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03-03-2011, 02:27 PM   #1
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"Good" lens question

So I've been wondering lately...
I've never owned a really good (expensive) lens, just kit lenses, a m50 1.4 and a canon 50 1.8 when I had my t1i. Currently I have a K-r with 18-55,50-200 kit lens (and the m50). My question is this: If I were to use either of my kit lens and shoot in fairly optimal conditions, would there be a big difference in image quality if I were to shoot the exact same scene with a "good" lens? I've seen these kinds of tests, but the subject matter was one of those indoor studio test shots with random colorful objects which did not clear up my confusion.

(as i read this back, the question seems silly to ask. maybe i'm just asking for real world examples of the same scene shot with the kit lens and something "better".)

03-03-2011, 02:40 PM   #2
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Could be a significant difference, depending on your standards, the aperture used, and in the case of the zooms, the focal length. (And how accurate your manual focusing,)


The kit lens with Pentax is nice as kit lenses go, and has some good sweet spots around the moderate focal lengths and apertures.
03-03-2011, 02:56 PM   #3
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I think it's also fair to say, how big are your making your images, either screen or print and also at what viewing distance will you be looking at them, pixel peeping does no good.

It boils down really to what is acceptable to you.
03-03-2011, 03:00 PM - 1 Like   #4
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You have the DA 18-55 and the M50/1.4, try it yourself. Tip: let the camera meter with the DA, then copy the settings when you use the M.

The DA 18-55 is pretty good away from its extremes. Those can be either end of the zoom, wide open, or sharpness and contrast at the edges/corners instead of the center. I have a couple of decent 28mm prime lenses. Compared to the DA at 28mm, the primes are infinitely better at f3.5 or wider, because the kit only goes to f4. At f4, the primes are noticeably better if you are looking for it. At f8, you have to look very hard. In the center of the shot, they are even.

At 50mm, the M50/1.4 should be a lot better than the DA. It is four stops faster, a really huge difference. That helps when you stop both lenses down to f8 - the kit lens is just one stop from wide open, the M is five stops down.

The next question might be, is it worth it for me to spend more and get a good lens? That gets tricky. It helps a lot to define your needs before looking beyond the kit lens. Good lenses are designed for a purpose, so a good lens is worth more to you if that's your purpose, and worth-less if you don't need it.

03-03-2011, 03:40 PM   #5
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One of the deciding factors for me was having a fast zoom lens (f2.8 or so) with a constant aperture. As these tend to be more expensive and also tend to provide better image quality. While the Pentax kit lenses offer good results, they just don't measure up to the more expensive stuff all round. You really do generally get what you pay for in lenses.

The other commentors make a number of good points. When you do decide to upgrade, do it with some thought and some need in mind that getting better glass would address. Honestly, the next lens you buy (and you will succumb to LBA as we all eventually do), will say a lot about the kind of photography you want to do. Personally, I can say that when I replaced my kit lens with my DA*16-50 f2.8 lens, I got it right then what a good lens can do for you.
03-03-2011, 03:42 PM   #6
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Dave, so let's say I have to rely on my 18-55--and want to treat it as a prime:

What FL and aperture is going to give me the best IQ, forgetting about DOF issues? This is the only AF lens I own, and I recently had a not great experience trying to shoot a low light party with manual lenses, and focus was a disaster.

If I know the sweet spot for this lens, I'll leave it there next time...shoot like it's a prime...and adjust my manual flash to make it all work with the camera in M mode.
03-03-2011, 04:03 PM - 1 Like   #7
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You have the 50 1.4. If you're using it right you've already seen what a "good" lens can do.
Also, primes often best zooms in IQ, or at least they used to, and 50mms are especially good in respect to corrections and optical design, because 50 and 55mm lenses were the standard for so long. Years and years of experience have made 50 and 55mms very refined and well understood optically.
I can't speak too much on zooms, which are a whole different ballpark, but even 50 year old third party primes tend to be decent, so newer Pentax primes should be SUPERB. Maybe not as convenient as zooms, but older (still very good) primes can often be had for very very little. Newer primes, especially from Carl Zeiss, Pentax, and Canikon are often more expensive, but not as expensive as zooms of comparable quality and aperture.
03-03-2011, 04:07 PM   #8
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Where 'better' lenses are better are in speed (maximum aperture), and sharpness and IQ at speed. Fast wide-normal (24/2, 35/2) lenses will shoot faster (for low light, or moving subjects) than the 18-55, and will likely look better up to f/8. Ditto with fast longer lenses (85/2, 135/2.5, 200/3.5) than the 50-200. And a faster lens gives you thinner, more controllable DOF.

Some not-so-speedy, not-so-pricey Pentax lenses (28/2.8, 35/3.5, 105/2.8, 135/3.5, 200/5.6) may look a bit sharper from wide-open on up. I don't have anything 'better' than Pentax Takumar and M-class primes, not counting some Nikkor and Zeiss and Schneider glass, so I can't comment on Ltd's and *'s and the like. But good primes just give a different experience, and strange primes may lend a distinct character, than you'll get with the kit lenses.

I am a sucker for cheap old manual primes, and enlarger lenses on bellows, and all that stuff. After my original set of K20D + DA10-17 + DA18-55 + FA50/1.4, I bought the DA18-55 and use it for certain purposes. But I've also bought many scores of manual primes, and enlarger and projector lenses, and whatever weird optics may jump out at me. Variety is spicy, yup.

