Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Here are two exposures. The first uses an ISO of 3200 the second uses 64 - 6 stops of underexposure. I used 1/50 @F5.6 for both. I probably should have used a fixed white balance for both, since the severely underexposed shot, in this light, has a reddish cast.

All I did in post was to advance the exposure slider in Lr by 5 stops, then I opened up the shadows with the shadow slider, and added a bit of color and luminance noise reduction.

ISO 3200

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ISO 64

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Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

[quote=TriX]

Of the 20 different respondents at the time I made my blanket statement, not a one indicated that they had an appreciation for what ISO invariance is. And I was very clear that it only applies to certain cameras - Sony and Nikon to start - that are ISO invariant.

mwsilvers Loc: Central New Jersey

Of course some of us were responding to your first post where this subject had not yet come up. And while I do revisit threads to look at other posts, I don't necessarily read ever post in a 6 -page plus thread. If you had brought up the subject of ISO invariance in your first post perhaps this thread would have proceeded very differently

Tomcat5133 Loc: Gladwyne PA

Yes ISO has grain. But the ability to shoot in any lighting situation is really great. My Sony a7s II can do that.
I went to art basil in Miami friday and shot with the bridge camera RX10 III. I set manual to what I liked.
The lighting was all over the place spots full overheads lighting for art exhibition. So I set my wheel in
back to ISO and dialed in an adjustment with one finger. I know when I have to much ISO. This camera is
2.4-4 and the video was for publicity video I am going to publish for promotion.
We now have great low light camera's from all our camera makers. It is great to work with.
I think it used to be Tri X that we used in desperation years ago.
I like the duller more monochromatic look that is more of the Sony image. I pick a look up front.
PS this is just a screen grab.

BebuLamar

So with all the talk about ISO invarriance you mean that one should only use the base ISO regardless of lighting condition. If it's dark then it would be underexposed but one can simply bring it up in PP. So there is no need for high ISO is that what we talk about?

Rongnongno Loc: FL

There is LESS need. Use the DR at base ISO works only if the DR can cover the correct exposure. The limit depends on the camera capabilities.

The why high ISO did not introduce invariant sensor because too many folks go onto high ISO w/o a need. High ISO has a high price: noise, color shift, limited DR. All the 'I need it is dark area' does not hold much water. How did photographer take tack sharp images in a basket ball game with the same lighting? They did not have a gazillion ISO to chose from. What they had were sharp bright lenses (a disappearing commodity) an often wide open aperture to fully exploit their lenses AND experience.

High ISO has made most of us lazy.

BebuLamar

However you do it is not my argument but I do have the want and need to give an image very little exposure and get a decent image. That is relative high shutter speed, small aperture and low lighting and yet good exposure. I would not argue whether you do it in post or set the high ISO when taking the picture.
Doing so does make the quality suffer but much less than if I were to use high speed film. I never use high speed film in the old days because the penalty for graininess is too severe for moderate speed gain. With digital I find the penalty is much less.

Rongnongno Loc: FL

Sorry, I am confused.

This applies ONLY to raw shooting.
Shooting using DR does not prevent anyone from using high speed or low aperture or a combination of both - As long as the camera limitations in DR are not exceeded -. The noise when using a camera this way is negligible compared to a high ISO setting.

Invariant sensors (we need to get used to this)
I tested the Nikon D500 (invariant). At base ISO (100) I can under expose 5 stops. This means I could use 1/4000s instead of a normal exposure at 1/125 and still have an exploitable image if my need is to 'freeze the action'. Aperture is in the same range (I usually shoot for the lens* 'sweet spot') so instead of f8/11 I could shoot with a smaller aperture (but i will never do that due the aperture cost).

Older sensors
High ISO seems to be the only solution yet DR still offers some latitude in PP that allows for reducing the noise at the time of capture. That latitude needs to be tested per camera for best results.

When using JPG
To achieve the same result I would have to use ISO 3200, S 1/4000 and f11 which introduces sensor noise in addition to compression artifacts. (Not to mention other drawbacks due to the file format)

-----
* Prime lenses

chrisg-optical Loc: New York, NY

Thanks I never gave that a thought but that is a great tool to keep in mind. This assumes shooting in NEF RAW right, which I always do? I did know under is better than over generally as blown highlights can never be recovered.

TriX Loc: Raleigh, NC

Gene, my statement does not imply that at all. My point was that with an ISO invariant Camera (which encompasses probably the majority of DSLRs in use today), in a low light environment, once you have used the fastest lens available (wide open), and you need a given shutter speed to freeze the action, then your only options are increasing the ISO or raising the brightness in post with the attendant increase in noise. Please give me credit for not making uninformed statements. Not only have I reread the article from which you excerpted the above illustration, I have read everything I can find on the subject, so please don’t presume I am uninformed. In fact, I think I may have a better grasp on the subject than many of its proponents here. Let me start with a quote directly from the article that you drew the illustration from:

“ISO invariance is not a measure of how good a particular camera or sensor is. It simply means that a lot of the exposure is generated with the image processor rather than in the sensor. It's simply a different approach to low light photography.

