[madbrain]

Yes. The Sigma is a variable aperture lens and could be f4 wide open, but only f5.6 zoomed in.

Yes, I'm aware, but I was also switching back & forth between live view and viewfinder also each time I zoomed, and compared shutter speed at identical exposure & focal length each time.
I was getting shutter speeds between 1/30 and 1/60 and ISO 6400, with lens as wide open as possible. The shutter speed was sometimes equal for VF and LV, and other times faster in VF. Difference was never more than a factor of 2.

[pjsaure]

Does a polarizer which theoretically looses around 1-3/4 full stops (between 1-1/2 to maximum 2), actually loose between 2-1/3 and 3-1/3 full stops? I doubt it. Unless, like one said, a DSLR camera will looses more light than a mirrorless camera. I tend to think it's both reasons, not only one.

You are right, it is not only the polarizer.

As some have said, it could also in part be due to the lens, as the f/ number only indicates the diameter of the physical aperture in the lens, not the light that is transmitted to the sensor. Different glass, different coatings, let more or less light in. The light that passes through is measured in T stops, which is typically not specified for stills camera lenses. You might find that information on something like DXOmark though.

It could also be due to a difference in the ISO scale of each camera. ISO 100 does not mean exactly the same thing to different cameras, especially when you consider different brands. It seems to be quite common to have 1/3 to a 1/2 stop variation here.

[clackers]

I'm bowing out of this thread, the lack of scientific rigour has me thinking I'm reading a discussion in DPR!

[alvaro_garcia]

I'm bowing out of this thread, the lack of scientific rigour has me thinking I'm reading a discussion in DPR!

Could that light loss (opening the diaphragm and slowing down the shutter speed) on the Pentax over the Nikon be measured scientifically by giving exactly how much % of that is due to each of the following factors:

1. Circular polarizer (and depending on the angle and strength of the effect)?
2. Different lenses?
3. Sensor size?
4. Less efficiency of lightness on DSLRs over mirrorless cameras?
5. Different image processors / in-camera mettering processing / algorithms?
6. Different program line modes?
7. EV setting?
8. Others?

---

Last edited by alvaro_garcia; 05-07-2018 at 06:25 AM.

[pschlute]

mmmmmm....

Last time I used a handheld incident light meter, I dont recall it asking me what format i was taking the photograph on !

or lens

or dslr vs mirrorless

or processing technique

or "others"

Light is light. if you are getting different results with different cameras (formats), the most likely explanation is you are not metering the same area in each picture.

[normhead]

I miss my hand held light meter. I'm sure it is around somewhere but it stopped working in the 90s after a 30 year career. I'm sure if it still worked I'd be checking to see how many times I use the EV dial to get the exposure an incident reading would have given me right off the get go. A DSLR is like using a spot meter all the time.

Thses days with digital, no one cares much about how many test shots they waste getting the exposure the way they want. When each roll of 24 shots cost you 10 bucks for film and processing and you didn't see the results for a week, an incident light meter was the way to go. These days we all just chimp.

[ChristianRock]

So, does the CP affect that much the mettering? I read somewhere that this polarizer looses less than 2 stops of light.

f3.5 to f5.6 = 1-1/3 full stops, yeah?
And 1/160 to 1/320 = 1 full stop, yeah?
Total difference = 2-1/3 full stops.

But on the Nikon's 1/640 picture, the difference with the Pentax is 1 full stop more:
Total difference = 3-1/3 full stops.

Does a polarizer which theoretically looses around 1-1/2 full stops (between 1-1/4 to maximum 1-3/4), actually loose between 2-1/3 and 3-1/3 full stops? I doubt it. Unless, like someone said, a DSLR camera will looses more light than a mirrorless camera. I tend to think it's both reasons, not only one.[COLOR="Silver"]

You also need to take into consideration that your Nikon is underexposing by about a step compared to the K-1 pictures. Look at the rock wall comparing the two pictures and you will see what I am talking about.

It has been said here many times but if you take the polarizer off and make the exposures look the same in the histogram, the exposure elements (shutter speed, ISO, aperture) will be very similar, with a 1/3 to 2/3 of a step not uncommon due to differences in T-Stop (light transmission) and your own perception (it's hard to see a 1/3 stop difference or even 1/2 step, that is why most lens manufacturers didn't even bothered with half steps in their aperture rings back in the film days).

[Canada_Rockies]

All of this discussion is getting tedious. The OP has too many variables in his question. I don't understand anyone saying that a polarizer will pass more than 1/4 the light coming in. For the 60 years or so I have been using cameras, a polarizer is 2 stops light loss. That doesn't change for circular/non circular. Circular Polarizers are to solve problems with the AF system and other sensor/mirror problems due to the light splitting.

The answer to exposure problems is Manual Exposure mode and your brain. I still use this table with the M 400 because most of the time I get a better exposure than with the fancy meter in the K-3 which will only give me center weighted exposures with non-A lenses.

