Optimal ASA setting for CFV (and other sensors)

[peterbkk]

Here's another question that I have been mulling over now that I am back in action with my CFV.

Assuming all else is equal (i.e. no need to handhold with a fast shutter speed in low light), for optimal image quality, what is the best ASA setting for the CFV back (or any digital back / digital camera)?

Is it always the lowest setting? 50 ASA? 100 ASA?

Does any ASA setting faster than the lowest setting use amplification (gain) to achieve that ASA rating? Any amplification reduces image quality somewhat, right? Is all amplification bad?

Does the reduction in quality start immediately? Is 100 ASA noticably worse than 50 ASA?

Should we all be using our CFVs (on a tripod) at the lowest ASA setting? Or are the amplication effects not noticable until several steps up?

What's the basic math and physics behind all this?

Regards
Peter

 

[lorenz]

well, I mostly shoot with ISO50, but the difference between ISO100 and ISO50 is compared to image quality not so bad. You can use it as well, I think. Bether never use ISO200/400.

But also, I think, the image quality depends so much on digital postprocess. Some people really work proper on taking picture but loose a lot of quality in post. It's the same question as example if you show a slide in a projector with strong light and good lens or in a bad one. you also see the difference if you know both.

Also, the image quality in labor depends so much on paper, developer etc, and you see all difference.

Some people just don't know how important it is to learn the digital process as good as we learned photography on field or laboratory.

justmy2cents, regards (sorry for this useless english)

 

[polypal]

Hello Lorenz,

The English is not so useless and what is more you are absolutely right about handling digital files.
Thanks for your contribution on this matter.

Paul

 

[fotografz]

Optimal ISO for CFV?

Usually, (not always), the lower ISO is the native optimal setting on most any digital camera.

Some older digital backs like the original Kodak ProBack allowed only ISO 100. There were no other choices. Since the CFV essentially uses the same sensor with some improvements, it suggests that the ISO 100 actual image quality is probably is just as good as 50 ... and depending on conditions, maybe better. I noticed this to be true when shooting in the studio with strobes, but it would be interesting to also test this with ambient lighting.

Some 35mm type DSLRs offer an ISO range from 100 to 1600 or 3200 as main selections, but can be expanded on both ends to both lower and higher ISOs via menu selections. Often, both the lower (ISO 25 and 50) and the higher expansions are compromises. ISO 25, 50 (and for some cameras 100,) are there for use when we want to use larger apertures in brighter light ... but do not necessarily improve IQ, or actually may degrade it a bit. I know this to be true from direct experience for both Canon and Nikon digital cameras known for their higher ISO capabilities ... ISO 25 and 50 are worse than 100.

I do not agree that ISO 200 and 400 on the CFV are to be avoided. IMO, this is a creative decision or is dictated by prevailing conditions even when on a tripod ... such as light levels, subject movement, etc. In fact, often the only place I use 50 and 100 is in the studio where I am in control of powerful strobes and need to get the aperture settings to their optimal DOF without too much lens diffraction affecting the IQ.

Because the apertures for most of 500 series lenses are a bit slower than what we are used to with 35mm cameras, ISO 200 and 400 are valuable options if care is taken to expose the Histogram to the right so there is no need to increase the EV in Phocus or Flexcolor. Phocus is becoming a powerful software tool but still introduces serious compromises when trying to lift underexposed images.

Obviously, all of this depends on your intent. If it is to make massive blow-ups beyond say 26" X 26" then other factors have to be considered.

 

[peterbkk]

Some people just don't know how important it is to learn the digital process as good as we learned photography on field or laboratory.

justmy2cents, regards (sorry for this useless english)

Your English is fine. Very understandable.

Digital does tend to push us towards a more hit-or-miss approach to photography. I know that I used to take more care when I only had 12 shots per roll, a complex roll change process and expensive processing costs. With a 4Mb card in the CFV I have 120 shots so I'll just flip the exposure up and down a few settings and sort them out when I get home. Fortunately, I have good grounding from slide film to start with close to the right settings...

Regards
Peter

 

[michaelhcothran]

If memory serves me on this thread, I believe I read somewhere (when I bought my CFV a year ago) that there is no quality difference between 50 & 100 settings on the CFV, but that the 50 setting serves only as a "neutral density" filter, allowing you to use a slower shutter speed when desired.

