. It's a good reason not to buy a lot of lenses when you start out using a DSLR. Learn to use the lenses you have before you start a new learning process with a new lens... And if you use F22 your light gathering capability suffers so you have to up you iso and with that the 'noise' in the picture to achieve a proper exposure. And before you know it you'll be using a ring flash to get the picture of those teeth you want.
10-19-2011, 04:57 PM   #13
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Hello Pentaxk10duser,
you mention requirements such as birds (I assume in flight) and flowers. One thing that seems to be left out of the thread is MFD (minimum focusing distance). The Tammy 70-200mm focuses closer than any 300mm zoom I ever used and that plus its top notch sharpness makes it my butterfly and flower lens of choice. Birds on the other hand would require you to be much closer than usually occurs in the wild to use a 200mm without a lot of cropping. The other very nice thing about a fast 200mm is you can drop a teleconverter like the Pentax AF 1.7x on it and have a 340mm/f4.8 equivalent that works well with birds. I use it almost daily.
Enjoy.
10-19-2011, 05:26 PM   #14
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QuoteOriginally posted by pentaxk10duser Quote
Oh ok Fries , I think I under stand that now . So the only really good thing about having the 2.8 is so you can have the ability to blurry thing around the one spot that is clear. I just got the pretax 100 macro WR . I am a Dental Lab Tech and I am trying to get the best picture I can of all the colors in the teeth so I can duplicate it in the crowns . and I am having trouble figuring out how to get as close as I can but also make the whole tooth be in focus and not just the very center so I have noticed that the higher I make the Number the bigger the area is in focus .is there a point where the higher number like 16 or 22 .is not as sharp as some of the other numbers .I
m still playing around with it but haven't found where its the sharpest ,do I want to just open it up just enough to make the whole tooth sharp and stop there to get the best picture or keep going as high as the light will get me go , what I mean is will 22 give me a sharper picture if I have the light than a lower number
I offer this photo of a lens used for this exact purpose, with markings to suggest magnification and aperture for different dental uses:



Lenses are never at their sharpest at the widest aperture. When the aperture is closed a bit, it also starts to limit the most extreme-angle light rays. The ones that get through are traveling in a straighter path. So lenses get better when the aperture is closed a bit. You can see it happening in this lens test, where everything is the same except aperture and shutter speed:




As someone else mentioned, if you have one f2.8 lens and another f4 lens, the f2.8 lens will still look sharper even when both lenses are at f4.5. The f2.8 lens typically has a wider range of apertures where it's very good.
10-19-2011, 07:01 PM   #15
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thank you Ossi and blackcloud , I think I'm getting it now . I'll get 2.8 lens instead of higher number ones like 4,5 and just pay the difference and I'll know i'm getting a better lens, I don't shot rc planes I was just thinking that would be a good test to see what the 70-200 and the 70-300 could do in inside with low light at 200 zoom with the k5 like the ones Adam took . something that was moving very fast inside with low light . I could not think of any thing faster than that .Thank you again fries ,blackcloud ,Thank you Imtheguy and just1moredave , Im going to do that Dave thats a great idea. once i figure out the sweet stop . I'm going to do the reading fries. you all have been a big help . I thought with all the talk about the high iso on the k5 and I figured it would just keep getting higher and clearer that at some point lens would be made in a different way . I can't remember what camera it was but I looked through the view finder and it didn't have mirrors any more it was a digital image through the view finder I think it was a sony . Thanks again for all the help .This forum and the people here are the best.
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