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01-29-2024, 07:50 AM - 1 Like   #76
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QuoteOriginally posted by Kevin B123 Quote
If I have physically set the lens aperture on the lens aperture ring to say f11, and I obtain a correct exposure it cannot use a wide open aperture?
It can, because the camera will use a shutter speed that gives you a correct exposure.

For lenses like the "K" or M series (and later series when the aperture ring is not on the "A" position), the aperture is not communicated to the camera. If you try to use Av mode the camera will set a shutter speed basis the amount of light coming through the lens, and will not stop the lens down during capture.

You need to use Manual mode to get the camera to stop the lens down. You can use the green button metering method to get the camera to set the shutter speed, and you will have correct exposure at the selected aperture.

All this applies to every DSLR by Pentax except the K-3 III models.

You can try this for yourself. In Av mode take a picture with your M 50/1.7 set at 1.7. Now change aperture ring to f22 and take the same picture. You should have two identical exposures at the same shutter speed/ISO

01-29-2024, 07:52 AM - 1 Like   #77
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QuoteOriginally posted by ehrwien Quote
I guess it will not work on the K-1 (I)?
QuoteOriginally posted by Lord Lucan Quote
It does, to my surprise.
It wont work on either.

Last edited by pschlute; 01-29-2024 at 08:40 AM.
01-29-2024, 07:55 AM - 1 Like   #78
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QuoteOriginally posted by JoelA Quote
Works for M42 also! And beyond Takumars
Av mode has always worked fine on M42 lenses, because unlike K and M lenses, they do not employ open aperture metering. The blades close as you turn the aperture ring

Last edited by pschlute; 01-29-2024 at 08:40 AM.
02-01-2024, 07:19 AM - 1 Like   #79
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QuoteOriginally posted by pschlute Quote
In Av mode the camera will give a correct exposure by adjusting shutter speed, but always uses wide open aperture.
Correct, and I came to the wrong conclusion after doing an unscientific test. I have since done a better test.

I would have assumed that on a DSLR like the K-1 in Av mode the aperture of a manual (M-series) lens would have closed to the value set on its ring when the shutter was pressed, even if the exposure was going to be wrong. Not so, it remains fully open. In fact I have just discovered that the DoF preview lever does not close it down either. In AV mode however the exposure is correct because the camera sets an appropriate shutter speed anyway.

These are two pictures taken with a K-1 with a 50mm M series F1.4 lens. The camera is in AV mode and the lens aperture ring is set to F1.4 and F11. (Interesting that the exif data reports F0). It is focussed on the tree, but the same shallow depth of field and the same degree of out-of-focus of the bush in the centre background shows that the aperture must have been F1.4 for both, and the shutter speed for both was 1/800. It was a very dull day. I must admit the F1.4 one looks half a stop darker, I can't explain that, no PP except to convert to jpeg for posting..

The heron is metal BTW and is meant to deter real ones from the pond




02-01-2024, 08:54 AM   #80
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QuoteOriginally posted by Lord Lucan Quote
I would have assumed that on a DSLR like the K-1 in Av mode the aperture of a manual (M-series) lens would have closed to the value set on its ring when the shutter was pressed
This is all down to the "crippled" K-mount that was created around 1997. Prior to that, the metal guide on all K and M series lenses would tell the camera what aperture it had been set to. So on my 1991 Z-1 film camera I could use Av mode perfectly without resorting to stop-down metering. After 1997 this was no longer the case and only the A-series (and later) lenses would communicate their f stop to the camera, and only if the aperture ring was set to "A". The communication was handled completely differently through the mount connector pins. For this reason if you want a K or M lens to stop down you must use Manual mode.

QuoteOriginally posted by Lord Lucan Quote
Interesting that the exif data reports F0
The camera has no clue what it is.

QuoteOriginally posted by Lord Lucan Quote
The heron is metal BTW and is meant to deter real ones from the pond
Do you feed it old nuts and bolts ?
02-01-2024, 09:37 AM   #81
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QuoteOriginally posted by Lord Lucan Quote
Correct, and I came to the wrong conclusion after doing an unscientific test. I have since done a better test.

I would have assumed that on a DSLR like the K-1 in Av mode the aperture of a manual (M-series) lens would have closed to the value set on its ring when the shutter was pressed, even if the exposure was going to be wrong. Not so, it remains fully open. In fact I have just discovered that the DoF preview lever does not close it down either. In AV mode however the exposure is correct because the camera sets an appropriate shutter speed anyway.

These are two pictures taken with a K-1 with a 50mm M series F1.4 lens. The camera is in AV mode and the lens aperture ring is set to F1.4 and F11. (Interesting that the exif data reports F0). It is focussed on the tree, but the same shallow depth of field and the same degree of out-of-focus of the bush in the centre background shows that the aperture must have been F1.4 for both, and the shutter speed for both was 1/800. It was a very dull day. I must admit the F1.4 one looks half a stop darker, I can't explain that, no PP except to convert to jpeg for posting..

The heron is metal BTW and is meant to deter real ones from the pond

It's obvious from the second photo that it wasn't taken at f/11 - the depth of field is far too shallow.

