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Forum: Pentax K-30 & K-50 19 Hours Ago  
Should I expect solenoid failure on a K-50
Posted By m42man
Replies: 30
Views: 976
Well, that's quite interesting.

I wonder if a poll asking whether a) failed after inactivity, b) failed after regular use, and c) non-failure after inactivity is worth doing?

Anyone know how to do a poll?
Forum: Pentax K-30 & K-50 3 Days Ago  
Should I expect solenoid failure on a K-50
Posted By m42man
Replies: 30
Views: 976
Here's an interesting question:

Has anyone any experience of a K-30, K-50 or K-500 which has been left unused for 6 months or more, and which doesn't now suffer from aperture solenoid failure?
Forum: Pentax K-30 & K-50 3 Days Ago  
Should I expect solenoid failure on a K-50
Posted By m42man
Replies: 30
Views: 976
Note that you don't have to necessarily lose autofocus. There are plenty of decent lenses which are autofocus AND have aperture rings.

If you do use a manual focus lens, you might like to try Catch-in-Focus - just hold the shutter button down while you adjust focus, and when the camera judges focus has been reached, the shutter will fire. I find this works well for focal lengths of 50mm and greater.

Note also that you can use Av mode with an afflicted (i.e. bad solenoid) camera, when you use the aperture ring. You do need to use appropriate exposure compensation if you aren't shooting wide open though, in order to get correct exposure.
Forum: Pentax K-70 08-05-2022, 02:09 PM  
K-70 Underexposed report
Posted By m42man
Replies: 17
Views: 820
Yes, the above only applies to K-mount lenses with aperture rings.
Forum: Pentax K-70 08-05-2022, 12:57 PM  
K-70 Underexposed report
Posted By m42man
Replies: 17
Views: 820
Well, using Av mode with an afflicted K30/50/70 etc. means that the camera meters with the lens wide open, and you have to perform the calculation for the exposure at the set aperture - and that means that you need to know the wide-open (i.e. max) aperture of the lens, because the exposure at set aperture is calculated relative to the wide-open aperture.

Since many (most) zooms have a variable wide-open aperture, you're never certain what the wide-open f-number is. So you're stuffed, and you probably just resort to using the green button and M mode...

---------- Post added 5th Aug 2022 at 09:06 PM ----------



If your K-30 has a good solenoid, then if you operate in Av mode with a lens whose aperture ring is set to a value (i.e. not "A"), the camera will refuse to stop down, and will take the shot with the lens at wide-open - so, regardless of the aperture set by the ring. You'll get a correctly exposed photo, but always with a wide-open lens.

But if you try that with a K-30 that has a failed solenoid, the camera will stop down in Av mode - but will still expose as if the lens was wide-open. That's why you need to compensate (by the number of stops relative to wide-open) if you want correct exposure.

Does your K-30 have a failed solenoid?
Forum: Pentax K-70 08-03-2022, 02:48 AM  
K-70 Underexposed report
Posted By m42man
Replies: 17
Views: 820
Not necessarily. Assuming a hard fault, the camera can be relied upon to attempt to always stop down - arrested only by an aperture-ring setting. This means Av mode will work as before - BUT won't expose correctly (unless the lens is wide open) because it has no knowledge of the operating aperture.

However, all you have to do for correct exposure is do what the camera would normally do - i.e. calculate the correct exposure for the set aperture and get the camera to expose accordingly. And you do this using Exposure Compensation. So, for an f2 lens set to f4, just use +2EV compensation, and the correct exposure will result. This is usually more accurate than the green button in M-mode, as it emulates normal operation.

Assuming it's convenient to operate at a single given aperture setting, this means you can shoot away just as you would normally in Av mode.

Not so useful if the lens is a variable (max) aperture zoom though...
Forum: General Photography 07-24-2022, 12:11 PM  
Setting IBIS on a manual zoom with SCIENCE!
Posted By m42man
Replies: 7
Views: 726
Greater than the actual FL is indeed fine, as long as it's less than by a factor of 2. I definitely agree about trying to minimise camera shake, but you do lose a bit of reduction if you set a zoom lens to minimum FL - the "safe" method above is worthwhile - unless you want to shoot at minimum FL a lot of the time.
Forum: Pentax SLR Lens Discussion 07-24-2022, 11:29 AM  
is there any cheap,SR compatible 100-400 lens?
Posted By m42man
Replies: 25
Views: 988
Yes, I should have read the article - so you'd only choose the value of 75 if you weren't anticipating using FLs below 37.5mm (or at least were happy with blur magnification that would result if you did). Still, hardly "optimal".
Forum: General Photography 07-24-2022, 11:10 AM  
Setting IBIS on a manual zoom with SCIENCE!
Posted By m42man
Replies: 7
Views: 726
I've not read the article, but if 75 is its recommended value for a 28-200mm zoom, then the tool is clearly wrong.

