Iso/Av/Tv; Which to sacrifice?

[nail33]

I am somewhat of a newbie, which you can tell by this question. I have a

Canon xti with a Zenitar 16mm f/2.8, Canon 50mm f/1.4, and a Canon 100mm f/2.8

macro. From what I have read on various photo forums, most lenses have a sweet

spot around an aperture of 8-11. Given this, I strive to take normal pictures

with an Iso of 100, an aperture of around 8, and a shutter speed high enough to

prevent blur when handheld (roughly 1/focal length x 1.6 for crop factor). I

realize that these settings can only be used under ideal conditions. Using a

tripod takes the shutter speed out of this equation, provided the subject matter

is not moving, but I generally only like using the tripod when I am doing macro

photography. I have also noticed that I get red spots (noise I assume) in my

photos when viewed at 100% if I bump the Iso to high levels. So my question is:

when you take handheld photos, which of these parts of the equation (Iso/Av/Tv)

do you tend to sacrifice first, to get an acceptable photo? I assume when

handheld, you probably can not go with a slower shutter speed (Tv). I thank you

in advance for your advice.

[amol]

Arnold,

 

You have some nice prime lenses. My understanding is that you don't need to be at f/8-11 to be at the "sweet spot", for these lenses. (For macro work, you may need the f/8-11, but that's a special circumstance, and in that case a tripod is a good idea)

 

If you stop down 1-2 stops you should be good. So on a f/1.4, stopping down to f/2.8 or f/3.5 should be the "sweet spot". On a f/2.8 stopping down to f/3.5 or f/4.

 

The f/8-11 is usually in reference to variable aperture zooms. Like a f/4-5.6 (or 3.5-4.5), then a f/8 is a sweet spot. At least, that is my experience.

[Matt Laur]

Don't forget, Arnold, that when you do feel the need to boost the ISO, you need to "expose to the right" (see your histrogram). That high-ISO noise that you're seeing will be greatly reduced if you can keep more of your details out of the shadows.

[keith_lubow]

It is true that there are sweet spots on lenses, but that does not mean that the salty and sour spots are to be avoided. Using a lens at its sweet spot all the time sounds nice, but it is not worth the trouble for 95% of people. Aperture and shutter are your tools to achieve the "creative" effects you want, and sacrificing your control of them for a relatively unimportant technical concern is generally not worth it. Don't get so caught up in the minutiae of making the pix that you let them take the reins. The minutiae are simply tools and understandings that let you make the pix you want, not mandates that control what you "should" do.

 

Most who preach using a lens at its sweet spot are exacting commercial photographers who are using view cameras in a totally controlled environments. When you are using a view camera, then you don't sacrifice as much control by using a lens at its sweet spot, because you can get that control back in other ways using camera movements. These people also often have their images blown up to ginormous sizes, and often need a huge amount of detail and micro sharpness to satisfy their clients.

 

In short: Don't worry about it that much. It's good to understand it, but there is no reason to even have an adjustable diaphragm if you aren't going to use it.

 

Keith

[colinsouthern]

Arnold,

 

You're obviously up on the theory, but you've got a couple of things a bit skewed:

 

First up, the "sweet spot" for most lenses is around 3 stops down (from maximum aperture) - sometimes it'll be F8 / F11, sometimes it won't.

 

Second up, the "1/focal length" rule-of-thumb is a guide for minimising camera shake - to eliminate it altogether you need about 5 times that.

 

Third up, one of the things that makes the BIGGEST contribution to image sharpness is what's called "capture sharpening" - all 35mm Digital SLR cameras have what's called an anti-aliasing filter which deliberately introduces a degree of unsharpness into an image. The demosaicing process where colour information is extrapolated from the RBG coded information also introduces unsharpness - both of which need to be corrected in post-processing - and yet this is the step most often overlooked.

[photographicsafaris]

Generalising here, to make a picture, you want something to either stand out or other

areas to blend in from/to the background.

 

In order to make something stand out you generally use the aperture (certainly with the 2

canon lenses you have) this creates a small depth of field. This control input is through the

Aperture. (AV mode) Your secondary input is then shutter speed to get a sharp (motion)

image. Your third input being ISO to control the level of depth of field that you want at an

acceptable shutter speed.

