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02-16-2010, 03:20 AM   #1
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Pentax Low Light Focus

Hello to all!

I just recently joined the Pentaxforums community, and I would like to ask some questions about the K20D and K7
I will start making (also) wedding photography and want to buy a K20D or K7 with the 17-70 f/4 lens + Metz 48 AF1.
I've read that the Pentax DSLRs have a "low light focusing problem".
What is exactly low-light?

I also thought to buy D90 or 50D, but I like very much the rich feature set of the Pentax cameras.
What do you think?
What about wedding photography with Pentax cameras?

Thanks in advance,

02-16-2010, 03:27 AM   #2
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With an AF assist lamp on the flash unit, the K20D can focus in pitch darkness. You can set the flash unit to "SB" mode and use it only as an external AF assist lamp...and use fast lenses to avoid the flash itself.

Whatever equipment you use, I hope your first wedding "experiment" is for free and you aren't the primary shooter, btw.
02-16-2010, 03:32 AM   #3
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Wow!

That was a fast reply
Thanks for your answer.
What do you think about the K7?
I mean the K7 would be better for wedding photography?

Thanks,
02-16-2010, 05:09 AM   #4
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AF in low light with Pentax has been rather an exercise in frustration for me.
The last wedding I shot (using K7), I was finding the AF failing more than working at light levels that I thought should be high enough to have the AF working.
The light was such that I was shooting my available light stuff at ISO 400, f/2.8 @ 1/15 or 1/8 second.
The light levels were bright enough that the AF lamp wasn't coming on, dim enough that the AF wasn't locking on reliably.
The lens in use was the 31/1.8, so I wasn't using a slow F/4 zoom either.
Add to this that the Pentax AF just isn't very fast as compared to the competition and this is an area where Pentax still has some work to do.
I would seriously reconsider the f/4 lens if you are going to be shooting weddings with a Pentax, or else reconsider the brand if you are married to the idea of an f/4 zoom lens.
The K7 AF is better than the K20 AF, but not significantly.

02-16-2010, 08:21 AM   #5
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I thought about lenses with f/2.8, but I think that the f/2.8(or faster) lenses have too shallow DOF, and that's why the Pentax cameras can't always focus with them.
Am I right?

K20D and K7 owners.... What do you think of this?

Some info please, because I'm getting a little desperate...
I want to buy a Pentax, but I will shoot in low light.....

Thanks in advance,
02-16-2010, 09:46 AM   #6
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I dont have any significant experience with other brands so I cannot make the comparison...

however...

I have a K20D with 16-50 and find that if I can visually see contrast (i.e. all cases but pitch black) through the VF the camera will also find it and focus correctly.
When I stick the FGZ-AF540 on top I can even focus in pitch black....
Its also down to technique, knowing the equipment and how contract detect AF works... if you dont align the focus points to a point of contrast you will never get the camera to focus.

I would seriously consider the "timeline" of your move into wedding photography... I think its a very tough business, your customers have extremely high expectations... not a place to be unless you really know what you are doing. Dont consider that you can pick up a camera and the next day be a wedding photographer.

Also, the DOF is a function of both the aperture and distance from subject... it also may or may not be a problem depending on what you are trying to accomplish from a shot... as far as I am aware it is not a function of pentax vs. other brands.
02-16-2010, 10:18 AM   #7
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My reply won't be pleasant, but you have a Canon entry level kit with flash, and now looking for a Pentax kit. The question you have asked suggested you have known little on photography, let alone wedding photography. Now I have nothing against you but just feel that you are far from ready for wedding photography, though to some, it's fast money.

But to answer your question, there is no practical reason to go Pentax for wedding photography.
02-16-2010, 10:36 AM   #8
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Thanks for your reply
I have a "starter" Canon kit, because I didn't had money to buy a better kit
I already was a wedding photographer on some weddings, not on many though
Now, I already sold my kit and want to buy a new one, and as I will make also wedding photography I have to choose one with "fast" autofocus to catch the moment.
Originally I wanted to buy the D90 kit + flash, but after that I saw the Pentax DSLRs with a wealth of functions.
Then I wanted Pentax, but after that I read a thread on a forum, that the Pentax cameras has a difficulty autofocusing in low light.
Now I really don't know which to choose. )
Also, I can borrow some money from my brother and I could buy also the 50D + 17-85 + flash.


Last edited by indy1984; 02-16-2010 at 10:37 AM. Reason: -
02-16-2010, 11:26 AM   #9
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Nikon will beat everyone else on TTL & wireless flash. Also, you only need some base set of features to get the job done. Unfortunately, Pentax is not high on AF tracking or low light AF (which also much depends on lens speed too). But then again, there are different styles of shooting and not everyone needs AF tracking.
02-16-2010, 11:27 AM   #10
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QuoteOriginally posted by asdf Quote
With an AF assist lamp on the flash unit, the K20D can focus in pitch darkness.
which is very annoying

and not all that predictable

also non functioning if you have an external flashgun
02-16-2010, 11:37 AM   #11
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QuoteOriginally posted by indy1984 Quote
I thought about lenses with f/2.8, but I think that the f/2.8(or faster) lenses have too shallow DOF, and that's why the Pentax cameras can't always focus with them.
Am I right?
This is not true. In fact the opposite is true. An f/2.8 lens will make it easier to focus because the sensor has twice as much light to use as an f/4 lens.

It is a well established fact that the SAFOX AF system in Pentax is one of the brand weaknesses. (the primary weakness as far as I am concerned) In every independent test I have ever seen, SAFOX starts having trouble below EV5. My experience with all of my Pentax DSLR's are the same. That doesn't mean that it won't focus, but you have to find ways to work around these limitations as many of us have. There are some very successful wedding photographers on this site, so it is obviously not impossible.
02-16-2010, 11:47 AM   #12
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QuoteOriginally posted by Gooshin Quote
which is very annoying

and not all that predictable

also non functioning if you have an external flashgun
???

I'm talking about the AF assist lamp on the external flashgun. The red thing.
02-17-2010, 12:52 AM   #13
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Thanks for all your answers!
PentaxPoke mentioned that there are wedding photographers on this site, who are using Pentax gear. What they think about this low light issue?
02-17-2010, 05:11 AM   #14
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I have shot second at a couple of weddings using K20, 16-50, 50-135 and had no real problems. With my K20 I can comfortably go to iso 3200 for situations with low light and more action. If I need faster shutter speeds than that an external flash is necessary.

As far as the auto focus goes, it is what it is. Once you learn how to make it work for you, you look for areas of contrast and focus on them. At the same time, it can be really slow. I think the K7 is faster and a little more consistent with focusing than the K20. Learning your equipment is key -- you don't want to be in the middle of a wedding trying to figure something out.
02-17-2010, 09:42 AM   #15
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QuoteOriginally posted by asdf Quote
???

I'm talking about the AF assist lamp on the external flashgun. The red thing.
you mean the infared beam?

I dont know what gun you have, but my AF540 is still very slow and close to unusable in extreme darkness, it still needs something contrasty and somewhat reflective to focus on.

it may very well focus in pitch darkness... eventually, after lots of frustration and screaming.. your subject may have fallen asleep by that point too...
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