[Gimbal]

I think we understand it the same way. What I discovered however is that the high light compression is applied to the RAW data, because I get different RAW histograms if I shoot ISO200 or ISO100 (-1ev) or ISO200 + highlight protection On.

Yes, I believe that was the case already on the K5, if memory serves. I never really used that function though, but perhaps I should, hm… At least in contrasty situations.

[filmamigo]

I don't think they're worth it Filmamigo, the maximum shutterspeed is typically about 1/1000s.

Most people will want to shoot outdoors at some time.

LOL, amazingly I shoot daylight fill-flash all the time at ISO 160 (Portra) and with leaf shutters that top out at 1/500 (Bronica.)

Having lower ISOs makes daylight fill easier and more flexible, especially to get large apertures and shallow DOF. The Pentax K-1 already goes lower than Portra (ISO 100) and it would be trivial for Pentax to add ISO 50 to a Pentax K-1 iii.

[xandos]

it would be trivial for Pentax to add ISO 50 to a Pentax K-1 iii

Can you explain? To me it seems like it would be very difficult to do so, except maybe by putting in a switchable ND filter (which still doesnt seem trivial). Sure, they could implement a amplification step with gain lower than 1, (compared to the usual amplification with gain >1 for when going to higher ISOs) but the dynamic range would take a huge hit. Am I missing something?

[Rondec]

LOL, amazingly I shoot daylight fill-flash all the time at ISO 160 (Portra) and with leaf shutters that top out at 1/500 (Bronica.)

Having lower ISOs makes daylight fill easier and more flexible, especially to get large apertures and shallow DOF. The Pentax K-1 already goes lower than Portra (ISO 100) and it would be trivial for Pentax to add ISO 50 to a Pentax K-1 iii.

I don't think it is that easy. To truly add an iso 50 setting, you would need to be able to expose a stop longer without blowing the highlights. My experience is that if I would bump the exposure compensation one stop, the highlights are completely unrecoverable. The D810 does have native iso 64 and has some bump in dynamic range to get there, but I think that it also has a much more expensive sensor to do that.

[beholder3]

I'd like the K-1 III to have a pink squirrel detector bell on top that goes "bing", whenever a red squirrel is closer than 10 meters.
I do consider this feature at least twice as important as the funny ideas mentioned on the last few pages.

Can we please brainstorm how to implement this?

[filmamigo]

xandos and Rondec,

Lower ISOs are provided by attenuating the output in some manner.

Nikon D750: ISO range 100-12800, expandable to 50-51200
Nikon D800: ISO range 100-6400, expandable to 50-25600
Canon 5D Mk IV: ISO range 100-32000, expandable to 50-102400

Results from these "Low" or 50 ISO settings look great and provide flexibility if you need to lose a stop without using an ND filter.

[biz-engineer]

The true limit of low ISO depends on how much reduction of sensor life time is allowed?. Having pixels saturated at the higher end of sensor supply may accelerate pixel aging, some of them die over time (dead pixels)?. Then there are other ways to lower the perceived ISO, for example speeding up the actual shutter speed vs what's being programmed and written in the exif... no one will even know , not even the test labs.

I have glasses that darken when exposed to the sun (photochromic glasses). Always wondered if the same would exist for cameras.

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Last edited by biz-engineer; 04-25-2019 at 08:31 AM.

[Wheatfield]

It was a tongue in cheek comment sir) not a serious claim about Norm.

Often the truth is best hidden in humour.

---------- Post added 04-25-19 at 05:22 PM ----------

Yeah, I think there's only two shutter manufacturers in the industry. Everyone buys from them.

The bigger the format, the bigger the shutter, the bigger the problem.

Perhaps, perhaps not. The bigger the format, the bigger and heavier the camera and the better the damping. I could stand a nickel on my 6x7's screen and trip the shutter without the coin falling over.

Biz-engineer points out because Pentax uses IBIS it can actually offset some of it, but obviously EFCS and Live View gets rid of it as well as mirror shock.

---------- Post added 04-25-19 at 05:28 PM ----------

But if you want to, you wouldn't be able to. You can't go any lower in ISO so you'd have to stop down affecting your depth of field or pack and reach for ND filters.

Leaf shutters are fine in a portrait studio where shutter speeds are irrelevant to the exposure, a lot of medium format lenses incorporated them.

No Canon, Nikon or Sony ILC bothers AFAIK.

My Ricoh GR II does have one, though.

Remember that the fastest speed of a focal plane shutter at present is only 3 stops faster than 1/1000 second.

