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01-22-2018, 07:27 AM   #1
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The best way to use Bulb mode?

Hello,

I have used the 30 seconds exposure for night shots and got some really good results. However, I've never tried a longer shot (meaning using the Bulb mode), and now I would like to play with it. But I have some questions:

- It seems that, in Bulb mode, the only option is to press and hold Shutter button, and release it when you want to stop the exposure. This is not convenient for me, I don't like to have to keep hold of a button (even it's a wireless remote one) for 5 minutes, I prefer the traditional method, pre-setting the shutter time, press the shutter button 1 time, then voila. Do I miss something, or if that's the case, is there a way to work around?

- If the shutter time is decided by the photographer (e.g he holds the button until he thinks it's enough(, then how do proper exposure be calculated? I use Av, TAV and P mode a lot, they have 1 thing in common: the camera calculates exposure values for me (except for the ones I set myself), now with Bulb mode, would that mean I have to do it manually?

- Finally, if one likes to experiment with some daylight long exposure photos, for example to blur the sea, what type of ND filter is most suitable? ND4, ND6 or ND10?

I'm sorry if any of the question seems so obvious to you. Thank you very much in advance ;-)

01-22-2018, 07:56 AM   #2
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Check your camera manual. Don't know what you are using but there may be options to press and hold/press and press again/press green button and enter a time. These three options are available with the K-1.

Best to use a wired or wireless remote to trigger the shutter too.
01-22-2018, 08:22 AM   #3
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Which model of camera do you have? Check the manual as Peter suggests.

You have to set the exposure yourself. You can always do test exposures at wider apertures and higher iso to keep the shutter speed low, then adjust accordingly for the long exposure.

If you're hoping to massively blur moving water in daylight, get the highest ND filter you can find. 10-stops at least.
01-22-2018, 08:23 AM   #4
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Bulb exposures are a little bit guess-and-by-gosh which is considerably more practical with digital cameras than it was with film where you didn't see the result until the film was developed. In any case, unless you can meter on something and let the camera do its thing, there is a certain amount of trial and error involved in getting the best bulb exposure which often lies outside the normal metering range of your camera anyway. In bulb mode, it just the combination of aperture (including any ND filtering) and shutter time. Usually the aperture is set at an optimum value and several exposure times are tried for the best shot or you can combine several using HDR software, after the fact.

For daytime, long exposures you may need ND filters beyond 10 density. Those are available through photo outlets (e.g., B&H) up to some fairly high densities. The key thing is to obtain a high density filter which is neutral in its color rendition which most designed for ND use are.

If your camera doesn't have the capability for "toggle" bulb (one press starts and second press stops) exposures, you may be able to find an add on (plug in) device which will convert your camera to doing that (plus program long exposures automatically). There are several on the market but finding one compatible for your camera is important so check out what is available and compare it to your camera specifications.


Last edited by Bob 256; 01-22-2018 at 08:28 AM.
01-22-2018, 08:31 AM   #5
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QuoteOriginally posted by Bui Quote
It seems that, in Bulb mode, the only option is to press and hold Shutter button, and release it when you want to stop the exposure.
You have the option on your KP for either traditional "B" mode (hold for the full time) or "T" mode (press once to open and once more to close).

Menu >> C1 >> 7 Bulb(B) Mode Options

QuoteOriginally posted by Bui Quote
the camera calculates exposure values for me (except for the ones I set myself), now with Bulb mode, would that mean I have to do it manually?
Yes, you will have to calculate the exposure yourself. Bulb is always manual.

QuoteOriginally posted by Bui Quote
what type of ND filter is most suitable? ND4, ND6 or ND10?
How dense a filter depends on how long an exposure you intend. You can calculate which filter by metering the scene without the filter on.

As noted by @pschlute, bulb exposure is usually done with a remote release. With the KP, that means any of the phone app, tethered to a computer, or a wired release connected to the MIC/Remote port. A wired remote would generally be my first choice except that with the KP, the Pentax remote (cable switch CS-310) has been hard to come by. Reports on this site indicate it is possible to adapt commonly-available (and cheaper) third-party remotes for Pentax/Canon by using a four-pole 2.5mm plug adapter.

Have fun


Steve

Last edited by stevebrot; 01-22-2018 at 10:31 AM.
01-22-2018, 08:52 AM - 1 Like   #6
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Pschulte has the answer to your first question. The K-1 (with firmware of 1.4 or later) will let you set the bulb shutter times of up to 20 minutes.

Bulb is strictly manual exposure. You'll need to do some experimentation or math or both to get what you want. Moreover for night photography, the scene is often too dim to get an accurate meter reading and you probably don't want a scene that is 18% gray like a daylight scene. For night shots, there's no hard and fats rules for exposures because it varies so much with the phase of the moon, time of night, and light pollution. The beauty of digital is you can experiment as much as you want -- there no costly film to waste.

One trick is to take test shots at the highest ISO your camera can do until you are happy with the exposure. Then drop the ISO and multiply the shutter time. Thus if ISO 51,200 and 1/4 sec looks good, then try ISO 100 and (1/4 sec)*51200/100 = 128 sec = 2 minutes.

You can do the same exposure-estimation trick with aperture -- take test shots with the lens wide open (and short shutter times), then count the number of stops or half-stops to reach the desired aperture and change the shutter time by the same number of stops or half stops.

You can do the same exposure-estimation trick with an ND filter -- take test shots without the filter (and short metered or unmetered shutter times), then screw on the filter and change the shutter time by the number of stops of attenuation provided by your filter.

