How to get K-r to focus in the dark?

awaldram said:

What Stern is complaining about has nothing zero zilch todo with your issue

Stern's and some others have noted that the kr when achieving lock under tungsten light may appear front focused.

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Well, that is not completely correct. Under tungsten light my K-r always front focused. BUT: Under any other low light (from what ever source!) the K-r wouldn't achieve correct autofocus too (usually front focus - tried it under various light sources)! My K-r didn't work where my K-m and K10D would work flawlessly. I had the K-r with Pentax service Germany twice (!) which led to some minor improvement concerning the front focus issue, but low light performance remained mediocre to very bad. Pentax Gemany sent me an e-mail upon my complaint, telling me they were working on a software fix both for the K5 and the K-r. Shortly afterwards, the K5 firmware-fix was issued... whilst for the K-r we are still waiting. I sent a number of test shots to my Pentax dealer on his request who checked them for focus accuracy and then with out hesitation he exchanged my K-r for a K7 body. The K7 isn't as good as the K-x/K-r in low light, but at least it works extremely accurately. If I had the choice between the K-x or the K-r, I'd go straight for the K-x (older and slower AF, but accurate). With the K-x, I'd only use the center point for focusing (what we did for ages anyway). Besides, the K-x is a bargain nowadays! All my Pentaxes (*ist DS, K-m, K10D and now K7) had a perfect AF performance, the new SAFOX IX AF-system seems to have some issues.

awaldram said:

There was a rumour that like the k5 Pentax would issue a firmware fix but htats all it ever been a rumour.

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This is not a rumor, this a fact - I have posted the e-mail I received from Pentax in this forum. Besides, I was not the only one who received written confirmation from Pentax that a firmware fix for the K-r was on the way (I received this e-mail in January and hoped for the fix to materialize a few weeks later...).

awaldram said:

Whether the kr is worse than any-other camera in this regard appear unproven with antagonist on both sides more interested in wining than the truth.

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Well, I have compared the K-r side-by-side with the K10D/K-m and K7. The K-r's SAFOX IX AF is faster than SAFOX VIII, but - at least in MY K-r - not accurate. I perfer accuracy over speed.

awaldram said:

As fro your problem (no lock at all) this is simply your below the light level the AF is designed to operate

Your AF will work from -1 to 18 EV but your biggest issue will be exposure is 1 to 21 ev so the AF should provide a lock in light levels the camera cannot expose for.

As to whether you will hit Sterns Kr bug I have no idea but you haven't hit it yet.

Many millions of people are happily using Kr's maybe they arn't very particular in their results, Or perhaps don't use them under low light, or more likley IMO their expectations are met.

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Nevertheless, good luck with whatever choice you make!
Stern

• very happy with his K7

;-)

awaldram said:

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If you just want a spot beam look for a used Pentax AF240FT flash (not made anymore). It has a very good spotbeam and can be set to only output the spotbeam (S.B. mode). You should be able to pick it up cheap. I've been using one for years when I don't need to use an actual flash.
Kent Gittings

The best AF assist lights are either with a flash red AF pattern or a built in camera one.

I was using my film Dynax 7 in complete darkness the other week and it could AF no problems with the built in red pattern overlay and further away than you might expect.

A single solid beam of light is a poor substitute for an AF assist I've no idea why some makers use this over the far superior red pattern overlay. The pattern can help the AF confirm even on pure white subjects it creates the contrast areas. Very useful..

Really pleased the torch worked for you

as for white and black

AF systems are passive the rely in the light received from the target. Black is the absence of light whereas white is the presence of all light.

Therefore the reflectivity of white is an order of magnitude greater than Black.

Also bear n mind light Vs distance is logarithmic for every doubling in distance you need 4 times the light power to achieve the same illumination.

So if you black coat has 1/4 of the reflectivity of the white Tshirt then the white t-shirt will work at twice the distance of the black irrespective of AF assist colour.

As for semi naked models I often think about shooting but rarely do But when I shoot people I try and get the eyes in sharpest focus and never is the face covered.