 

In moving subjects you would use shutter speed to control the subjects movement, hence

shutter priority first (TV mode) Your secondary input may be Aperture which (generally)

defaults to wide open and in this case thirdly it would be ISO.

 

As a generalisation ISO is the quality control higher = worse quality, hence it is last input

but sort of acts as a reserve for shutter speed.

 

If you are using flash then you have a fourth control input, you control the freezing of

movement with the flash, and the power of the flash with the aperture, and to a lesser

extent depth of field. Shutter speed is reasonably insignificant to t

he subject,but has a controlling effect on the ambient lighting, here ISO is equally

important, as it also controls Ambient light levels and so it all becomes a four way

balancing act.

Oh and of course the power (duration) of the flash can also be controlled!

 

Hope that helps, remember that you pay good money to buy lenses that can be used with

wider apertures. and you are the one controlling the image, not a set of QC rules

 

Cheers G

[mark u]

Shoot basketball in the average high school gym, and you'll use high ISO with your 50mm f/1.4 almost wide open to get a high enough shutter speed to begin to stop subject motion. Even shooting surfers on a sunny day with a long telephoto, you might need to use ISO 200 with the lens wide open to get 1/4000th needed to freeze the spray more effectively. Sports shooters usually prefer to work at wide apertures to throw backgrounds out of focus and draw attention to the subject, while trying to use a suitable shutter speed (sometimes a slow one to show blurred motion intentionally), with ISO simply the consequence.

 

Shoot a landscape with high dynamic range and you'll want to ensure that you are using the camera's base ISO setting and a narrow enough aperture to have the entire capture appear sharp, with the shutter speed as a mere consequence unless you need to increase it because of wind blown trees and leaves - in which case you may try balancing with a couple of stops higher ISO. Shoot a waterfall and you may go even further, adding an ND filter to using low ISO and a narrow aperture to allow enough motion blur from using a longer shutter speed.

 

Shoot macro, and depth of field becomes a key choice. Some images can look spectacular shot wide open so that only part of the subject is sharp, surrounded by a wash of colour. In other cases, aperture will be chosen to maximise depth of field without losing too much sharpness to diffraction, remembering that effective aperture is usually roughly doubled at life size magnification. Since many macro lenses only use the more central parts of their elements at high magnification and narrow aperture, optical performance at higher aperture can be very different than using the lens for normal subjects - much less subject to various aberrations, at least so long as it is well corrected for close focus work. It is common to use flash to allow a low ISO for maximum image detail and to freeze camera shake which gets greatly magnified with macro work, requiring much higher shutter speeds than you might otherwise use for normal subjects.

 

Portrait work has some similar considerations to macro artistically, though fewer technical constraints.

 

Where you can work with a tripod and static subjects, digital image processing techniques such as HDR blending of bracketed captures and focus stacking can allow you to make a different set of compromises.

[kari v]

"I get red spots (noise I assume) in my photos when viewed at 100% if I bump the Iso to high levels."

 

XTi should be fine until ISO 800 *if* you don't underexpose (check out "expose to the right", it works at any ISO) and you can remove much of the remaining color noise in post. Also, viewing 100% crop is not always very meaningful, in net-size or print most of the noise will go away.

 

I don't know if you have a good copy of the Zenitar or not but the other two lenses produce excellent images at one (macro) or two stops (50mm) down and I wouldn't hesitate to use them wide open if need be. Yes, I'd even use the f1.4 wide open, I buy fast lenses to utilize the speed and shallow DoF. I find sharpness overrated in situations when I need something below f2.8.

[William Michael]

You are thinking about it all the wrong way around.

 

 

 

You are taking bald theory and attempting to make photographs with it.

 

 

 

You need to know the theory: what each of the three elements of exposure is responsible for and how any change affects it, and the other two.

 

 

 

That theory you carry with your camera, to the scene and ask yourself:

 

How do I want to capture this lightscape, and how can I use the theory I know to MANIPULATE it to be so?

 

 

You are not asking that question: you are asking for rules of theory to govern your artistic creation: that cannot work.

 

 

Some practical examples using your assumptions as `rules` and no offence is meant by my phraseology:

 

 

> most lenses have a sweet spot around an aperture of 8-11. <

 

 

I suggest all lenses have an (aperture) sweet spot where they are most sharp: it is usually two or three stops down from the largest aperture; a nice fact to know, and to use when you need the sharpest image, like copying a finely detailed manuscript: but that doesn`t mean wide open is not adequately sharp, or perhaps perfectly soft enough for some images.

