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05-08-2008, 04:36 PM   #1
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Exposure time limitation while using manual lenses?

Hello,

I am new here and new to Pentax. I am not however new to photography. I have a question regarding exposure time while using manual lenses.

Shooting in the aperture priority mode with F11 and several stops of ND in front of the lens. I am shooting a long term timelapse of a construction project. I want an exposure time of about half a second in full sun in order to have good motion blur.

I would expect the camera to expose at half a second in full sun during the day, and up to a maximum of 30" at night.

When I attach an M42 mount lens via the official Pentax adaptor (either a zeiss or a pentax super takumer) in the AV mode or the P mode the maximum exposure time that the camera will allow is 1.5" and not the 30" that I would expect.

I have gone into the custom menu and enabled the 'make s lens available' and 'aperture ring permitted'

As soon as I switch to the 'kit zoom' the camera happily exposes to 30".

If I put those M42 lenses on any of my canon bodies the camera happily exposes to 30"

I am a professional cameraman with many years working with motion picture, film, digital etc.... but this one has me baffled. I feel like there has to be a way to achieve this exposure.

Using these older manual lenses is the best option for me as they will give me the best results. I would prefer not to use a zoom. (I cannot afford to have the lens move). The timelapse installation will be in place for 18 months. The camera is well housed, with a good battery system and timelapse controller.

Looking forward to any thoughts from the forum.

Thanks in advance,

Ben Ruffell
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Ben Ruffell

05-08-2008, 06:00 PM   #2
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Don't think M42 lenses work in av - correctly. Supposed to be used in manual. They definetly don't work in program. Put camera in manual exposure/manual focus and hit green button to stop lens down for correct exposure. You may have to "tweek" exposure because older Pentax lenses had a different motion than new ones. It will now go to 30".
thanks
barondla
05-08-2008, 06:04 PM   #3
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QuoteOriginally posted by ruff Quote
Hello,

I am new here and new to Pentax. I am not however new to photography. I have a question regarding exposure time while using manual lenses.

Shooting in the aperture priority mode with F11 and several stops of ND in front of the lens. I am shooting a long term timelapse of a construction project. I want an exposure time of about half a second in full sun in order to have good motion blur.

I would expect the camera to expose at half a second in full sun during the day, and up to a maximum of 30" at night.

When I attach an M42 mount lens via the official Pentax adaptor (either a zeiss or a pentax super takumer) in the AV mode or the P mode the maximum exposure time that the camera will allow is 1.5" and not the 30" that I would expect.

I have gone into the custom menu and enabled the 'make s lens available' and 'aperture ring permitted'

As soon as I switch to the 'kit zoom' the camera happily exposes to 30".

If I put those M42 lenses on any of my canon bodies the camera happily exposes to 30"

I am a professional cameraman with many years working with motion picture, film, digital etc.... but this one has me baffled. I feel like there has to be a way to achieve this exposure.

Using these older manual lenses is the best option for me as they will give me the best results. I would prefer not to use a zoom. (I cannot afford to have the lens move). The timelapse installation will be in place for 18 months. The camera is well housed, with a good battery system and timelapse controller.

Looking forward to any thoughts from the forum.

Thanks in advance,

Ben Ruffell
Cameraman
Ben Ruffell
I have found that once the light gets below the limitation of the metering that youo are "stuck" at the minimum calculatable exposure. I have hit this limit inadvertantly on several occasions. the best is to meter wide open, then count down the number of stops and adkust shutter time without metering, in manual mode.
05-08-2008, 06:56 PM   #4
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Thats interesting, thanks for the thoughtful replies.

The limitation of metering (on the nighttime exposures) coupled with the limitations of M42 lenses outside of manual control does appear to be a problem.

I find it very odd that the canon bodies don't have this problem.

As the camera is going to be in a weatherproof box for 18 months taking a picture every 15 minutes - I need an exposure that I can trust.

I guess a solution would be to add a modern pentax prime, such as the: smc PENTAX-DA 21mmF3.2AL Limited

Does anyone have any experience with this? Can you foresee any problems with the P mode?

Thanks,

Ben

05-08-2008, 07:11 PM   #5
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QuoteOriginally posted by ruff Quote
Thats interesting, thanks for the thoughtful replies.