Values greater than twice the actual focal length will result in blur magnification - clearly undesirable.

Use instead 2*min*max/(min+max), which is safe for all zoom ratios, or (min+max)/2 (but only for zoom ratios up to 3:1).
Forum: Pentax SLR Lens Discussion 07-24-2022, 11:02 AM  
is there any cheap,SR compatible 100-400 lens?
Posted By m42man
Replies: 25
Views: 988
Hmm, the linked post states, from the article it's referring to: "IBIS for a 28-200 (per this paper) should be set to 75mm for optimal effect". This is bunkum, and should be ignored.

If you input a value which is greater than twice the actual focal length, the camera will move the sensor such that you end up with more blur than with SR turned off.

There are two formulae you can use though:

1. This equalises the blur reduction at each end of the zoom range, and is intrinsically safe (i.e. will never magnify blur): 2*min*max/(min+max)

2. This equalises the amount of blur at each end of the zoom range, so is better at the long end - but is only safe for zoom ratios up to 3:1 - just take the average, i.e. (min+max)/2

There's another, more sophisticated formula which optimises for random zoom settings, and this can be found over at dpr. You end up with a value somewhere between the two above, but be careful, as some (large) zoom ratios will end up with an unsafe value.
Forum: Pentax DSLR Discussion 07-19-2022, 01:26 AM  
At a crossroads if I should repair and new lenses vs new body.
Posted By m42man
Replies: 25
Views: 979
You have several options:

1. Get K-mount lenses which have aperture rings, and use as prescribed. And/or an M42 adaptor, and some M42 lenses (Takumars are especially rewarding).

2. Fix the problem yourself, using a known-good solenoid (white). Plenty of tutorials online. Has the advantage over a "professional" repair, which will usually involve replacing a bad solenoid with a similar (green) one which will fail, all at great expense.

3. Abandon the K-500 and replace with a camera which doesn't suffer from the solenoid problem - which would be the pre-K-30 models (K100, K10, K200, K20, K-m/K2000, K-7, K-x, K-r), or the K-5 series, K-3 series, KP. But note that the lesser/earlier cameras (K100 especially) may well have been cannibalized and their sought-after white solenoid replaced with a green one. Note that the "entry-level" K-S1, K-S2 and K-70 all use a green solenoid.
Forum: Winners' Showcase 07-07-2022, 01:10 AM  
June, 2022 Runner-up: The way out
Posted By m42man
Replies: 42
Views: 127
I would like to nominate this photo
Forum: Pentax K-30 & K-50 06-23-2022, 01:17 PM  
K-30 / K-50 Aperture Block Failue - Repair Solution available
Posted By m42man
Replies: 1,041
Views: 197,385
I got one too! It's good!
Forum: Winners' Showcase 06-07-2022, 12:44 PM  
May, 2022 Winner: Turnip Rock
Posted By m42man
Replies: 73
Views: 212
I would like to nominate this photo
Forum: Monthly Photo Contests 05-08-2022, 01:57 AM  
Hazy
Posted By m42man
Replies: 23
Views: 273
I would like to nominate this photo
Forum: Pentax K-30 & K-50 05-02-2022, 04:25 AM  
K-30 / K-50 Aperture Block Failue - Repair Solution available
Posted By m42man
Replies: 1,041
Views: 197,385
Know the feeling - I've seen tidier rats' nests! (But, then, I'm a bit of a cheapskate anyway.)