So while I do think ISO-less shooting is an exciting new technique for low light photographers (doesn't make a lick of difference for daytime photography), it's certainly not worth picking a camera simply based on its ISO-invariance.”

Now some comments and then a challenge:

First, there is nothing magic about ISO invariance. Effective ISO can be changed in-Camera by either amplifying the sensor output prior to the A/D, multiplying the digital output of the A/D by a constant or (more commonly) a combination of the two. It’s been suggested that the A/D reference voltage could also been changed, but to my knowledge, no one has demonstrated that is actually used by camera manufacturers. It should be noted that all the cameras I’m familiar with (including Nikon’s and Canons) use the multiplication by a constant in SW beyound ISO 1000 or so regardless of the method at lower ISOs. Given that, whether the multiplication is done in-Camera or in post, the result is the same - the noise is multiplied along with the signal. There is no difference as to whether this is done by an amplifier or multiplying the output of the A/D - the noise from the sensor and that inherent in the A/D due to digitizing error are multiplied the same amount. If the argument is that the amplifier adds noise, remember that we’re discusing a signal that has a dynamic range of about 12-13 bits (<80 dB) and low level amplifiers with a noise floor below 14bits are common - every $50 CD player has one. While there is an advantage (as pointed out in the referenced article) to doing the operation in post in that the operation can be selectively applied to portions of the image, the result is the same. The point being that the idea that the DR is magically improved by doing the operation in post doesn’t hold up. I think this misunderstanding derives from the well-known fact that DR decreases with increasing ISO as measured prior to post. What it ignores is that those curves never show what happens after post if you choose to underexpose and raise in post. Since the multiplication of the data is the same regardless where it’s done, there is no magic change in the DR. The noise and the signal are multiplied in the same way - just accomplished in a different place. If you read the above-referenced article, where both methods are compared, there is no clear-cut advantage in underexposing and raising the brightness later outside of the selective enhancement in post I mentioned.

Now for the challange. While I have seen your photos that were almost black raised 5 stops in post to a usable image, i’m More interested in some more typical exposures. How about you or Ron (or someone else) post the following: using an “ISO invariant Camera”, take a low light action shot (such as indoor sports) both at ISO 5000 (or whatever is the “correct” exposure) and 5 stops underexposed. Same shutter speed, same lens, same f stop - just a change in ISO. Bring the underexposed shot up in brightness in post to match the brightness of the “correctly exposed” shot and post the results. No noise reduction, no curves, nothing but a change to the gamma to make the brightness the same. I’ll look forward to seeing the results.

BebuLamar

You misunderstood me. When you asked do we need high ISO my answer is yes because I need to shoot in low light. The bottom line is I don't care whether I would shoot at ISO 100 and bring it up in post or shoot at ISO 6400. What I meant is that I do need the camera to be able to capture decent images at light level where the correct exposure would be at least ISO6400. I don't care whether I would shoot it at ISO 100 and increase the exposure by 6 stop in post or I shoot it at ISO 6400 to begin with.

Rongnongno Loc: FL

As I said, I was confused.

My apologies.

Michael71

Higher ISO is for situations where low shutter speeds are not a good option. This can be true even when using a tripod, when going from ISO 100 to 400 or 800 will stop the motion of the subject (for example, an iris, which I would shoot at f16, but the breeze has come up.) When you no longer need the high ISO it is simple to change it.

rehess Loc: South Bend, Indiana, USA

The question we've not addressed, perhaps on purpose, is what are you going to do after taking the picture. I choose to use the JPEGs created by the camera, so I'm interested in the quality of JPEGs created at higher ISO levels; most of you don't seem to use those, but either approach should be acceptable, and the existence of people like me {and other users, from grandparents capturing grandkids in organized leagues to reporters covering the Olympics} will partly explain the focus on continually improving high ISO results.

PhotoKurtz Loc: Carterville, IL

High ISO can save the day. 5:00 am one day in June I arrived at an air race to meet with media and hosts. Off to the west was a totally unplanned full moon. No tripod. I braced my 100-400 zoom on the hood of the truck. Shutter speeds were wayyyy to slow to deal with. When I cranked up to 6400, f13 and found 1/400th. (Canon 7D)

Lots of grain, but for the event coffee mug things worked well. #22 is my buddy from the day before.

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