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05-24-2020, 04:33 PM   #1
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Astrophoto anomaly

A problem I've had for a while has been actually finding something bright enough to focus on (and framing in general) when using the default "Astrophoto" User-Mode, both on my K-70 and my KP. Tonight, by accident, I "strayed" from "Astrophoto" to one of the "Normal" modes, Av or something, and suddenly found that there's a much brighter image on the LiveView screen, making life so much easier. It's grainy and noisy, certainly, but at least there's something to see


So, has anyone else had experience of this and, if so, is there any more obvious work-around other than set up in Av (or whatever) then change into "Astrophoto" to actually make the exposure(s)? I'm assuming here that the "Astrophoto" setting is actually advantageous

05-24-2020, 11:33 PM   #2
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I notice this with flash. When its dark and i use live view at f4 1/180 the screen is dark because the flash isnt firing naturally. I turn the shutter to like 5 seconds and live view uses iso to brighten to what the shot would look like at 5second shutter w/o flash. It cant accumulate 5 seconds of light when the view is cycling much faster. If you moved the camera the view wouldnt change, and when it did, it would have 5 secs of motion blur.

Wish i new an easy way to switch it on and off. At least i only use it for critical focus when on a tripod with stationary subjects.
05-25-2020, 12:28 AM - 2 Likes   #3
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Evening, I have a friend who shoots with a K70 and we both shoot astro a fair amount. So, let me provide some background first so that all of this makes sense.

A year ago, I saw that a local camera shot was sponsoring a 3 day astro class for $99. Friday evening 2 hour class, Saturday night on location class 5pm to midnight and Sunday afternoon post processing session. The instructor shoots for Arizona Highways. She starts off saying, that she doesn't know why half of us are taking the class since we have as much experience as she, but to pair up with folks with the same camera brand, who are new to this. Anyway, Saturday evening we're on location and about 11pm a guy drives up and sets up his stuff right next to me - he just got off of work. Turns out that he just picked up his K70 the week before. He had read the manual twice and had a 28/f2.8 lens, and had shot the first 20 images of his life with a dslr. So, we started talking since we were the only two who shot Pentax. He shot several frames and they were beginner ok frames. By that time some folks left and we moved to a better location. I pulled out my gps astrotracer and mounted my 18-35/f1.8 lens on his body, calibrated the setup and he shot a wonderful milky way over picket post mountain image. He was ecstatic. We have been shooting together ever since.

I shoot with a K1, so I looked up "Astrophoto" User-Mode in the K70 manual. It really didn't provide any of the setting parameters, and he never uses it. That's as much as I know about it. However, having said that - this is how we shoot and it works quite well. You haven't said if you are using the gps astrotracer and if you are doing milky way with landscapes or deep sky. So, I'll assume no gps for this.
  • Switch to "M"anual or "B"ulb mode - This way you will have complete control over the parameters you set. The light meter is useless at night, so the other modes will try to evaluate the scene based on no information, so just by pass them. The main difference between Manual and Bulb mode is that with Manual mode you can only set the shutter duration up to 30 seconds. With Bulb mode you can exceed 30 seconds - take it up to minutes if you wish.
  • For framing, we crank the ISO up to something high 10,000 and above, aperture wide open, with a shutter speed of about 1 second. Take a look at the image on the rear screen and adjust as needed (be it landscape or just stars). If you don't see anything, increase the shutter speed, until you see something. You can also check focus here.
  • For Focusing, (put the body in manual focusing) find something bright in the sky, enable LiveView and zoom in to 16x, then use the arrow keys <>^v to get the bright object into the rear monitor. Adjust the focus until it is nice and sharp. Take another frame to check everything out.
You should be ready to go now.