 

 

> I strive to take normal pictures with an Iso of 100 <

 

 

Why? What if you would like a grainy ( = noisy in DSLR terms) sepia image, and little post processing to do?

 

 

> (at) an aperture of around 8 <

 

 

Why? if you want to have a shallow DoF (Depth of Field) on a tight head shot of a beautiful woman?

 

 

> and a shutter speed high enough to prevent blur when handheld (roughly 1/focal length x 1.6 for crop factor) <

 

 

Why? if you have a 200mm lens on an APS-C body and you wish to capture a cyclist riding slowly at 90 degrees to you across your lens and you want to `speed him up`: choose 1/100 sec or 1/80 sec and pan the shot?

 

 

> I realize that these settings can only be used under ideal conditions. <

 

 

You are waiting for `ideal conditions` to present themselves, before you hit the shutter button?

 

That`s OK if you are a photocopy machine or copying slides: you should be making photos!

 

 

> So my question is: when you take handheld photos, which of these parts of the equation (Iso/Av/Tv) do you tend to sacrifice first, to get an acceptable photo? <

 

 

The rule of sacrifice you seek does not exist: you must adapt the theory to each unique situation and control it, not let these `rules` control you.

 

 

If you need the flowing brook to be smooth, and to get that you need 1/8 sec, and you do not have a tripod, then you need to know how to adapt to get this `acceptable photo` you so much desire.

 

 

And do not say this is impossible: because it is indeed quite possible, with adequate practice and good technique and controlled breathing and knowing how to use your body as a support to shoot hand held at 1/8 sec with a normal lens and get at least 50% success, perhaps a better hit rate, if you are good at it.

 

 

Theory is fantastic to know.

 

I am the very first to stand up and suggest everyone should learn the theory.

 

But you learn theory, to allow YOU to MANIPULATE the RULES to suit the OUTCOMES that YOU WANT: you DO NOT let the theory dictate what you do.

 

WW

[nail33]

I would like to thank you all for the input to my question and I would like to respond to two of you in particular.

 

To Kari Vierimaa:

 

I did get a good copy of the Zenitar. This is truly a bargain lens. I wish more people that were on a budget would be advised to look into buying one. The distortion is not that bad on a small sensor camera, and if necessary, can be easily corrected during PP. My film camera is a Canon A1, so I am used to manual focus. Fortunately, the Zenitar is almost always set to infinity, as trying to manually focus with the xti is nearly impossible. I do not know why Canon could not have made the viewfinder as bright as the A1 and/or with some type of focus screen. I know there are after market products to solve this problem, but I do not think Canon should have let this become a problem to start with.

 

To William W (Retired):

 

I used the term, normal picture, to avoid getting a response like the one you made. Perhaps a quick shot would have been a better term to use. I used to take slides with my Canon A1 and would, as you say, manipulate the camera settings to achieve the results that I was looking for (i.e. nice bokeh in a portrait shot, the sense of speed in an action shot, etc.). There were, however, times when I did not have time to compose my shot properly so as to capture the moment. For those times, I would set the camera to an automatic mode and I was usually satisfied with the results (at least it was better than no shot at all). The drawback with film was that mistakes became costly and I had to be much more careful with the shots I took. Now that I have gone digital, I take a hundred times more pictures because they are basically free after the initial cost of the equipment. I take RAW pictures with my camera now that I do the developing (PP). Unfortunately, when using RAW, you can not use the full automatic setting on the camera. That is why I was asking for a general ideal setting for the camera, and which of the three settings I should adjust first (Iso/Av/Tv) for when I do not have time to properly compose the picture and manipulate the camera to get the results I would like. Sometimes a good picture is better than a perfect picture versus losing the moment and getting no picture at all. I am sorry for the misunderstanding. I still try to do everything you say when I can, but I need more experience with this camera to achieve the results I would like with every shot I take. Your response was very thoughtful and I appreciate it very much.

[William Michael]

 

 

 

 

 

 

 

 

 

 

 

 

 

>>> I used the term, normal picture, to avoid getting a response like the one you made. (. . . ) <<<

 

 

Ah! A Much Different Question.

 

 

Simple answer.