Do this simple math to get accurate exposures. It used to be printed on a delightful little piece of paper that came in your box of film. It still works. Adjust shutter and aperture to equivalent exposures for special treatments. For example, with the DA 12-24, I never use an aperture smaller than f/11 and prefer f/8 whenever possible to avoid diffraction errors. On bright sand below: ISO 100 = 1/100 @ f/22 = 1/200 @ f/16 = 1/400 @ f/8 ...

Shutter speed = 1/ISO
Subject extremely bright (sandy beach) f/22
Subject lit by direct sun f/16
Subject lit by sidelight f/11
Subject lit by backlight f/8
Partially cloudy add one stop
Bright cloudy add two stops
Dark cloudy add three stops
Polarizer: add 2 stops
#2 Dark Orange filter (one of my favourites in film days) add 1.5 stops

Each camera manufacturer has its own idea of correct exposure. Pentax tends (correctly in my opinion) to underexpose by about 1/2 stop and always has. This was correct for slide film and remains correct for sensors. If you blow out the highlights, there is no way to get it back. You can increase the brightness in printing and post processing with very little loss in the darks until you are underexposed more than 1 stop.

If you have a tricky subject, meter the darkest area with detail you want to keep and reduce two stops or spot meter the brightest you want to keep and add two stops.

[UncleVanya]

I'm going to take a stab at this.

Nikon Coolpix A vs. K-1 - what's different:
Sensor
Lens (T stops)
Metering Logic
Metering Sensors
Maximum F stop
Filter

What's the same:
Both take pictures
Both have a 28mm FOV using the lens in question.

Which factors affect the exposure at the time of taking:
Sensor
Lens (T Stops) (1/2 to 1/3 stop likely)
Metering Logic (1 stop roughly)
Metering Sensors (?)
Maximum F stop
Filter (2 stops)
ISO
Shutter Speed
Aperture

Honestly I think the OP is very confused and looking for help understanding what is essentially a non-existent issue. I have seen several questions asking about the faster lens and I think it has been said a few times but I will repeat it. At any f stop the only differences between the lenses are the T stops (1/2 to 1/3 stops likely) so the Nikon at f/2.8 and the Zeiss at f/2.8 are the same the Zeiss isn't any faster once you stop down to f/2.8 - it offers the option to go wide open which could help you take pictures in lower light but it does not act any differently once you stop down. The same goes for the full frame sensor - the extra sensitivity and the ability to shoot at higher ISO with less noise means you can use it in lower light - but if you shoot in good light and have the ISO the same - there is no actual gain to be had in overall exposure. Yes you might see less noise but that's not the measurement being discussed. Lastly, Nikon has often underexposed ISO 100 in the past. Tests by lots of reviewers have shown this. I do not know for sure if the Coolpix A does but it could. It isn't important in the long run.

Set both cameras to manual and do a series of exposures at various ISO's and shutter speeds and apertures and see what the overall results are. Make sure both are filterless.

[Tan68]

I'm going to take a stab at this.

...

Alvaro has gotten advice that varies a lot
He will have to decide who is giving him reasonable advice

[alvaro_garcia]

Alvaro has gotten advice that varies a lot
He will have to decide who is giving him reasonable advice

Yes I did get. These days a bit busy with medical checks, hospitals... As soon as I get home in couple of days I'll test again without CP filters on these three:

- Nikon Coolpix A
- Canon 7D
- Pentax K1

[madbrain]

Yes I did get. These days a bit busy with medical checks, hospitals... As soon as I get home in couple of days I'll test again without CP filters on these three:

- Nikon Coolpix A
- Canon 7D
- Pentax K1

Since you have many different cameras, it may be worth getting lens adapters if you want to do serious comparisons, and use the exact same lens.
Pentax lenses can be mounted on Canon, though you will only be able to set aperture if the lens has an aperture ring . Not sure about mount them on Nikon bodies.
AFAIK there is no adapter that allows AF with any Pentax lens on foreign bodies, or allows AF with foreign lenses on Pentax bodies.

[UncleVanya]

Since you have many different cameras, it may be worth getting lens adapters if you want to do serious comparisons, and use the exact same lens.
Pentax lenses can be mounted on Canon, though you will only be able to set aperture if the lens has an aperture ring . Not sure about mount them on Nikon bodies.
AFAIK there is no adapter that allows AF with any Pentax lens on foreign bodies, or allows AF with foreign lenses on Pentax bodies.

The Coolpix A is a fixed lens camera similar to the Ricoh GR.

[alvaro_garcia]

The Coolpix A is a fixed lens camera similar to the Ricoh GR.

Yes, but different colour rendition (Nikon more "neutral", Pentax more "cold").

[normhead]

Yes, but different colour rendition (Nikon more "neutral", Pentax more "cold").

We use a Nikon 130 AW and we find the opposite. I really dislike the Nikon colour rendering, as do many others here. I guess it's whatever you get used to.