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05-29-2011, 08:16 AM   #1
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Getting new zoom and lens redundancy

I just ordered the Tamron 17-50mm f2.8 and am waiting for it to arrive. In the meantime, I was just wondering about other pieces of glass and if they'd be made redundant by the new one. The lenses I own and think might become redudant are:

DA 18-55mm WR. I haven't really shot in very extreme conditions, but have used the lens in either light rain or snow and not having used any non-WR lens in these conditions I was wondering if it is something they can stand... in this case if the Tammy can be used in light rain/snow or in a beach with some wind.

FA 28mm f2.8. My guess is that this one will be sharper wide open than the Tammy at 28mm, but is it a lot sharper? Does someone who owns or has owned these 2 made any comparisons?

DA 40mm f2.8. Same as the 28mm although I will always love this one for giving such a low profile to my camera

Thanks!


Last edited by betamax; 05-29-2011 at 08:56 AM.
05-29-2011, 08:51 AM   #2
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The 17-50mm is very sharp. Even wide open it still has good sharpness. I owned it briefly and was particularly impressed by the sharpness. If you're looking at the primes primarily for a sharpness advantage, I wouldn't bother.

As far as the 18-55mm WR....if you rarely shoot in wet conditions, I would probably just hold onto your 18-55mm kit lens and put your money towards more creative glass. Maybe your kits lens will hold up okay in moderate weather as long as you're careful, and if not, then you're only out $50 and can maybe then decide if you need the WR. And you didn't mention what body you have, but if you don't have a weather-sealed body then a WR lens will only take you so far.

You should be aware that the Tammy 17-50mm may not be a true f/2.8 lens. My experience is that it actually only has a max aperture of f/3.3 or f/3.4. If you do end up getting one of the other lenses you mentioned, you may find that they are brighter at f/2.8. I ended up returning my 17-50mm for this reason.

If you're wanting to get a fast zoom and a compact prime, you may be better off with the combination of the Tamron 28-75mm f/2.8, and the Pentax 15mm limited. The 28-75mm has outstanding image quality (and is a true f/2.8), and I find the 28-75mm range much more useful when taking pictures of people. And the 15mm would give you a top-quality wide angle in a very small package.

Be sure to check out my Tamron 28-75mm thread for lots of sample pics from this lens:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/145599-tamron-...lots-pics.html

And of course, there's the 15mm ltd controls my mind thread, 146 pages and counting:

https://www.pentaxforums.com/forums/lens-clubs/86234-15mm-limited-controls-my-mind-club.html

And if you're curious about the max-aperture problems with the 17-50mm, check this thread out:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/124013-tamron-...-k-x-pics.html

Last edited by Edgar_in_Indy; 05-29-2011 at 08:58 AM.
05-29-2011, 08:56 AM   #3
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Probably should have explained better. I already have the other 3 lenses and was wondering if the Tammy would leave them collecting dust (well, the Kit and the 28mm mostly, I love that 40mm).

And by "not true 2.8" do you mean that the camera will meter it as a 2.8 but will work as a 3.3? Would that result in underexposed shots?

Edit: Also I decided to go for the 17-50 instead of the 28-75 because I noticed I was taking shots in the wider end of the kit lens when I used it that would not be covered in the 28-75. I am planning to acquire an FA 77 for portraits soon though, which is what I read that the longer end of the 28-75 is mostly used for. Although that thread is giving me second thoughts now...

Last edited by betamax; 05-29-2011 at 09:03 AM.
05-29-2011, 09:05 AM   #4
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My guess is either the FA35 or DA40 FA35 will mostly collect dust, but one will continue to get use just because they are so much smaller. Note the FA35 is f/2, not f/2.8, so that might get the nod for that reason, but the DA40 is smaller and focuses even faster, so either might seem the small alternative to the 17-50 you'll occasionally want.

The 18-55 will seem tempting on rainy days, although yes of course you can use a non-WR lens too - just keep it reasonably well protected.

05-29-2011, 09:12 AM   #5
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QuoteOriginally posted by betamax Quote
And by "not true 2.8" do you mean that the camera will meter it as a 2.8 but will work as a 3.3? Would that result in underexposed shots?
I only shoot full-manual, so I unfortunately I can't comment on whether the metering was accurate. But I've seen other people talking about having to use exposure compensation for the 17-50mm to prevent underexposure.

It showed f/2.8 on my camera, but when compared to f/2.8 shot with my other f/2.8 lenses (Tamron 28-75mm, Sigma 50-150mm), the 17-50mm was darker, telling me that it was letting in less light.

I did extensive controlled testing, and discovered that the 17-50mm at f/2.8 was equivalent to my other lenses at f/3.3 or f/3.4 in terms of exposure. So basically I was losing half an f-stop with the 17-50mm when shot full-open. When stopped down below f/7.3 or so, the difference was almost a full stop. This was true even when comparing to the Pentax kit lens.

