Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax Lenses

Thread Tools Search this Thread
Old Dec 16, 2010, 9:50 PM   #1
Senior Member
Join Date: May 2010
Posts: 105
Default Low light versatile lens help for my kx

Hello fellow Pentaxers -

Looking for some recommendations and guidance on adding or swapping out the kit lens on my bag. I am currently packing the KX with the double-kit lens combo. I am extremely pleased with both kit lenses for outdoor use, and I am getting better with the 18-55 indoors, but I usually have have to bump up the ISO which adds noise. My indoor subjects are my 2 sons and at 6 months and 2 years, they are not good at staying still.

With that being said, I am looking to possibly upgrade my shorter kit lens with something faster, or simply adding a better, indoor low light capable lens that will assist in not missing out on the action.

The budget right now is limited with 2 little ones, so I want to keep it as cheap as possible, but I am willing to stretch for some value, but would rather save the money while getting decent value.

So, first general question;

What speed or lens aperture will adequately perform indoors for lamplight child chasing action? Is f2.8 enough?

I was looking at the Tamron f2.8 17-50mm as a replacement for the Kit, but I was not sure if that would be fast enough. In reviewing some info online I guess that lens is f2.8 at max zoom too, which should help.

As a 6 month dSLR user I am really green and any pointers or suggestions are welcome.
mackloon is offline   Reply With Quote
Sponsored Links
Old Dec 16, 2010, 10:01 PM   #2
Senior Member
mtngal's Avatar
Join Date: Nov 2005
Location: Frazier Park, CA
Posts: 16,004

The tamron is reputed to be an excellent lens (I don't actually have any personal experience with the faster lenses in this range, though I'd like to get one) and I've seen some really wonderful shots taken with it. Be aware that if you get an f2.8 zoom lens, it's going to be a lot bigger and heavier than your kit lens. To go faster than f2.8 you'd need to get one of the prime lenses - the new DA 35mm f2.4 might be very good for your purposes and it's priced very reasonably. You lose the zoom capability and 35mm is about what the old 50 lenses were on film cameras. You could also get the FA 50 f1.4, an excellent lens but it's more expensive and I find it too long for quick shots indoors.

You might want to think about buying an external flash that you can bounce off the ceiling as an alternative. That way you'll get more light on your kids and still have even lighting (not the harsh directional lighting from the on-board flash).
mtngal is offline   Reply With Quote
Old Dec 16, 2010, 10:12 PM   #3
Senior Member
Join Date: May 2010
Posts: 105

Thanks for the info... I was able to get a Vivitar 383pen for like $25 used on an eBay misjudging. It seems to fire right, but I can't seem to decide if it is broken, I need more practice or I am not setting it right. Also, it is big...

I was hoping that I could get a faster lens, off the kit lens, sell the flash for a profit and end up with better pix. Is there a bounce attachment or diffuser that I could use that would eliminate my need for this big flash? It is too big I don't really want to use it.
mackloon is offline   Reply With Quote
Old Dec 16, 2010, 10:15 PM   #4
Senior Member
Biro's Avatar
Join Date: Mar 2008
Posts: 834

Since you're talking about indoor photography, the lack of zooming ability with the DA 35mm f/2.4 shouldn't be a problem. With a price of $219 (and maybe less), this lens is packed full of value. I personally own this lens and can heartily recommend it.


Biro is offline   Reply With Quote
Old Dec 16, 2010, 10:19 PM   #5
Senior Member
bigdawg's Avatar
Join Date: Feb 2005
Location: Thach Alabama
Posts: 14,981

I use a Pentax F 50mm f/1.7. Very sharp and very fast. About 200 bucks on the Bay.
Big Dawg
bigdawg is offline   Reply With Quote
Old Dec 16, 2010, 10:37 PM   #6
Senior Member
Join Date: May 2010
Posts: 105

I considered the DA 35mm as a solid additional option, and I was looking at the faster lenses like the 1.7 50mm big dawg mentioned.

I don't mind a prime lens, I just feel like I will struggle when I want a wider shot.

Maybe not, but that is my hesitation.

From a % standpoint, how much faster is the Tamron f2.8 than the f3.5 kit, and then compare both of those to the 2.4 Biro mentioned and the 1.7 mentioned by bd.

Not sure how to do the math, this way I can understand better what I am gaining by sacrificing variable zoom or width.

Thanks for the help thusfar.
mackloon is offline   Reply With Quote
Old Dec 17, 2010, 7:47 AM   #7
Senior Member
snostorm's Avatar
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,769

Hi mackloon,

This is a trickier subject than most consider it. Kids indoors are more demanding than sports or birds in flight outdoors. If you look at the focusing scale of any lens, the rotaional distance between minimum focusing distance (MFD) and say 15 ft is usually twice or 3 times the rotation of the difference between infinity and 15 ft. Also, DOF decreases with a given FL and aperture as the distance to the subject shrinks. Both of these factors hurt you when shooting moving subjects in close quarters.

A lot of people complain that it's easier to shoot candids of kids with a P&S than with a DSLR, and they are probably correct in most circumstances. There are three factors at work here.

1. A P&S will have slower focusing, but much greater Depth of Field, so it has to adjust focus considerably less and to a lesser degree. The much smaller lenses also help here as there's less mass to move and they are usually slower aperture max lenses which add to the DOF.

2. There are lower expectations for P&S image quality, as the usual output is 6x4 prints or web transmission at low res.

3. The auto exposure systems of most of these cameras will trigger flash automatically without any intervention from the photographer.

