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08-14-2010, 04:35 AM   #1
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500mm vs 300mm

Hi. Sorry if this has been covered but I am out of town and on my mobile phone. There is a 500mm screw mount on fleabay I am watching, and my question is basically this. As far as IQ etc goes is an older 400-500mm lens going to be better than say a DA* 300 with my tamron 1.4 AF TC or even a 2x? I don't shoot anything specific (ie not into birding) but would like to extend the longer end of my range. I currently have the tamron 18-250 and not totally happy with it coupled with the teleconverter. Thanks in advance for any input.

08-14-2010, 04:49 AM   #2
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Depends entirely on the lens. Search here, mflenses,com and manualfocus.org for opinions.

Pretty hard to be worse than the 18-250mm and a TC, though.
08-14-2010, 05:49 AM   #3
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Generally, no. The older long lenses lack the newer lens designs and coatings. This results in poorer contrast, flare resistance and likely reduced sharpness.
Contrast is not a big deal thought, since it is easily adjusted in PP.

They are of course much harder to use being MF and with no aperture level (ie. view finder gets dark when stopped down).
You will need a stable tripod with good ball head to use such behemoths properly.

If you can afford it, the more modern lenses are a better option (ie. A*300; F*, FA*, DA*)

My few cents.
08-14-2010, 06:20 AM   #4
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I had the screwmount SMC Tak 500mm f4.5 and it gave me some nice shots but I'd recommend the DA*300mm & TC: not only is the IQ better (especially with respect to fringing) but the DA*300 is way more portable.

But don't diss the 18-250mm, Euritass,--it's not a serious long lens to be sure but it's a very capable as an "all-rounder."

08-14-2010, 07:36 AM   #5
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Without getting too specific, as this is a purely subjective opinion, I've found that the older telephoto lenses (PK and M42) have produced more pleasing results for me with TCs of the same general era than with the newer PK/A-mount TCs.

I won't offer an argument, or even a theory, for this opinion but I'm comfortable with my experience in this regard. A few years ago I gathered all the older 100-400mm glass hidden in the closet and 12 TCs accumulated over the years and proceded to compare all the combinations.

While there was a wide variety of results, from pretty darn good to abysmal, the general outcome was "older lens plus older TC" was a preferable combination. TC-to-TC and TC-to-lens variations were very noticeable. For instance, of three identical Vivitar M42 2X TCs, one was definitely superior to the other two. In no case were the results of my newer PK/A, AF-capable TCs superior to the older TCs. (YMMV)

My criteria was a comparison between the TC versus the equivalent crop factor which is the only practical argument for a TC anyway IMO. Brand names and original cost had little effect on results.

I also noted that the difference in TCs was often more noticeable in less fringing in the OoF areas than in the apparent sharpness of the in-focus images.

With the price of older M42 and PK TCs so low today, if you want to economically extend the range of your older telephoto lenses I'd recommend accumulating three or four TCs of the same era as the lens and doing your own "shoot-out". You may find a lens/TC pairing that offers surprising performance that's well above your expectations. Or at least within your current budget!

Don't overlook cannibalizing the worst TC by removing the glass to make a sturdy extension ring. That offers a very useful close-focus accessory. A 24-25mm TC shell will cut the minimum focus distance of a typical 300mm lens almost in half and limit max focal distance to less than 200 feet suitable for backyard birding and squirrel shooting.

H2

Last edited by pacerr; 08-14-2010 at 08:58 AM.
08-14-2010, 08:17 AM   #6
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When you get into large, long glass, there are other issues that come into play. First thing is they require a solid tripod. The other is to understand the environment you are shooting in. If for example you are shooting over a lake, swamp, marsh, ocean, there will be atmospheric moisture etc that will effect IQ. Another issue is the sun heating up a large black lens. In cold conditions, condensation be a problem and at night also when shooting moon shots. These are specialty lenses. Those big taks actually make decent telescopes and Pentax even sold an ocular for them and there are 3rd party oculars available as well.
08-14-2010, 10:46 AM   #7
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My observations:

- As Eruditass says, 18-250 + TC probably sets the standard for the worst results you could expect. 18-250 on its own, or even cropped to provide a 500mm equivalent filed of view, isn't so bd, but TC's on consumer zooms are almost always worse than simply cropping.