We usually start out at ISO 800 to ISO 1600, wide open aperture (f1.8, f2, f2.8) depending on the lens. With ISO 800 you will get a bit more color in the milky way. We have gone as low as ISO 400 with good results. ISO 800 seems to be optimal on the K70 (which kicks in the Accelerator Chip at ISO ~630 which will help with noise). For a shutter speed, you can use two different approaches:
  • 200 Rule - Take the focal length you are shooting at 200/focal length = the shutter speed in seconds. 200/18 = 11 seconds
  • I like to use this website ---- Night Sky Photography Shutter Speed Calculator – With the K70, the crop factor = 1.5, megapixel =24, focal length = (your lens), pixel tolerance = (I use anything between 4 and 10, the smaller - the sharper the stars will be). This will provide 3 shutter speeds, I just take the largest value. So for 1.5; 24; 18; 4 provides 11.3 seconds or just 11 seconds.
_____________________________

Focusing alternative methods.
  • During the day - focus on something say 1/2 mile away, and tape the focus ring on the lens down. Make sure that you are in manual focusing.
  • Illuminate something far away with a flashlight, or place the flashlight on something and walk a far distance away and focus the camera.


Last edited by interested_observer; 05-25-2020 at 12:36 AM.
05-25-2020, 01:07 AM   #4
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QuoteOriginally posted by interested_observer Quote
I shoot with a K1, so I looked up "Astrophoto" User-Mode in the K70 manual. It really didn't provide any of the setting parameters, and he never uses it. That's as much as I know about it. However, having said that - this is how we shoot and it works quite well. You haven't said if you are using the gps astrotracer and if you are doing milky way with landscapes or deep sky. So, I'll assume no gps for this.
  • Switch to "M"anual or "B"ulb mode - This way you will have complete control over the parameters you set. The light meter is useless at night, so the other modes will try to evaluate the scene based on no information, so just by pass them. The main difference between Manual and Bulb mode is that with Manual mode you can only set the shutter duration up to 30 seconds. With Bulb mode you can exceed 30 seconds - take it up to minutes if you wish.
  • For framing, we crank the ISO up to something high 10,000 and above, aperture wide open, with a shutter speed of about 1 second. Take a look at the image on the rear screen and adjust as needed (be it landscape or just stars). If you don't see anything, increase the shutter speed, until you see something. You can also check focus here.
  • For Focusing, (put the body in manual focusing) find something bright in the sky, enable LiveView and zoom in to 16x, then use the arrow keys <>^v to get the bright object into the rear monitor. Adjust the focus until it is nice and sharp. Take another frame to check everything out.
You should be ready to go now.

Thanks ... this is more or less what I've now figured out ... what I'm really disappointed about (again) is the lack of detail regarding the default "Astrophoto" mode, much hyped by Pentax as being a "unique" feature yet nowhere does there seem to be any instruction on how to use it to advantage. I've had my O-GPS1 since the beginning of the year and whenever social circumstances, the moon and the weather have permitted I've tried to get out, only to struggle with what I'd (obviously wrongly) assumed was the best combination of settings for the job


Surprisingly, I have managed to make some acceptable (to me) images, both with and without the GPS, simply by literally "flying blind" ... I'm looking forward to exploiting my new-found knowledge

05-25-2020, 02:46 AM   #5
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QuoteOriginally posted by kypfer Quote
Thanks ... this is more or less what I've now figured out ... what I'm really disappointed about (again) is the lack of detail regarding the default "Astrophoto" mode, much hyped by Pentax as being a "unique" feature yet nowhere does there seem to be any instruction on how to use it to advantage. I've had my O-GPS1 since the beginning of the year and whenever social circumstances, the moon and the weather have permitted I've tried to get out, only to struggle with what I'd (obviously wrongly) assumed was the best combination of settings for the jobSurprisingly, I have managed to make some acceptable (to me) images, both with and without the GPS, simply by literally "flying blind" ... I'm looking forward to exploiting my new-found knowledge
I only have a K-3 and as far as I am aware I don't have a astrophoto mode, therefore I am just guessing here.
The problem I usually encounter when using LV for star but mainly moon photography is, that the LV image is much too bright no matter my actual exposure settings because LV doesn't give you a reliable preview of your image when you are outside a certain exposure range, it's main purpose is to let you focus, compose and set your exposure with the help of your histogram but it is not a actual preview of what your image will look like.

So when I take a picture of the moon, LV usually shows an image that is so bright I can't see any details on the moon surface to focus on.
-So I either have to focus on the edge of the moon and reach focus when the CAs of the lens reach a minimum,
-or when using a long enough lens you can use the workaround of using spot metering and position the moon in the centre of the frame, that way LV will tune down the brightness just enough to see the moon surface (the lens needs to be long enough to fill the greatest part of the spot metering area with the moon) -> after focusing you have to recompose your shot.