---------- Post added 04-25-19 at 05:34 PM ----------

For long enough exposures, it's always possible to set the camera in bulb mode, pick-up a tree leaf (*) and manually place the leaf in front of the lens.

* the tree leaf should be large enough to fully cover the front element of the lens.

What you are talking about is an exposure method called flagging. It's a technique that I used frequently when shooting large format, and is still one I use from time to time as it allows the camera to stop vibrating prior to exposure.

[Larrymc]

I could stand a nickel on my 6x7's screen and trip the shutter without the coin falling over.

Hmmmm I just tried that with my K-3 with a dime and the dime never fell over even with a series of live view shots and non live view shots at 1/125 and 1/50 sec.

[clackers]

Remember that the fastest speed of a focal plane shutter at present is only 3 stops faster than 1/1000 second.

You can't possibly be giving this mad idea consideration, Wheatfield, you'd have to carry ND filters with you, Pentax would be laughed at by the other firms!

By the Sunny 16 rule, a focal plane shutter allows a f1.4 or f1.8 lens to shoot in sunlight.

[Wheatfield]

You can't possibly be giving this mad idea consideration, Wheatfield, you'd have to carry ND filters with you, Pentax would be laughed at by the other firms!

By the Sunny 16 rule, a focal plane shutter allows a f1.4 or f1.8 lens to shoot in sunlight.

Sure, and you would still have a focal plane shutter in the body. I think it’s a great idea. Combine a leaf shutter with live view, that would cure all the vibration issues, while not having the slow capture time of an electronic shutter.

---------- Post added 04-25-19 at 09:34 PM ----------

Hmmmm I just tried that with my K-3 with a dime and the dime never fell over even with a series of live view shots and non live view shots at 1/125 and 1/50 sec.

Have you heard a Pentax 6x7 shutter fire? One would think the world was ending from the racket. The camera had an undeserved reputation as a vibration monster based on how loud it was.

[xandos]

Lower ISOs are provided by attenuating the output in some manner.

A true lower ISO would require that either there is a lower input, or that the sensor has a capability of detecting lower signals than it currently does.


Here is how I understand digital cameras, please tell me where I go wrong: It seems to me that the current base ISO is the 'full' sensitivity of the sensor, ie, it records what it detects in its full single-pixel dynamic range (in case of an 8-bit sensor (for the sake of simplicity), the camera settings will be such that the brightest parts of the scene will register at near-max values (256). For an 8-bit sensor, the lowest values are ~1, and the dynamic range is basically given by this: the contrast between the highest and lowest value.
Now if we increase the ISO, we collect less light/lower values by changing the camera settings, and adjust by amplifying the signal. In doing so, we also amplify noise. Besides, if we use the full sensor range (0-256), we have 256-intensity steps per colour, but if we collect less light (lets say, for example, 128 steps) and amplify by a factor 2 to get back to the same values, we have less information, because we basically only have the even numbers from 0-256. We will have much less nuance in the colours. I don't entirely believe that this explanation is 100% correct, so if someone knows, please tell me.

If we want to do an attenuation step, we have a similar problem. For ISO 50, if our base or native iso of the sensor is 100, we'd have to set the camera up to massively overexpose and then de-amplify all sensor values. We run into a few problems: the sensor clips at maximum value of 256, so everything above is lost. So after de-amplification, if it was for example by a factor 2, there will be no brightnesses in the raw values above 128. Basically we lose the right part of the histogram. For the other values, we have rounding problems: for a deamplification of factor 2, each 2 histogram bins in the original is collapsed into a single bin post deamplification. So I think we should get very poor / no highlight recovery at all, and a hit in dynamic range.

[thibs]

Sure, and you would still have a focal plane shutter in the body. I think it’s a great idea. Combine a leaf shutter with live view, that would cure all the vibration issues, while not having the slow capture time of an electronic shutter.

Completely agree. I dont expect it but that would be genius.

[biz-engineer]

Happens to be something names EFCS that works for a wide range of shutter speeds. Why would anyone want to add another shutter? The trend with image sensors is faster frame rates and electronically controlled exposures. Some industrial sensors already feature global shutters (fully electronic).

[TwoUptons]

Have you heard a Pentax 6x7 shutter fire? One would think the world was ending from the racket. The camera had an undeserved reputation as a vibration monster based on how loud it was.

The 6x7 also has an instant-return mirror, something many of its competitors lacked.

So much of the noise and vibration happened after the picture was done, having no effect...

While all the Mamiya users were talking about how much quieter their cameras were, they were cranking back the mirror so they could see through the camera again...

But it is pretty freakin' loud...

-Eric