03-03-2011, 04:08 PM - 1 Like   #9
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Better lenses tend to produce good results under a wider range of circumstances than cheaper lenses.
03-03-2011, 04:18 PM   #10
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I agree with most posts made so far.
1) If you do not intend to make a lot of large scale prints than the little extra sharpness of 'good lenses' won't add much to your images.

2)
QuoteOriginally posted by blackcloudbrew Quote
One of the deciding factors for me was having a fast zoom lens (f2.8 or so) with a constant aperture.
Me too I would say that this is the issue that at least I really miss about the normal kit lens! Having a fast zoom (or fast primes) gives you a lot of extra possibilities for shooting...

3)
QuoteOriginally posted by PGillin Quote
You have the 50 1.4. If you're using it right you've already seen what a "good" lens can do.
Image wise I think you already have a good lens with your M-50mm. Only not the most convenient one regarding the missing 'A' setting (and possibly AF).


Finally (to contradict my own post)... I can't deny that having a nice new lens can be a very motivating factor...
03-03-2011, 04:26 PM - 1 Like   #11
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About the only time it would be hard to spot the difference would be outside on a sunny day shooting at f8+. I think about 5% of my pictures are like that. Otherwise a "good" lens will give superior results. Some times there is no other way to even get a sharp photo without a good lens (think indoor sports).

I completely disagree about only being able to spot the difference at large print sizes or pixel peeping. Good lens produce pictures that are different (in a good way) even in very small sizes. A FA31 indoor image shot wide open for instance can be spotted as better than the kit lens even at tiny display sizes.

By the way, the M 50mm 1.4 is a good lens. If you can't see the IQ difference then maybe for you isn't isn't worth buying more good lenses.

Last edited by twitch; 03-03-2011 at 04:35 PM.
03-03-2011, 04:32 PM - 1 Like   #12
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You Have a good lens. I suspect you just aren't making use of it though (unless you define good differently than I do)... The M50 f1:1.4 is probably one of the best in that range you'll find. The best part of it is, since you already have it, you don't have the pay the current ridiculous asking price for it..

Pentax 50mm f1:1.4 - a set on Flickr

I don't have any side by side tests with it though but I will say that (IMO), it makes the kit lens (18-55) look terrible, at 50mm.

03-03-2011, 04:38 PM   #13
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QuoteOriginally posted by SpecialK Quote
Better lenses tend to produce good results under a wider range of circumstances than cheaper lenses.
This makes sense... thanks for wording it that way.


QuoteOriginally posted by PGillin Quote
You have the 50 1.4. If you're using it right you've already seen what a "good" lens can do.

QuoteOriginally posted by Just1MoreDave Quote
You have the DA 18-55 and the M50/1.4, try it yourself. Tip: let the camera meter with the DA, then copy the settings when you use the M.

The DA 18-55 is pretty good away from its extremes. Those can be either end of the zoom, wide open, or sharpness and contrast at the edges/corners instead of the center. I have a couple of decent 28mm prime lenses. Compared to the DA at 28mm, the primes are infinitely better at f3.5 or wider, because the kit only goes to f4. At f4, the primes are noticeably better if you are looking for it. At f8, you have to look very hard. In the center of the shot, they are even.

At 50mm, the M50/1.4 should be a lot better than the DA. It is four stops faster, a really huge difference. That helps when you stop both lenses down to f8 - the kit lens is just one stop from wide open, the M is five stops down.

The next question might be, is it worth it for me to spend more and get a good lens? That gets tricky. It helps a lot to define your needs before looking beyond the kit lens. Good lenses are designed for a purpose, so a good lens is worth more to you if that's your purpose, and worth-less if you don't need it.
I'll try my own tests. I've shot in similar situations with my kit lens and prime, but never in exact conditions with similar settings. Should be interesting.

QuoteOriginally posted by twitch Quote
About the only time it would be hard to spot the difference would be outside on a sunny day shooting at f8+. I think about 5% of my pictures are like that. Otherwise a "good" lens will give superior results. Some times there is no other way to even get a sharp photo without a good lens (think indoor sports).

I completely disagree about only being able to spot the difference at large print sizes or pixel peeping. Good lens produce pictures that are different (in a good way) even in very small sizes. A FA31 indoor image shot wide open for instance can be spotted as better than the kit lens even at tiny display sizes.
Funny, because a lot of my shots take place in that range (sunny day, f8), which explains a lot.
03-03-2011, 04:44 PM   #14
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QuoteOriginally posted by JeffJS Quote
You Have a good lens. I suspect you just aren't making use of it though (unless you define good differently than I do)... The M50 f1:1.4 is probably one of the best in that range you'll find. The best part of it is, since you already have it, you don't have the pay the current ridiculous asking price for it..

Pentax 50mm f1:1.4 - a set on Flickr

I don't have any side by side tests with it though but I will say that (IMO), it makes the kit lens (18-55) look terrible, at 50mm.

Very true. I love zooms, and have been very satisfied with IQ from both the kit lenses that I haven't really felt the need for possible better IQ - so I hardly carry my prime. And when I do, it's mostly for its faster performance. I'll start evaluating IQ between the two more closely from now though.
03-03-2011, 05:15 PM - 1 Like   #15
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I'll endorse what other people have said about the 50mm 1.4. Mine's the FA model, so it's not exactly the same as your M model, but close enough. I also have the DA* 16-50 and the DA* 50-135 and they are both very fine lenses. I don't feel that I am compromising on IQ when I use my FA50 1.4 on my K5 instead of a DA* lens.

Richard.
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