Good luck & have fun!
01-22-2018, 09:39 AM - 1 Like   #7
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QuoteOriginally posted by photoptimist Quote
One trick is to take test shots at the highest ISO your camera can do until you are happy with the exposure. Then drop the ISO and multiply the shutter time. Thus if ISO 51,200 and 1/4 sec looks good, then try ISO 100 and (1/4 sec)*51200/100 = 128 sec = 2 minutes. You can do the same exposure-estimation trick with aperture -- take test shots with the lens wide open (and short shutter times), then count the number of stops or half-stops to reach the desired aperture and change the shutter time by the same number of stops or half stops.

Some great tips and tricks there, thanks! I'll be remembering those pointers.


BTW, with film we always had to factor in the "Reciprocity Failure", from about 30 seconds plus .... this in practice usually meant doubling the exposures as a rough approach. Am I to right to assume that this does not apply to digital long exposures?
01-22-2018, 09:50 AM   #8
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If you have the K-1, K-70, KP or newer, you can also just dial in the bulb exposure time, up to 20 minutes. It's pretty convenient!

Otherwise, the 2-press approach (preferably) coupled with a remote or cable release will work great too.


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01-22-2018, 10:06 AM   #9
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QuoteOriginally posted by mcgregni Quote
Some great tips and tricks there, thanks! I'll be remembering those pointers.


BTW, with film we always had to factor in the "Reciprocity Failure", from about 30 seconds plus .... this in practice usually meant doubling the exposures as a rough approach. Am I to right to assume that this does not apply to digital long exposures?
Correct. Digital sensors don't show reciprocity failure.

That said, I find that the amplified noise at extreme ISO might make the high ISO short shutter image look a bit brighter than the corresponding low ISO long shutter image. As with so many aspects of photography, the rules only get you close to the right exposure. Experimentation and experience provide the tweaks.
01-22-2018, 10:15 AM - 1 Like   #10
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Answers can vary by camera.

It seems that, in Bulb mode, the only option is to press and hold Shutter button, and release it when you want to stop the exposure.

My K-5 and K-1 have a menu setting to change how bulb mode works. You can press the button once to begin exposure, then press a second time to end. This is better than having to hold the button but still creates too much risk of shaking the camera during exposure. Consider a remote (wired, wireless, or phone app).

I have a generic wired intervalometer (Shoot brand, but Neewer and others are the same) with a locking shutter button. I keep the default menu settings for bulb mode.

I prefer the traditional method, pre-setting the shutter time, press the shutter button 1 time, then voila.

The K-1 has a countdown timer in bulb mode that can do this. Why they did that in Bulb mode rather than Manual is a mystery to me, but it works. I've gone as long as 30 minutes.

If the shutter time is decided by the photographer (e.g he holds the button until he thinks it's enough(, then how do proper exposure be calculated? I use Av, TAV and P mode a lot, they have 1 thing in common: the camera calculates exposure values for me (except for the ones I set myself), now with Bulb mode, would that mean I have to do it manually?

Bulb mode behaves more like Manual mode; you always decide exposure length whether it's by holding a button or entering a time. Trial and error works. Or you can use an autoexposure mode to get an estimate, then flip to bulb mode and adjust from there.

Finally, if one likes to experiment with some daylight long exposure photos, for example to blur the sea, what type of ND filter is most suitable? ND4, ND6 or ND10?

ND filter naming can be confusing: ND 64 and ND 1.8 can be the same thing! Check filter specs for the number of "stops". 1 stop = double exposure time. For daylight long exposure, 10 stops is often good starting point because it gives 1024x exposure time, which would turn a 1/125 exposure into an 8 second exposure.

The K-1 and some other cameras have special shutter modes that blend multiple exposures. This can simulate an ND filter when you don't have one, or give the effect of a darker ND filter than the one you have.
01-22-2018, 10:29 AM - 1 Like   #11
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You should be able to select (in the camera's menu) whether you press and hold or whether one press of the shutter release opens the shutter and a second press closes it. Check your camera instruction book. From what you seem to want, I'd suggest a remote release. When I want precise multiple exposures, I use the Vello Shutterboss. It allows me to set the exposure time and number of exposures (and a lot more. It's a handy device.). Attach it to the camera, set the time/number of exposures, press the button and go get a cup of coffee. B&H or Adorama have several brands and models. Just make sure that it will work with your particular camera. Determining long exposure times is a matter of guesswork and experience. Look up the sort of images you want to produce to get an approximate beginning time and work from there. Reciprocity failure isn't a problem with digital cameras. Reciprocity failure is a function of the layers of emulsion of color film. No film. No problem. You should note that if you're doing long exposure night sky photography the colors will seem wrong. The eye perceives the night sky as a different color than it actually is. That can easily be corrected in post processing.

DeadJohn used the word I should have used. "Intervalometer". The Shutterboss is an intervalometer and that's what I should have written instead of "remote release".

Last edited by gifthorse; 01-22-2018 at 10:33 AM. Reason: Amplifying info.
01-22-2018, 11:49 AM   #12
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Bulb equals experimental. Plenty of test shots and changing settings. I use my remote when shooting in bulb or the 2 second delay.
01-22-2018, 01:57 PM - 2 Likes   #13
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A point to add. If you are using long exposure make sure you use the viewfinder blind that is supplied with your camera to prevent stray light entering.
01-22-2018, 08:23 PM   #14
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There are 3rd party wired remotes with long exposure timers (up to 99 hours 59 min 59 sec in 1 sec increments). Provided your body has a wired remote port. You may need an adapter for the KP although it wouldn't surprise me if some of these remotes now come with the adapter or appropriate plug.
01-30-2018, 02:46 AM   #15
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Thank you for great advices. I will do some experiments this weekend on my ND filter arrives :-)
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