My guess is, that the astrophoto mode changes the LV settings in a way, that you can actually see details on the moon surface even when it is not positioned in the centre and without using spot metering.
You will still need to set your exposure settings yourself and for star photopraphy you can't see any details on the surface of the star anyway so this mode might just be useful for moon photography.
05-25-2020, 06:23 AM   #6
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QuoteOriginally posted by othar Quote
I only have a K-3 and as far as I am aware I don't have a astrophoto mode, therefore I am just guessing here.
The problem I usually encounter when using LV for star but mainly moon photography is, that the LV image is much too bright no matter my actual exposure settings because LV doesn't give you a reliable preview of your image when you are outside a certain exposure range, it's main purpose is to let you focus, compose and set your exposure with the help of your histogram but it is not a actual preview of what your image will look like.
Unfortunately guessing is what I've been doing for the last five months ... guessing that the default "Astrophoto" mode was actually the best tool for the job ... it may give very good results, dark backgrounds, correct colour stars, etc., but actually getting the camera into a configuration whereby "Astrophoto" can be used to advantage seems to be totally undocumented, much like some other "unique" features

Establishing a correct exposure for the moon is child's play in comparison, at least you can see the moon in LiveView, even if it is grossly overexposed - hint, use spot metering and centre the moon at full zoom in the viewfinder, then lock that meter reading Trying to photograph a constellation in a scenic setting using "Astrophoto" can be almost impossible ... everything is just too dark to make out any detail at all!

Hey ho - tonight's forecast is clear with moonset before midnight and light winds ... we'll have another go
05-25-2020, 07:15 AM   #7
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I thought astrophoto mode was meant to reduce brightness on the rear screen and avoid polluting the area with excess light after you already set up the shot.

05-25-2020, 08:27 AM   #8
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QuoteOriginally posted by UncleVanya Quote
I thought astrophoto mode was meant to reduce brightness on the rear screen and avoid polluting the area with excess light after you already set up the shot.


Nope - that's "Night Vision LCD Display".


"Astrophoto" is one of the default "User Modes" provided on (at least) the K-70 and KP to "Adjust the background black level and reproduce the colours of stars faithfully" - quoting from the KP user manual. Unfortunately, that's all it does say about it, no clues as to how to find the stars in the viewfinder or LiveView in the first place
05-25-2020, 08:36 AM   #9
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QuoteOriginally posted by kypfer Quote
Nope - that's "Night Vision LCD Display".


"Astrophoto" is one of the default "User Modes" provided on (at least) the K-70 and KP to "Adjust the background black level and reproduce the colours of stars faithfully" - quoting from the KP user manual. Unfortunately, that's all it does say about it, no clues as to how to find the stars in the viewfinder or LiveView in the first place
Ah... I misremembered the names. Good luck trying to get into on what it's supposed to do. I miss the old manuals that detailed all the options in intricate detail.
05-25-2020, 09:52 AM   #10
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I just checked Yvon Bourque's KP guidebook, and it only mentions Astrophoto once, only to say it's the default mode for user mode 3. No other comments.
05-25-2020, 10:45 AM   #11
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QuoteOriginally posted by kypfer Quote
Establishing a correct exposure for the moon is child's play in comparison, at least you can see the moon in LiveView, even if it is grossly overexposed - hint, use spot metering and centre the moon at full zoom in the viewfinder, then lock that meter reading Trying to photograph a constellation in a scenic setting using "Astrophoto" can be almost impossible ... everything is just too dark to make out any detail at all!
May I hint back that you should read the second and especially third paragraph before disregarding an admittedly highly speculative reply
05-25-2020, 12:37 PM   #12
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QuoteOriginally posted by othar Quote
May I hint back that you should read the second and especially third paragraph before disregarding an admittedly highly speculative reply


Sorry ... managed to skip through a little too fast

---------- Post added 05-25-20 at 12:44 PM ----------

QuoteOriginally posted by Apet-Sure Quote
I just checked Yvon Bourque's KP guidebook, and it only mentions Astrophoto once, only to say it's the default mode for user mode 3. No other comments.
Just as well I didn't "invest" in that publication ... I'd have been REALLY peeved.

