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04-18-2010, 05:56 AM   #1
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How much of a difference between 2.8 and 3.5

I have somewhat of a dilemma now. I have two 135mm prime lenses. One a no name Beck and another Takumar one. Now I find the Takumar produces sharper and more vibrant colours compared to the Beck one. However, my real question is how much of a difference will there be between a F2.8 (Beck) and F3.5 (Takumar)? I have I will have DOF difference with the Beck being shallower. However will the F2.8 be that much better in low light conditions? It seems to me that it is less than 1 stop and that could easily be fixed with ISO or shutter speed.

Thanks for the insight and comments

04-18-2010, 05:59 AM   #2
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2/3 stop........................
04-18-2010, 06:42 AM   #3
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there won't be much difference in DOF either...if I were you I would stick to the takumar...there are alot of users here that love that lens, and use it in low light.
04-18-2010, 06:49 AM   #4
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as Cosmo pointed out it's 2/3 of stop.

Now that means shooting at ISO 640 instead of 400 or 1250 insted of 800 or accept 2/3 of stop less in shutter speed if you don't want to bump the ISO up. This affects 2 things: 1- motion blur as speed produced by f3.5 at acceptable ISO (to you of course) may not be fast enough to freeze the motion. 2-lens/camera shake blur, where again the shutter speed you get may not bee fast enough to prevent shake blur.
Minnd you in dim light 2/3 of stop can make huge difference with 135mm. While f2.8 would give you lets say 1/125 shutter speed f3.5 in thee same conditions and settings would only produce 1/80 which at 135mm is notablee difference.

oh and one more thing. When trying M135/3.5 I found out that f3.5 is just dark enough to render micro prism collar of my focusing screen nearly useles...while not the best, it's still usable at f2.8

04-18-2010, 07:17 AM   #5
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A tricky question. Two different lenses, probably with two entirely different optical formula, both at wide open . . . . .


I think we need sample pics to tell you, really.
04-18-2010, 08:39 AM   #6
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You said it yourself.....a "no-name" Beck (I've never heard of it) and a "Takumar"....still loved, respected, used and coveted around the world almost four decades after they went out of production.

Does the f2.8 and f3.5 bit really even enter into the question?

But just for the technical bit, the difference between f2.8 and f4 is one stop, so f3.5 is less than one stop difference. Not enough to be a factor in making a choice.
04-18-2010, 08:50 AM   #7
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In terms of stops it is about 1/2 to 2/3 but this means 50 to 60% increase in shutter speed wide open. while SR and high iso can help some, freezingthe subject needs shutter speed.
04-18-2010, 08:57 AM   #8
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sell both and buy a takumar 135 2.5

04-18-2010, 11:18 AM   #9
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Really I don't think that there is much of a difference. I mean your shutter speed is going to change and you depth of field might increase slightly, but not by much. If I were you I would sell both and pick up the takumar 135 f/2.5 myself, it really is a great lens to use.
04-18-2010, 02:49 PM   #10
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As mentioned above, the fractional f-stop difference is trivial except in low light, when it's minor. The Takumar is worth far more, produces better results, etc. The no-name Beck can be useful if you're shooting in hazardous places and you don't care if the lens is damaged or trashed. If the f-stop difference were greater, if the Beck were a f/2 for instance, then it would be worth keeping for situations where speed is more important than image quality, like blackmail.

But it all depends on what you want to shoot, and from how far away, and what else you want the lens to do, if anything. Sell both and buy a Takumar 135/2.5, or almost any 100/2.8 or f/2 macro, or...

It depends on the light you shoot in. For low-light, faster is better. For daylight, slower is often sharper. My GOLD STANDARDS in that range are an Enna Tele-Ennalyt 135/3.5 and especially the Jupiter-11 135/4, both with astounding optics. (Less than US$90 for the pair.) Some people rob minimarts to pay for a 200/2.8 beast; my light little Tele-Takumar 200/5.6 cost US$29 and is tack-sharp throughout its range. And 'pods are handy.

So it's all a matter of where you shoot and when and how hazardously, and how much glass you want to carry, and how much cash you want to drop, etc. I'll repeat my mantra -- Ask yourself: Where do I want to go? What will get me there? How much am I willing to spend to be happy?
04-18-2010, 02:55 PM   #11
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Note that while mathematially, f/3.5 might be 2/3 of a stop slower, the actual labeling of the stops is rarely mathematically correct. On lenses that can do f/2.8 or better, f/3.5 is simply how Pentax labels the half stop between 2.8 and 4. So I wouldn't assume a lens that is labeled f/3.5 is actually any more than half a stop slower.

I have the M135/3.5 and use it all the time in low light (for concerts, primarily). While sure, I wouldn't mind if it were half a stop faster, that's *trivial* to make up in shutter speed and/or ISO, and it's so much smaller and lighter than any of the f/2.8 lenses that I'm really not overly tempted by them. The Takumar probably doesn't have that going for it, of course, but if you find it a better lens, that's all that matters.
04-18-2010, 03:42 PM   #12
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Another difference is 10mm in aperture. That 10mm will give you a greater possible blur of background.
04-19-2010, 12:43 AM   #13
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Forget about the difference in speed, keep the Takumar.
To sell both and get a K135mm F2.5 is not a bad idea if you can cope with its size.

Kind regards
.lars
04-19-2010, 09:26 PM   #14
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I would love to buy a 2.5 but they aren't easy to come by and I'm guessing they aren't that cheap. I will post some sample pictures from the two lenses in a couple of days. But I'm probably going to sell the Beck along with my film camera body. Could probably be easier to sell them as a package then separately. Thanks all for the help for now.
04-19-2010, 10:20 PM   #15
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I think the best 135mm f3.5 option is the Pentax-M. Depending on what Takumar version you have, you can possibly sell the Takumar and get the Pentax-M for the same price. The Pentax-M is a much more convenient size.

For f2.8 and a small budget, I still like the Vivitar made by Komine. These are very cheap and common. You can find one of these for less than $30 shipped.

The SMC Pentax 135mm f2.5 is really a great lens. The extra speed may not be worth the extra cost, and it is bigger. The Super-Multi-Coated Takumar 135mm f2.5 model 43812 is the same formula and is actually a bit lighter. Model 43802 or Super-Takumar f2.5 versions are not far behind in quality and are sometimes sold at decent prices.

The Takumar Bayonet 135mm f2.5 is not a bad lens if you can find one for $20. At $75, it's a bad lens.
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