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09-28-2009, 02:15 AM   #46
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QuoteOriginally posted by insulinguy Quote
...... does anyone know if you can do multiple images in the same frame? like sequencing? .....
Sure, that's what the Multi-exposure function is actually doing !

We do things like mounting the camera on a tripod, turn on E/V correction etc. to do multiple exposures of the identical scene, but that's really a specialised subset of the feature capability.

If I read the Pentax K-7 brochure correctly, they actually had in mind artistic blending of multiple images (like film days) when they offered this feature.
Of course, the users have found a lot of other applications like superb night-scene photography, even astrography...

09-28-2009, 03:18 AM   #47
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QuoteOriginally posted by Class A Quote
1. Is it 4^3 rather than 2^3 because the noise only grows with the square of the number of images and you are interested in increasing the bits above the noise?

2. Quite similar to "dithering" (intentional adding of noise in order to reduce quantization errors) in digital audio.
1. Exactly, SQRT(4)=2=one more Bit SNR (same as a resize to 50% step)
2. Exactly. I didn't know about it in audio (thanks for the remark). But it certainly is a well known technique with less than 24Bit image displays and printers -- like Floyd-Steinberg dithering.
QuoteOriginally posted by insulinguy Quote
like sequencing?
QuoteOriginally posted by kittykat46 Quote
they actually had in mind artistic blending of multiple images (like film days) when they offered this feature.
I apologize for my tech talk.
Indeed, an increase of artistic freedom was the real intention of the feature.

On a K-7, combine multi exposure with live view and you will be amazed!

It will overlay the previous images with live view and allow you to compose the artistic effect like no other camera on the market (AFAIK) allows.
09-28-2009, 12:24 PM   #48
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this is what i meant by sequencing - i thought THIS was possible with the multi exposure setting - but i think i am beyond wrong on this....i posted a thread in the PP forum but just wanted to throw this out there....i dont think it can be done in camera can it? multi exposure (to me) would allude to being able to do this - but i dont think the K20 does it....anyone?
09-28-2009, 02:07 PM   #49
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QuoteOriginally posted by insulinguy Quote
this is what i meant by sequencing - i thought THIS was possible with the multi exposure setting - but i think i am beyond wrong on this....i posted a thread in the PP forum but just wanted to throw this out there....i dont think it can be done in camera can it? multi exposure (to me) would allude to being able to do this - but i dont think the K20 does it....anyone?
Yes but no. That is if you did it in the camera you get like old film. You get more then one person but you see the background through them. So to get what you have here you need to do it in PP so you can cut the photo up into pieces. What you get for a photo in camera is the person looks like a ghost.

DAZ

09-28-2009, 02:11 PM   #50
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thanks daz - thats why i thought - you would get ghosted images - i want solid fugures -
it would be sick if you could do it in camera with the K20 - im not 100% sold on the K7 just yet and seeing as i just got the K20 last month - ill just have to work with it in PP. someone told me its layer stacking?? ill shoot something this week to try and hopefully it will be a success.
09-28-2009, 04:01 PM   #51
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QuoteOriginally posted by insulinguy Quote
someone told me its layer stacking??
It is easy, just select rectangular regions containing the person from images 2 to 5 and copy them into image 1 (each copy adds a layer). Then, combine all layers in image 1 into one. A 2 minute job. Of course, you need all 5 images to start with.

It will be more tedious to do this with persons overlapping each other
09-28-2009, 08:10 PM   #52
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I think this would be easy to do with multi exposure. as far as I am aware there is no time limit in between shots so the process would be;
-select number of shots
-position person for 1st frame, press shutter
-position person for 2cd fame, press shutter
and so on, when th final image is saved you will have the person visible in all poitions but in one shot. I will try this out ad le yo know if it works.

No it doesn't work, just tried it with an object on a table, 3 exposures, and the object appears in 3 locations but it is transparent. Does make sense when you think about it as the camera is combining 3 shots, only one in which the object appears.

Last edited by ozlizard; 09-28-2009 at 08:17 PM.
09-28-2009, 08:22 PM   #53
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QuoteOriginally posted by ozlizard Quote
I think this would be easy to do with multi exposure. as far as I am aware there is no time limit in between shots so the process would be;
-select number of shots
-position person for 1st frame, press shutter
-position person for 2cd fame, press shutter
and so on, when th final image is saved you will have the person visible in all poitions but in one shot. I will try this out ad le yo know if it works.

Say you take 5 shots and process in-camera. The probem is that you will have 5 exposures of the same background superimposed with the 5 different positions of the person. So the background will have a much higher opacity than the person, so the person will be ghosty (semi-transparent).

To do this properly in-camera I think you would need to use fill-flash to illuminate the person each time, with the background further away and thus less bright per shot (not right behind the person as in the example shown), so the background level does not overpower the foreground.

Or you can do in in masking in PP.