Although I love to suggest how others spend their money, I'd suggest that you try some other things first. . .

The first thing that you should do is evaluate the pics you've taken and determine why they aren't cutting it for you. Are the kids out of focus, the AF too slow, is there too much motion blur from their movement.

Consider adding more light, either with more lamps or higher wattage if your lighting sources allow it. 3 way bulbs might be an answer, and the new compact fluorescents use less current, but output more light with less heat, so higher wattage equivalents can be substituted even in older fixtures. The extra light might not be desirable most of the time, so you need to choose a solution where you can change this according to conditions. Adding light would help with AF speed, and shutter speed, and it would cut the need for higher ISO.

You'll never get to the point where indoor light is equivalent to sunlight, but you can increase your odds of getting the shots you want.

If focus accuracy is the problem, consider that your camera focuses with the lens at max aperture. Very wide max apertures bring shallower DOF, so a faster max aperture lens has to refocus more often and focus becomes increasingly more critical as subject distance gets closer. Sometimes slower is better.

Let's say that you're shooting at 50mm and 10 feet.

Your DA 18-55 f3.5-5.6 at 50mm will be assumed to be at f5.6. At 10 feet, the DOF is 2.76 ft.

With your DA 50-200 f4-5.6, at 50mm it's f4 max, so the DOF is going to be 1.94 ft.

Let's say you pick up an F or FA 50 f1.7. DOF at 10' is going to be .81 ft

Remember that we're talking about AF, not exposure DOF, and the lens always focuses at max aperture. Which lens will allow easier AF for the camera body? A lens that has to refocus at 3 ft of movement or one that has to refocus every 10 inches? Faster is not always better. . .

If you're having trouble getting a focus lock, so you're getting frustrated that your camera won't let you take a picture when you want one, there are two things that you can do.

1. Try to prefocus at the distance you expect to shoot. AF then only needs to touch up the focus, and even with a slow AF camera and lens, this is usually pretty fast. The Kx is a K-7 generation SAFOX VIII, and when the initial focus is pretty close, it should be fast enough. If you have the "L" versions of the kit lenses, they don't have Quick Shift, so the easiest way to prefocus is to aim at something stationary at a similar distance and let the AF system get a lock, then shift to your subject and see if it can get a quick lock.

2. Try shooting in AF-C. This mode is shutter priority, so the camera will fire, even if there's no focus confirmation. If you hedge with a smaller aperture to get greater DOF, then shoot when you see that focus is close but not necessarily wait until focus is confirmed, you may get lucky more often than not. This is where more light and higher ISO work to your advantage by allowing you to shoot at smaller apertures.

Don't obsess about noise. This is a major problem with digital photography. People view their pics at unrealistic magnifications on screen because it's so easy, and they can, but take a look at your parent's favorite memory shots and imagine how they'd look at 11x14 or bigger -- sometimes IQ is trumped by capturing the moment. You'd probably be surprised at how what looks like a disturbingly noisy shot on your computer screen prints at 4x6 or even 5x7. Add one of the newest Noise Reduction programs ( I like Topaz Denoise), and with the Sony Exmoor sensors (like your Kx has), you can get pretty clean images at surprisingly high ISO. For really noisy shots, try downsizing to between 2000 to 2500 pixels on the long side before NR, and you'll be surprised how clean the shots can get -- and you still have plenty of resolution to get a good 8x10 print if you want. (200-250 DPI)

LBA is fun, don't get me wrong. I'm more guilty of this than most. But one of the first things that I'm discovering with the outrageous high ISO capabilities of my new K-5 is that my "lowly" kit lenses and my "too slow for indoor" DA 18-250 f3.5-6.3 are gaining a second wind shooting my cats indoors at ISO 3200 - 12800. The high ISO makes available light shooting ridiculously easy. Are these shots "art" -- nah -- but they are fun, and they capture moments that I'll enjoy for years to come.

So bottom line -- get some brighter bulbs, shoot higher ISO, use smaller apertures, use AF-C and shoot for the moment, not for perfect focus. It'll only cost you a few bucks -- and if you don't like the results, you can always let LBA take over -- which is probably inevitable anyway. . .

snostorm is offline   Reply With Quote
Old Dec 17, 2010, 1:52 PM   #8
Senior Member
Join Date: May 2010
Posts: 105

Thanks for the info....

.... Now let me digest.

So, if I was going to get a lens for indoor use would you get the tamron 17-50mm 2.8f and sell off the 18-55mm dal kit lens, or just add the 35mm prime 2.4f to your collection.
mackloon is offline   Reply With Quote
Old Dec 17, 2010, 2:35 PM   #9
Join Date: Aug 2004
Posts: 8,528

Be aware - f2.8 isn't that fast. With a moving 4 year old you're still looking at ISO 1600-3200 (with a heavy dose of 3200 at night). I've shot a lot of low light sports and f2.8 and faster lenses are great for that - but houses don't have the light that gyms do. When I take shots of kids indoors, without doubt a good external bounced flash produces much better results than trying to use my 2.8 or 1.8 lenses. So be prepared - especially if you lay down a few hundred on an f2.8 zoom - you may find you're still not getting fast enough shutter speeds and yet still have to deal with ISO 3200. Of course, not all flashes are created equal - I'd suggest a good P-TTL capable flash instead of the cheapest automatic you can find.
JohnG is offline   Reply With Quote
Old Dec 17, 2010, 2:48 PM   #10
Senior Member
Join Date: May 2010
Posts: 105

Can you recommend a smaller, bounce capable, less expensive p ttl flash?
mackloon is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 10:14 PM.