The limitation of metering (on the nighttime exposures) coupled with the limitations of M42 lenses outside of manual control does appear to be a problem.

I find it very odd that the canon bodies don't have this problem.
I am not sure they don't you need to check the spec's for the light meter and sensitivity
QuoteQuote:

As the camera is going to be in a weatherproof box for 18 months taking a picture every 15 minutes - I need an exposure that I can trust.

I guess a solution would be to add a modern pentax prime, such as the: smc PENTAX-DA 21mmF3.2AL Limited

Does anyone have any experience with this? Can you foresee any problems with the P mode?

Thanks,

Ben
It is interesting that you ae going to be taking so many photo's especially at night, what is your ultimate goal, it seems to be very expensive to put an SLR in a box for this long. Are you externally powering the unit. how much memory, because you will have over 500 photos, (96 per day in fact) if they are not JPEG you will be servicing the box every day. I would be worried about image registration, i.e. the ability to return it exactly to the same view.
05-08-2008, 07:44 PM   #6
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This is a timelapse of a construction project. A building going up, from nothing to completion. (I will be filming the rest of the construction and the whole thing will be edited together for a corporate video).

It is expensive, but it's all thought out with contracts and suitable charge out. I am at the testing phase now. I plan to install the box in two weeks. I have a weatherproof fiber glass box with camera mount, timelapse controller, lithium battery (which powers the camera for one month), and a solar panel attached that keeps the battery charged. 2GB card. The camera has a usb cable attached so that I can connect a laptop every seven days and download without disturbing the setup.

The attraction with nighttime shots is that the lighting is quite often the most consistent, and when composited together the results can be stunning.

I am considering the fact that it may be a metering limitation and that no camera is able to reliably meter for more than a few seconds.

Shooting high resolution jpegs with manual white balance. The quality is far greater than HD and when composited together will offer room for reframing and virtual camera moves and so on. If the camera does move, it is a relatively easy fix in post. It should be ok as I am set back in a semi covered balcony 2 stories up, with an engineer making a mount to hold the box from four corners.

Something to think about... my local dealer just offered me that lens for NZ$1040... but I don't want to drop that kind of cash without knowing if it will solve the problem.

Regards,

Ben
05-08-2008, 08:39 PM   #7
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I noticed the same limitation about a week ago. In stop-down mode, the meter would simply not assign a shutter duration greater than 1.5 sec.

While it is possible to work around this, your options are definitely more limited if you need to use non-KA mount lenses and the process is automated. Your best option might be to pick up a KA lens. Unless you need a wide-angle at less than 24mm, there should be a fairly good selection of quality used glass available.

Good luck

Steve
05-08-2008, 08:48 PM   #8
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You could go with a second hand "A" lens; might be less expensive. They are manual focus but allow for using the exposure automation to the full extent just like DA lenses.

05-08-2008, 09:28 PM   #9
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I am glad that I am not the only one who has experienced this!

I require a 35mm equivalent of 32mm... that led me to the Pentax DA 21mm. I can get one from B&H for US$477 inc shipping. (Unfortunately I do not have the time to hunt for a second hand lens).

I see that with that lens you have the option of a 49mm filter size when using the hood, and a 43mm when no hood is used. I am inclined to go with the hood, and 49mm ND filters screwed in. I cannot find a photo of this hood, and with limited time... has anyone tried one or two of the 49mm filters successfully without vignetting?

Emails are into Pentax USA hoping for an answer on the exposure time questions. I will hold off buying until I hear back from them.

The knowledge of this forum is very appreciated.

Regards,

Ben
05-20-2008, 03:02 PM   #10
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Well here is the Pentax answer:

Dear Sir,

Thank you for contacting Pentax.

Manual lenses should really not be used in P mode. As for metering in AV or M, we are aware that there is an issue with metering at higher f stops on some manual lenses.
Unfortunately, we do not have a solution for this a this time, but the issue has been escalated to our engineers.
Obviously, it is not desireable, but If you use the lens in manual you can set the shutter speed correctly.

If you are in need of further assistance, please respond to this email or call our technical support center at 800-877-0155.

Sincerely,
Dorian B.
Pentax Imaging Technical Support

I am waiting on the DA 21mm to arrive... hopefully that will solve my issues.

Cheers,

Ben
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