09-28-2009, 11:27 PM   #54
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Hello again ozlizard
Good to see that you are putting the K20 to good use. Some of the posts in this topic made me wonder whether some of the responders are confusing Exposure Bracket Mode with Multi-exposure Mode.
Am I correct in believing that you used Multi-exposure? Dosdan and others ask about exposure compensation. If those wondering read the manual they will find that when you set the number of shots to take the camera will compensate and give the correst exposure.
If the camera is set to exposure bracket with the compensation set to zero you get a set of images that Photoshop (and no doubt other software) can stack and blend.
This is great for fireworks. I just set the camera for auto exposure. lock my remote release on and keep shooting sets of 4sec, F8, 100 ISO until the buffer is full (if it does fill). Photoshop can blend the shots so that you can increase the "population" of bursts.
09-29-2009, 01:08 AM   #55
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Hi photog, yes there did seem to be a bit of confusion!. I have been experimenting with multi exposure with pleasing results. The image I posted in this thread was taken with 9 exposures and as I didn't have my ND filter at that time it allowed me to achieve that smoothed water effect and the softness to the clouds which I really liked as well. It does seem to obtain better dyamin range but I am not convinced of that as yet.
09-29-2009, 12:25 PM   #56
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I'm reading this thread trying to follow, but at the end of the day what is the real "purpose" for the multi-exposure. The mnual just says HOW to do it, but - as usual - not WHY/WHEN.
Since it's not doing exposure comp or giving you an HDR image, when/why would you want 3, 4 or even 9 images stacked on top of each other? I understand that's what "softened" the water & clouds in the above photo, but that can't be it's real "purpose"????

Tim
09-29-2009, 01:44 PM   #57
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thats kind of where im at with it tim - what is the purpose of the function really?
i want it to do what the photo i posted is like a sequence of multiple exposures on one frame- but its obvious to me now the K20 doesnt do THAT in camera. it seems like pentax's outlook to multi exposure is again to achieve maximum detail in all areas - but the name MULTI exposure - to me - implies something that we dont get. i like it - and think it is going to prove useful for correct and dynamic exposures - but creatively i wanted it to do something else
09-29-2009, 02:18 PM   #58
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QuoteOriginally posted by insulinguy Quote
thats kind of where im at with it tim - what is the purpose of the function really?
i want it to do what the photo i posted is like a sequence of multiple exposures on one frame- but its obvious to me now the K20 doesnt do THAT in camera. it seems like pentax's outlook to multi exposure is again to achieve maximum detail in all areas - but the name MULTI exposure - to me - implies something that we dont get. i like it - and think it is going to prove useful for correct and dynamic exposures - but creatively i wanted it to do something else
What the K20D (and the other Pentax cameras do) is what traditionally cameras did in the days of film for multi exposure. They make more then one exposure on top of each other. It is a creative and technical tool that was missing from most digital cameras but was available with film. That it is not the look you were looking for is not why Pentax added it to the camera. Like most things it is something that could be accomplished in a computer (and may be better) but until now not in the camera. Some people do not like to do anything on the computer but will if they can in camera. To each there own.

As to what it is good for it is kind of like what is a new born baby good for. As mentioned, blur water and sky when you donít have a ND filter (although this gives a look that is a little different), you can make ghost like images or if taken against a dark background it can look like the old portraits of a face next to some other object. I am sure there are other thinks as I canít think of everthing. Someone will come up with other things. From a technical side you can improve the DR or reduce the noise for some kinds of photos.

Like any tool some will never have a use for it but for others it may become a favorite tool.

DAZ
09-29-2009, 07:16 PM   #59
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QuoteOriginally posted by UpNorth Quote
I'm reading this thread trying to follow, but at the end of the day what is the real "purpose" for the multi-exposure. The mnual just says HOW to do it, but - as usual - not WHY/WHEN.
Since it's not doing exposure comp or giving you an HDR image, when/why would you want 3, 4 or even 9 images stacked on top of each other? I understand that's what "softened" the water & clouds in the above photo, but that can't be it's real "purpose"????

Tim
There is a brief write-up on the feature on the K-7 website

K-7 : Digital SLR Cameras : PENTAX

Its meant to work the same way multi-exposure was done in film. You take a shot of a scene, rewind the film, take a shot of a different scene. Getting the exposure right for both frames was very tricky on film, its a breeze on the K-7.
Some other things I've done with it
- low-noise night-time photography with excellent Dynamic Range 9 x 30 secs exposure done at ISO 100.

What some of the other posters want is what I call Non-Transparent image stacking.
You need to work accurately with a mouse and a decent-sized screen to do that, and it can only be done on a PC with post-processing software.
09-29-2009, 11:07 PM   #60
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Kittykat
The use is to allow you to undertake creative projects limited only by your imagination. Stacking V high ISO and appropriate blending mode will have a magical effect on grain.
Also Tourist elinination - street scene. (do Google search for info)
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