How can someone market a publication as "Everything you need to know ... and then some" then totally skip a feature with no more than an acknowledgement of it's existence !?!?!

I'll bet he didn't cover "Digital Filters" in too much detail either!
05-25-2020, 02:34 PM   #13
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QuoteOriginally posted by kypfer Quote
I'll bet he didn't cover "Digital Filters" in too much detail either!
About 3-1/2 pages total in different sections, with examples of each. He does say that each of the digital filters have additional parameters, and he would be wasting space to cover in detail all of the possible permutations (I'm paraphrasing). He encourages the photographer to check out all the possibilities themselves. A reasonable approach IMO.

Last edited by Apet-Sure; 05-25-2020 at 02:45 PM.
05-25-2020, 07:56 PM   #14
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QuoteOriginally posted by kypfer Quote
Thanks ... this is more or less what I've now figured out ... what I'm really disappointed about (again) is the lack of detail regarding the default "Astrophoto" mode, much hyped by Pentax as being a "unique" feature yet nowhere does there seem to be any instruction on how to use it to advantage. I've had my O-GPS1 since the beginning of the year and whenever social circumstances, the moon and the weather have permitted I've tried to get out, only to struggle with what I'd (obviously wrongly) assumed was the best combination of settings for the job

Surprisingly, I have managed to make some acceptable (to me) images, both with and without the GPS, simply by literally "flying blind" ... I'm looking forward to exploiting my new-found knowledge
All the user modes like landscape, ..... , astrophoto, etc. are essentially best guesses that come standard on entry level camera of all brands. Astrophotography is the most unforgiving of these types of photography. It's pretty difficult, mainly because there is precious little light available. The best way is to essentially wing it the old fashion way with manual and bulb settings. Give the GPS astrotracing a try for the milky way - it works very well.

The Pentax astrotracing is especially good for milky way imaging, since it's pretty well suited for wide angle lenses. The longer the focal length lens you use, the shorter the duration. I can easily get about 5x the standard shot duration with astro tracing at 70 seconds as opposed to about 11 seconds. Going with a longer duration I get star trailing in the corners which is a function of optical distortion of wide angle lenses. Going with longer focal length lenses beyond 85mm, I haven't tried.

05-26-2020, 03:37 AM - 1 Like   #15
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QuoteOriginally posted by interested_observer Quote
All the user modes like landscape, ..... , astrophoto, etc. are essentially best guesses that come standard on entry level camera of all brands. Astrophotography is the most unforgiving of these types of photography. It's pretty difficult, mainly because there is precious little light available. The best way is to essentially wing it the old fashion way with manual and bulb settings. Give the GPS astrotracing a try for the milky way - it works very well.

The Pentax astrotracing is especially good for milky way imaging, since it's pretty well suited for wide angle lenses. The longer the focal length lens you use, the shorter the duration. I can easily get about 5x the standard shot duration with astro tracing at 70 seconds as opposed to about 11 seconds. Going with a longer duration I get star trailing in the corners which is a function of optical distortion of wide angle lenses. Going with longer focal length lenses beyond 85mm, I haven't tried.



Thanks for the insights - I use "Astrotracer" with my O-GPS1 on my K-70 very successfully, I was taking Milky Way shots only last evening. I've used this combination with my Sigma 70-200mm f/2.8 quite successfully up to 10 seconds at 200mm. As I become more familiar and confident with the equipment and start to run out of suitable subjects I'll "push the boundaries", but as yet I've more than enough wide-angle options to keep me busy when the sky's clear and the moon's not in the way


My original question referred to the use of the default "Astrophoto" user-mode, which seems to be totally undocumented. I've now figured out, on my K-70, if I click the mode-dial around one place, to "B", the LiveView screen brightens up considerably, allowing a degree of compositional assistance for aligning a constellation between trees, for example, or even to help ensure the whole constellation is in frame Just have to remember to return the mode-dial to "U3" before making the exposure and I'm good to go! The Astrophoto user-mode does work as described, allowing each star to show it's own colour, especially noticeable in a time-lapse star-trails exposure!


The KP works similarly in principle, but due to the "two-finger-shuffle" necessitated by the locking mode-dial it's not as easy to implement in the dark when the camera is tilted at an awkward angle on a tripod
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