That's a good tip (!) for a new iron - I still soldier on with an Antex from the '60s. It's about time I got a new one...
Forum: Monthly Photo Contests 04-08-2022, 01:33 AM  
Eraser Nose
Posted By m42man
Replies: 7
Views: 97
I would like to nominate this photo
Forum: Pentax Compact Cameras 03-22-2022, 08:50 AM  
Do you want another bridge camera from Pentax ?
Posted By m42man
Replies: 21
Views: 1,499
Well, do note that the Fuji HS50 has a 42x manual zoom! Quite unusual though.
Forum: Monthly Photo Contests 03-08-2022, 12:56 AM  
Vaureal Falls, Anticosti Island
Posted By m42man
Replies: 14
Views: 91
I would like to nominate this photo
Forum: Pentax SLR Lens Discussion 02-25-2022, 03:17 AM  
More of my unscientific tests. Pentax-M SMC F1.7 50mm vs. Pentax-M SMC F4 Macro 50mm
Posted By m42man
Replies: 15
Views: 1,057
You may find this interesting...

Nifty 50 Shootout : ERPhotoReview
Forum: Pentax SLR Lens Discussion 02-11-2022, 04:54 AM  
Another help me choose a long lens
Posted By m42man
Replies: 61
Views: 2,741
Well, I think I'd agree. Though, if you already own a decent DSLR, maybe the cost of a long lens vs a superzoom camera becomes relevant.

The superzoom has the advantages of far less bulk, plus the ability to stabilise the frame seen through the EVF - which facilitates accurate focussing on the intended subject. Though use of a stabilised lens with the DSLR would have the same advantage...

---------- Post added 11th Feb 2022 at 12:10 PM ----------



Do note that sharpening a Raw image is standard practice where an AA filter has been employed. Plus, the K-3 will have sharpened its Raw image to provide the jpeg output.

The Canon's sensor is truly tiny (1/2.3"), compared with the K-3's APSC - and would need good lighting to be able to offer any competition in terms of noise (at similar apertures). Also, though the Tamron is stellar value for money, there are better-performing long lenses available (at a price!). But I think the K-3 crop is slightly superior, regardless.

For me, it comes down to bulk and viewfinder stabilisation, I suppose. (Not that I use long focal lengths much anyway.)
Forum: Pentax SLR Lens Discussion 02-11-2022, 12:54 AM  
Another help me choose a long lens
Posted By m42man
Replies: 61
Views: 2,741
Here's an example of a superzoom bridge camera vs DSLR:

Cameras are Canon SX50hs (12MP @ 1200mm FF-equiv., f6.5) and Pentax K-3 (24MP with Tamron's 70-300mm f4-5.6 @ 300mm, 450mm FF-equiv., f8).

The Canon is on the left - a lightly sharpened image from Raw; the K-3 is an in-camera jpeg (probably set to fine sharpening), and both images are of course crops:
Forum: Pentax DSLR Discussion 01-30-2022, 04:57 AM  
Which batteries do you hate, and why (AA NiMH vs. D-LI90 vs. D-LI109)?
Posted By m42man
Replies: 32
Views: 4,221
I'm surprised no-one's mentioned Energiser Ultimate Lithium AA primary cells - great for when on vacation, no need for chargers, can be changed for alkaline AAs bought locally if they run out of charge. They last far, far longer than alkaline or NimH in my venerable K-m (K2000) (and were supplied with the camera from new). Expensive though, at around 5 per 4, but offer a relatively stable/high cell voltage compared to the AA alternatives.
Forum: Pentax K-30 & K-50 01-04-2022, 04:08 AM  
Dead Again
Posted By m42man
Replies: 17
Views: 1,253
Hopefully you don't mean manual focus, as there are loads of suitable autofocus lenses out there which have aperture rings (some of them very good).

And you don't have to use Manual Mode and the Green Button - afflicted cameras work in Av mode with these lenses. BUT, you have to use Exposure Compensation to accommodate the set aperture. So, for instance, if you have a nice 50mm f2 lens, and you want to take photos at f4 (because that's where it becomes really sharp), just set Av mode and give it exposure compensation of +2 EV. No need for stop-down metering once set up.

Not so handy if you're using a variable-aperture zoom though...
Forum: Pentax DSLR Discussion 12-26-2021, 01:00 AM  
How does AF decide which way to go
Posted By m42man
Replies: 36
Views: 1,262
Exactly!

Just to add: regarding CDAF, if the lens is well-known, the quality of the bokeh in front of and behind the current focus plane can be used to decide direction (Panasonic).
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