I made this same mistake when I first got an M 50/1.7 for using on my K200D. I though I was stopping down because I had the aperture ring on the lens set to something other than wide open and couldn't figure out why my DoF was still too shallow. This lead to extensive some reading up on using manual lenses on a Pentax DSLR.

The camera has no way of knowing what the aperture on the lens is set to as the lens doesn't tell it and the aperture is held wide open.

If you want to shoot in Av with a K-mount lens without an A setting on the aperture ring then you'll need to do it on a non-Pentax mirrorless camera.
02-01-2024, 11:54 AM   #82
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QuoteOriginally posted by Jonathan Mac Quote
If you want to shoot in Av with a K-mount lens without an A setting on the aperture ring then you'll need to do it on a non-Pentax mirrorless camera.
Not quite true. The K-3 III has automated the stop-down metering so you can use Av mode seamlessly. I expect the K-1 III will follow suit.

Further.....how exactly will any other "non-Pentax mirrorless camera" recognise the aperture ring setting ?

02-01-2024, 12:22 PM   #83
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QuoteOriginally posted by pschlute Quote
You can try this for yourself. In Av mode take a picture with your M 50/1.7 set at 1.7. Now change aperture ring to f22 and take the same picture. You should have two identical exposures at the same shutter speed/ISO
This is what I misunderstood, I forgot that f22 (fully closed) is the default and the camera opens it up from there, so setting f11 is of no benefit.

QuoteOriginally posted by pschlute Quote
The K-3 III has automated the stop-down metering so you can use Av mode seamlessly. I expect the K-1 III will follow suit.
This is what I thought we had, but apparently not. I shall continue to use manual and the green button.
02-04-2024, 11:36 AM - 4 Likes   #84
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Sometimes the discovered function is a frightening experience!

One time the four-way controller on my K-1 stopped working. I couldn't change the AF points or use the drive, WB, etc. controls. Turning the camera on and off didn't help! Pulling the battery didn't fix it! Had water gotten into the four-way buttons? Was the mainboard on the verge of death?

Nope... it was an undiscovered function. For the first time in 6 years of heavy use, I'd accidentally activated the the "Lock" button on the left side of the lens mount.

I LOL now but at the time I was sweating bullets!
02-04-2024, 08:04 PM   #85
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My surprise was a missing feature I'd used on the K-5: the much newer K-70 didn't have dust alert. I could sort of simulate it, but without that red dot I always have to remember to invert but not reverse. Or reverse but not invert? Whatever.
02-05-2024, 03:30 AM   #86
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QuoteOriginally posted by tibbitts Quote
My surprise was a missing feature I'd used on the K-5: the much newer K-70 didn't have dust alert. I could sort of simulate it, but without that red dot I always have to remember to invert but not reverse. Or reverse but not invert? Whatever.
The improved dust removal system and the specialised coating for the sensor do seem to make "dust bunnies" less of a problem on the newer cameras.
Whilst bemoaning the omission of a feature ... finding myself "all set up and ready to go" with my then new KP on a tripod in the field ... the discovery that there was no facility for I/R remote was a disappointment
02-05-2024, 10:11 AM - 1 Like   #87
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On the K-1 (at least) that you can take a picture with recording set to jpeg only, but then choose to save the RAW version as well. This is done by going to the review of the image and then pressing the AE-L button. There is a small pictogram on the review image that suggests this. I guess this is available only as long as the image is in the buffer.
02-05-2024, 07:15 PM   #88
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QuoteOriginally posted by kypfer Quote
The improved dust removal system and the specialised coating for the sensor do seem to make "dust bunnies" less of a problem on the newer cameras.
Whilst bemoaning the omission of a feature ... finding myself "all set up and ready to go" with my then new KP on a tripod in the field ... the discovery that there was no facility for I/R remote was a disappointment
I didn't know that about the KP.

Actually the K-70 has the old unimproved shake-the-camera sensor cleaning vs. the older-but-more sophisticated K-5 system, but I knew that when I bought it. I didn't know it wouldn't have the handy feature to (easily, obviously) show me where the dust bunnies were like on the K-5. Does the K3iii have the better K-5 dust removal system and the dust alert with the red dot on the LCD?
02-08-2024, 05:21 PM   #89
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I don't have to set the interval timer to include the time of the shot AND the time between shot. Ex: a 30secs expo. with 10 secs between shots, I used to set 40secs. I found to just set the time between shots, 10secs. 1 less thing to reset, now I just set how many shots.
02-09-2024, 03:55 PM   #90
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QuoteOriginally posted by Lord Lucan Quote
On the K-1 (at least) that you can take a picture with recording set to jpeg only, but then choose to save the RAW version as well. This is done by going to the review of the image and then pressing the AE-L button. There is a small pictogram on the review image that suggests this. I guess this is available only as long as the image is in the buffer.
You can do this on the K30 and K500 too (except it is the +/- button). Also while the image is in the buffer you can preview the effect of changing White Balance, Custom Image or Digital Filters. Anyone know anything else you can do with the raw image in the buffer?

Last edited by Andy58; 02-10-2024 at 02:17 PM. Reason: missing word
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