- 300mm is kind of the dividing line between lenses are possible to make both cheap and pretty and pretty good or else expensive and very good, versus longer focal length where they tend to be cheap and not very good at all or expensive and only pretty good. Size and weight start increasing pretty fast too (except for mirror lenses); 300mm is also about the limit where you'd expect to be able to hand hold the lens reliably. Most people are probably best off stopping at 300mm unless they really have very particular needs and are willing to either compromise or pay (or both) to meet those needs.

- You don't say what kind of 500mm lens you are looking at, but if it's a mirror lens (by far the most common type of 500mm lens), see the Mirror Lens Club thread in this forum for more on them and their specific tradeoffs.
08-14-2010, 11:08 AM   #8
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I always thought the 18-250 was very good in the 135mm and lower areas, but it was not good to work with a TC. A slow lens losing another stop for an f1.4 is even worse :-)

The DA-300 doesn't lose distance with focusing like a zoom lens. never was dissatisfied when using it with my Tamron 1.4 TC. I did find that the difference between a soft picture on a sloping grass surface and a sharp image was hanging weight from the tripod and pushing the feet as hard as i could into the ground. Getting sharp pictures with a long tele is not as easy as other lenses, IMO

best wishes,

08-14-2010, 11:47 AM   #9
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QuoteOriginally posted by philbaum Quote
Getting sharp pictures with a long tele is not as easy as other lenses, IMO.
Amen!
08-14-2010, 12:03 PM   #10
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QuoteOriginally posted by dadipentak Quote
Amen!
That's kind of what I was alluding to in my earlier post.!
08-14-2010, 05:21 PM   #11
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Thanks for the input everyone. I think i will wait and spend the extra to get a good 300mm second hand and just use a tele converter if i want the extra for some reason. I just find i only really use my 18-250 at 250 end and quite often want that little bit more, so i have been considering a decent 300mm for a while now.

It was a 500mm 4.5 Tak that was on ebay and got my attention to answer marc's question.
08-14-2010, 07:42 PM   #12
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Note that the 18-250mm, as with all IF lenses, decrease in focal length as you focus closer. They are only that focal length at infinity.
QuoteOriginally posted by dadipentak Quote

But don't diss the 18-250mm, Euritass,--it's not a serious long lens to be sure but it's a very capable as an "all-rounder."
I have the 18-250mm, and it is an awesome all-rounder and one of my most used lenses. But I don't think anyone would be happy at 250mm f/6.3 with a TC, which is what he was using.
08-14-2010, 08:14 PM   #13
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QuoteOriginally posted by Eruditass Quote
I have the 18-250mm, and it is an awesome all-rounder and one of my most used lenses. But I don't think anyone would be happy at 250mm f/6.3 with a TC, which is what he was using.
I agree completely. I just don't want anyone to get the impression it's a total dog.
08-14-2010, 08:18 PM   #14
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Depends on your needs of course, but here's an illustrated difference between < $100 and > $700 300mm lenses with a 1.4X TC.

The Tamron AF 75-300/4-5.6 LD (672D) at 300mm and f 8 with the Tamron 1.4X PZ-AF MC4. Cropped to 100% and lightly sharpened in Faststone Viewer. That's an effective aperture of f 11 , one stop above actual max aperture. There's a very noticeable softening at f 5.6.



The Tamron Adaptall-2 SP 300/2.8 (360B) at f 4 with the Adaptall 140F TC.
Same PP-ing. Effective aperture f 5.6 here. The image sharpness improves between f 2.8 and f 3.5 actual.




Both off a sandbag rest with the SSLTT (Super Sophisticated Lens Test Target) at about 100 yds. APS-C FL is 600+mm for both.

Here's the normal view through the SP 300 without the TC and before cropping. The holes in the grill are about 2mm in diameter.



With hand held or makeshift support in the field, and under practical circumstances and good light, the economy 70-300mm zooms can produce credible results compared to lenses that cost a LOT more. They're most certainly good training wheels while learning the quirks and special tricks (mentioned above by Blue) that frustrate new tele lens users.

H2
08-15-2010, 10:38 PM   #15
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QuoteOriginally posted by mibane Quote
I just find i only really use my 18-250 at 250 end and quite often want that little bit more, so i have been considering a decent 300mm for a while now.
The difference between 250mm and 300mm is not very significant. I wouldn't spend too much on that 300; I doubt it will get much use. Unless perhaps it happens to be a lens that, unlike the 18-250, works well enough with a TC to be better than simply cropping. In which case you could just kind of leave the TC attached to the 300.

Really, though, if I were you I'd just be cropping more. Doesn't really sound like you have needs that are specialized enough or demanding enough for that not to be a viable (and free!) solution.
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