I suggest you do the same comparisons when you get your copy. If yours exhibits the same behavior, and having true f/2.8 is important to you, then you may want to think about doing like I did and return it before the return period ends.

Based on what I've read online, I don't believe the new Tamron 17-50mm VC suffers from this problem, nor does the new Sigma 17-50mm OS.

Last edited by Edgar_in_Indy; 05-29-2011 at 11:11 AM.
05-29-2011, 11:58 AM   #6
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QuoteOriginally posted by Edgar_in_Indy Quote

I did extensive controlled testing, and discovered that the 17-50mm at f/2.8 was equivalent to my other lenses at f/3.3 or f/3.4 in terms of exposure.
With more elements and inferior glass, you'll get lower light transmission and t-stop. lenstip.com is one of the few sites that tests this.

Nikon Nikkor AF-S 24-70 mm f/2.8G ED review - Ghosting, flares and transmission - Lenstip.com

They haven't tested the sigma 17-50 for this though.

EDIT: Compare that to Pentax DA 35 f/2.4:
http://www.lenstip.com/299.9-Lens_review-Pentax_smc_DA_35_mm_f_2.4_AL_Ghosti...nsmission.html

Last edited by asdf; 05-29-2011 at 12:08 PM.
05-29-2011, 12:20 PM   #7
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QuoteOriginally posted by asdf Quote
With more elements and inferior glass, you'll get lower light transmission and t-stop. lenstip.com is one of the few sites that tests this.

Nikon Nikkor AF-S 24-70 mm f/2.8G ED review - Ghosting, flares and transmission - Lenstip.com

They haven't tested the sigma 17-50 for this though.

EDIT: Compare that to Pentax DA 35 f/2.4:
Pentax smc DA 35 mm f/2.4 AL review - Ghosting, flares and transmission - Lenstip.com
Several people have mentioned t-stop to me, and I'm aware of this. But I've compared all of my lenses, from a cheap Quantaray 28-80mm to the Pentax 18-55mm and 55-300mm, all the way to my $800 Sigma 50-150mm f/2.8, and all of the lenses expose pretty much identically at any given aperture, with just tiny, tiny differences (I attribute those almost imperceptible differences to the difference in light transmission). All of them except the Tamron 17-50mm f/2.8, which is drastically different. So I don't think it's just a matter of a minor difference in light transmission.

On the other hand, if it is the case that light has such a hard time penetrating the elements of such a popular lens, I think that would be an even more startling deficiency than an aperture error. But given how good the glass in this lens seems to otherwise be, I have a hard time believing that to be the case.

Last edited by Edgar_in_Indy; 05-29-2011 at 12:25 PM.
06-01-2011, 02:24 AM   #8
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I am still waiting for the Tamron to arrive. The Post Office might be going on strike tomorrow here in Canada so if it doesn't arrive today I might be waiting for a while more.

With 6 years of manuf. warranty I think the AF issues might become annoying if they happen but not worry me that much. The underexposure problem would be fixed if I compensate for it, though, right? See +0.5/+1 EV if I am shooting on aperture priority?

QuoteOriginally posted by Marc Sabatella Quote
My guess is either the FA35 or DA40 FA35 will mostly collect dust, but one will continue to get use just because they are so much smaller. Note the FA35 is f/2, not f/2.8, so that might get the nod for that reason, but the DA40 is smaller and focuses even faster, so either might seem the small alternative to the 17-50 you'll occasionally want.

The 18-55 will seem tempting on rainy days, although yes of course you can use a non-WR lens too - just keep it reasonably well protected.
It's the FA 28, not 35. I am selling that one anyway, and putting the money towards something I could use for portraits. Thinking right now the FA 77.

06-01-2011, 03:19 AM   #9
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QuoteOriginally posted by betamax Quote
Thinking right now the FA 77.
Yes, you're thinking right (now ;~)
06-01-2011, 05:31 AM   #10
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QuoteOriginally posted by betamax Quote
The underexposure problem would be fixed if I compensate for it, though, right? See +0.5/+1 EV if I am shooting on aperture priority?
If the lens is really only opening to f/3.3 or f/3.4 as I suspect my copy was, instead of f/2.8, then no amount of exposure compensation will fix that. The only thing that exposure compensation will do is tell the camera to automatically decrease the shutter speed to compensate for the smaller aperture.

But you'll still be missing out on the advatanges of f/2.8. Those advantages include 1) a more shallow DOF allowing more seperation between your subject and the backround, and 2) Being able to shoot at a faster shutter speed. This helps to reduce blur caused by subject motion and/or camera shake. One of the main causes (perhaps the main cause) of soft photos is using too slow of a shutter speed.

So yes, using exposure compensation will allow you to get properly exposed photos, but you will still be left with backgrounds that are less blurred and will have to deal with slower shutter speeds. I wasn't willing to make those sacrifices so I returned mine.

Last edited by Edgar_in_Indy; 06-02-2011 at 07:00 AM.
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