I would never be focusing on their clothed shoulders or tummy.

jungleexplorer said:

Well, I tried the flashlight trick and it worked. It took a bright light though to focus on the gazebo. I did some test shots of my son in the dark with a black jacket on. The camera could focus lock on him at 5 feet away with only the AF assist but not 10 feet away. I had him hold a white T-shirt in front of him at 10 feet and the camera could focus lock with only the AF assist light. I think the problem is the color of the AF assist not the brightness.

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Another thing you might want to consider:

I saw a comment in one of your posts above that said that "every 99 dollar point and shoot" you had could focus in the dark. You also have to remember that P+S cameras have teensy tiny little sensors, and teensy tiney little lenses, meaning you have near infinite depth of field. As a result, There is often very little actual autofocus that is going on with these cams!

DSLR's give much shallower DOF, which results in a more professional look, but makes effective autofocus much more of an engineering chore, especially given the other technical challenges listed by Antoine. While certain models do perform better than others, effective focusing in very dark conditions will be a problem for almost any SLR.

Okay. So now we know that I can take pictures of close subjects at night with the help of a bright flashlight (Torch if you are from England). But what if I were trying to take a panorama shot of a starry night sky? How would I take a picture when there is no subject to focus on? The reason I ask this question is because several year ago, I was up above the Arctic Circle and the Aurora Borealis was very active one night. Thank God I had my Sony DSC-V1 with me that has manual settings capability. There were a bunch of other people that only had standard P&S cameras and none of them could capture a shot of the Aurora Borealis. But I got some shots that even the locals said were some of the best they had ever seen. Several native artist asked for copies of the pictures so they could reproduce them on canvas for sale. My one sadness about it was the artifacts and noise that were in the pictures because of the high ISO setting I had to use in order to capture the pictures. I guess it was then that I was made aware of the beauty of night time photography and also of the ISO noise issue. Ever since then I have always wanted a camera that would perform better at night. Being a person of skimpy financial means compared to other Americans I cannot afford to spend thousands on a pro level camera. When I discovered the K-x and K-r, I was thrilled at it's low light performance in such an economic package. Finally I could afford to buy a camera that would do a much better job if I ever have the pleasure of going to the Arctic again. But now I am worried that I don't know how to capture such a photo should the opportunity ever arise. So I am asking for your help to educate me on how to do this with the K-r. Here are some of my Aurora Borealis pics I took with my DSC-V1

How well would a laser pointer work? Has anyone tried it?

I'm fairly sure that none of the recent Sony cameras have had this highly effective laser hologram assist light. I did read that Sony were worried about being sued so stopped fitting them, but I've no idea if that's just a rumour.

labnut said:

How well would a laser pointer work? Has anyone tried it?

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Yes, I have used a red pattern 1 milliwatt cheap laser and it works brilliantly with my K100D. A single point laser is nowhere as effective.

Simple answer: Setting the focus manually to the Hyper focal distance for your focal length and F-Stop. Garanteed to work every time.

It's good practice to know the HFD of your wide angle lenses, at one or two apertures.

DOFMaster can give those to you. I think you can also print them on a small piece of paper for reference.

Worst case, focus on infinity....

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Steph
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Wouldn't you just manually focus at infinity? Especially with a wide angle focal length, pretty much just set it to infinity. No need for AF, which will only mess you up.
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Russ Houston said:

Wouldn't you just manually focus at infinity? Especially with a wide angle focal length, pretty much just set it to infinity. No need for AF, which will only mess you up.
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Please understand that I have never used a manual focus lens before so I don't know what focusing to infinity is. Is this simple to do?

Thanks for the info. I have all ready ordered a couple of kaleidescope laser pens to try, one red and one green. If they work as good as the hologram assist light on my Sony V1 it will be a cheap, lightweight fun solution to this problem.

I have come to this understanding as a result of of this thread. It is something I was not aware of before. Thanks for the advice.

dcshooter said:

Another thing you might want to consider:

I saw a comment in one of your posts above that said that "every 99 dollar point and shoot" you had could focus in the dark. You also have to remember that P+S cameras have teensy tiny little sensors, and teensy tiney little lenses, meaning you have near infinite depth of field. As a result, There is often very little actual autofocus that is going on with these cams!