I believe that some of the Canon's are similar.

Someone correct me if I'm wrong on this.

Michael H. Cothran

 

[peterbkk]

If memory serves me on this thread, I believe I read somewhere (when I bought my CFV a year ago) that there is no quality difference between 50 & 100 settings on the CFV, but that the 50 setting serves only as a "neutral density" filter, allowing you to use a slower shutter speed when desired.
Michael H. Cothran

After some experimentation and careful note-taking, I have come to the conclusion that the right settings for me are:

CFV back: 100 ASA
205FCC body: 25 ASA

I can not see any difference between images taken with the back set to 50 or 100 ASA (and only a very small difference with the back set at 200 ASA).

With the body set 2 stops slower ASA than the back, I can use the Zone metering system and place the zone spots at the same settings as I've always used (with Fujichrome 100) and get a broad coverage of the histogram up to the lighter (right-hand) end of the spectrum.

Regards
Peter

 

[jotloob]

After some experimentation and careful note-taking, I have come to the conclusion that the right settings for me are:
CFV back: 100 ASA
205FCC body: 25 ASA

Peter
Thanks for your figures . Yesterday , I checked my settings again as well .
If I set :
CFV BACK = 100ASA
203FE body = 50ASA I do not get a complete histogram . Only about 70%-80% as mentioned earlier .
CFV BACK = 100ASA
203FE body = 25ASA , then I get a complete histogram .
Funny , although there is a complete fstop between the two settings , I receive a "green light" exposure for both settings .

Jürgen

 

[blowupster]

25asa is realy low. Usualy I use 100 asa. Last week to tried 50 asa (velvia) for portraits.
Hard to work outside: limited flash power (D40). Low speed and to open lens for short distance field.

With my digital M8, the lowest asa is 160 (in fact it's a 200 asa) with 1.4 lens, it's realy smart.

With the new 400(800-1600)asa TMY with a 110mm/2.0 is smarter.
For "paysage" pictures with tripod 25 asa is not a problem but crop factor is.

 

[peterbkk]

Funny , although there is a complete fstop between the two settings , I receive a "green light" exposure for both settings .

Earlier today I took about 30 indoor photos of my daughter dressed to go out to a party. On about 3, beacuse of ailing batteries, the bounce flash did not fire at all. I do remember hearing a "under exposure" beep from the back. Those 3 images are almost completely dark. But they all still have a "green light" both in the CFV and in Phocus.

Then I realised that I had "default approval" set to green rather than auto. Problem solved.

Regards
Peter

 

[jotloob]

But they all still have a "green light" both in the CFV and in Phocus.
Then I realised that I had "default approval" set to green rather than auto. Problem solved.
Regards
Peter

Thanks Peter

I checked that setting and corrected it to "auto" now .

Jürgen

 

[Pavel]

I personally feel that there is more difference in the developer used rather than iso - up to about iso 400. Tmax 400 for example exposed well ( I like a slightly thin negative because I scan) has grain about the same as any traditional emulsion at iso 100. Of course I'm thinking of only Black and White ... but in any color slide film iso 100 is about it as far as speed and with color print film ... I have also found that past iso 100 one gives up much too much quality past 100 as well.

Of course if you like lower contrast and grain ... 800 is an option then.

 

[jotloob]

... but in any color slide film iso 100 is about it as far as speed and with color print film ... I have also found that past iso 100 one gives up much too much quality past 100 as well.
Of course if you like lower contrast and grain ... 800 is an option then.

Pavel

Have a look to the new KODAK EKTAR 100 .
It is not a slide film , but KODAK promises the world's finest grain .
I have no experience with that film yet , because I received the 35mm and also the 120 just yesterday morning .
View attachment 1095

 

[vandevantersh]

Have a look to the new KODAK EKTAR 100 .
It is not a slide film , but KODAK promises the world's finest grain .
I have no experience with that film yet , because I received the 35mm and also the 120 just yesterday morning .
********
I just ordered Ektar 100, 35mm and 120. From reviews that I have read, the film exposes better at ISO 80 or even lower. I will be interested in your results.

Steve

 

[jotloob]

Steve

My experience with film is , that the given sensitivity was never as told .
Therefore , as you say , I will set my meter rather to ISO 80 than to 100 .