DSLR's give much shallower DOF, which results in a more professional look, but makes effective autofocus much more of an engineering chore, especially given the other technical challenges listed by Antoine. While certain models do perform better than others, effective focusing in very dark conditions will be a problem for almost any SLR.

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granted, the really tiny sensors such as on an iPhone 4, DO have large depth of field

still, my iPhone DOES focus

more importantly, my superzoom DOES focus, as is evidenced by shots such as those below:

bee collecting pollen on apple tree (note the bee and flower are in focus, the background not)
http://www.flickr.com/photos/antoinebach/5672001350/in/photostream

pheasant (note the bird is in focus while fore- and background, are not)
http://www.flickr.com/photos/antoinebach/5535019527/in/photostream

horse chestnut flower bud at long tele (blurred background)
http://www.flickr.com/photos/antoinebach/5558673880/in/photostream

Sorry, yes it's very easy. In this case since you're focusing on the sky, basically you can just set the camera to MF (switch on the front of the camera) and then rotate the focus ring on the camera to the infinity symbol. That just means it's focused out as far as it can go.

On some lenses, the lens will also have a switch for manual focus and you'll want to switch that as well, or you could damage some gears in the lens.

Since it's dark, you don't even really need to look since infinity is pretty much all the way at one end of the focus.

Note that occasionally you can get a lens that will focus "beyond infinity" meaning that it will be slightly out of focus if you just turn it all the way. Check your lens during the daytime by manually focusing to infinity (as described above) on a distant building (as in many miles away, like the downtown skyline). For something like that, the camera should be able to auto focus on that, so you could first let the camera AF, then try it with manual focus to see if you get the same results. If you do, then you're better off for it, know how your lens will focus when you manually try it.

All of this may sound complicated but it's really very easy. Just keep trying it out like you're doing. You'll figure it out and next year you'll be wondering why you were having such a hard time.

Good luck!
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Thanks for the instructions. I will try this out tomorrow. I just found the manual switch on the camera today by accident. I accidentally pushed it half way between AF and manual and the camera started messing up big time. It scared me to death. The focus motor would just keep running when I pushed the shutter button. I immediately called Pentax customer support and they walked me through some checks and told me to check the AF/manual button. I have to say that I believe that Pentax has the best customer support I have ever seen. I have called them twice in two days. I got through fast and the support reps were intelligent and could actually speak English. This is a far cry from what I am used to in the computer world where you spend hours on hold only to speak to an East Indian robot that is following instructions on a screen and will short circuit if you ask them to step outside the pattern of their protocol to actually help you.

Russ Houston said:

Note that occasionally you can get a lens that will focus "beyond infinity" meaning that it will be slightly out of focus if you just turn it all the way.

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Russ

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The 18-55 kit lens on my Kr will do this at 55mm.
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Peter.

like I said, these will chronically have a much easier time focusing in lower light levels. Because they focus off a much larger sensor, and all the light gets to it not just part of the light.

This means things like:

• Panasonic GH2 (looks like a small DSLR)
• Panasonic G2 (looks like a small DSLR)
• Panasonic GF-1 (looks like a compact but is bigger once you add a lens), or its cheaper sibling the GF-2
• Olympus EPL-1
• etc

It's this, or giving up on a DSLR, or needing really powerful assist lights if you're going to do a lot of shooting at night.

It's an inherent weakness of the DSLR design - and note that the DSLR design is completely obsolete for the digital era anyway.

antoineb said:

It's an inherent weakness of the DSLR design - and note that the DSLR design is completely obsolete for the digital era anyway.

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You were going great guns until that statement

Pretty brave in the middle of a dlsr forum though obviously not true the dlsr is far from obsolete being one of the most common types of camera in the world and the design is dynamic changing from model to model.

I may have agreed if you'd said then life of the dslr is limited with the onset of current technologies (oled, led CD etc).

But most of the dlsr design will remain intact even if the mirror is removed in favour of Evf's.

Even if obsolete like fountain pens there's just something nice about using them

But for now the dlsr is far from obsolescence with the probable replacement technologies still to immature to compete at this time.

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