 

 

1. ISO goes first, just as it did with film.

 

 

That said, I am beginning from this premise, which I will describe practically:

 

 

I have my 5D in M mode 90% of the time, and with an EF 50mmF1.4, it would be at around F5.6 and ISO at 200, I am outside and the light is giving me 1/200s, I shoot RAW + JPEG L.

 

 

I am happy with those exposure parameters; but a if a `quick shot` comes up, I know I can go up or down at least 1 stop in both Av and Tv without even thinking or flinching: that gives me a 4 stop range.

 

 

After that 4 stop range is exercised I will sacrifice ISO for that quick shot: IF I do not have time to think and compose the exposure with detailed control.

 

 

And, If I do not have time to think, I will sacrifice ISO right up to ISO3200, and if I had 6400 I would go there too

.

 

This was the very first thing I practiced when I first got my 20D to quickly change the ISO with my left index finger, whilst not taking my eye away from the viewfinder.

 

 

IMO, the ability to change the ISO, and so quickly and easily, is one of the great benefits of the digital capture: and a benefit which is not praised that much, but rather seen by many as `I have to avoid the noise`.

 

 

It was a lot more difficult with a 36 roll of Tri X loaded, and half way through exposing the roll in the camera, I made a decision to push it to ASA1600 and then later had to `guess` where the middle of the film was, and in the darkroom cut it and develop two, half roll accordingly, one normal and one pushed two stops! (points like this are not recognized, by many, I think) .

 

 

 

2. After ISO I will (most likely) sacrifice Aperture in ALL circumstances. (Hence my `ranting` always about the value of fast lenses, they extend the capacity enormously)

 

 

But the decision to kill Av requires a bit of quick on the feet thinking: what lens do I have? what DoF do I need? But generally I think it best to get the main subject crisp and movement free and to hell with the DoF.

 

 

In this regard, I think like a photojournalist, not what some think a photojournalist is now, I mean like a `newspaper photographer`.

 

 

3. Lastly, again speaking `almost always`, but with the same caveat that I would think a bit on my feet, I would sacrifice Shutter Speed.

 

 

But I do have in place slow shutter skills (i.e. I have practiced the techniques I outlined earlier, re the brook).

 

 

I will attempt the shot (and have done so) right down to 1 sec exposure Hand Held, if needed: with digital there is very little to lose!

 

 

>>> That is why I was asking for a general ideal setting for the camera, and which of the three settings I should adjust first (Iso/Av/Tv) for when I do not have time to properly compose the picture and manipulate the camera to get the results I would like. <<<

 

 

You have probably gleaned that my method is to use M Mode, nearly always, and be very quick with the dials.

 

 

 

So if your question heads towards: `which AUTOMATIC MODE would you first use for a quick shot?` . . .

 

 

I am really at a loss, because I do not work that way, but at a pinch, I would use Tv and set 1/50s or 1/60s with a 50mm on 5D. BUT I would still need to control the ISO MANUALLY.

 

 

 

Expanding:

 

 

 

When I got my 20D I practiced the procedure of changing ISO, Av and Tv whilst in M Mode, for about six months.

 

 

Really: six months; until I could do it literally, with my eyes closed just counting the clicks, much like practicing piano scales with your eyes closed and someone calling out `stop` and you have to name the note your finger is on.

 

 

(I would play games just taking pictures of anything as I walked around, guessing the EV and setting the camera before bringing up to my eye, expecting that it was F8 at 1/125, etc)

 

 

 

After this specific practice, (and other `getting to know the Canon system` things: Canon was a new camera range to me also), I believed I was ready to shoot my first Wedding with digital, and then I was an assistant only, (AKA `second shooter`), even though I have covered Weddings with film for about 30 years.

 

 

Getting the dexterity and using M mode is easy, it is just plain boring doing the practice, just like E major, which is the scale I dislike most: it is not rocket science, just a simple discipline so that is why I made up games to do it: try it, it is fun, well almost fun!.

 

 

 

>>> Sometimes a good picture is better than a perfect picture versus losing the moment and getting no picture at all. <<<

 

Not `Sometimes` but `Every time `: a `reasonable` picture is better than no picture, especially where emotion is concerned: Agree 100%.

 

 

 

>>> I am sorry for the misunderstanding. <<<

 

No need to apologize: it is the problem we have when communicating with the written word only. I obviously interpreted the question was written by a less experienced photographer.

 

[ASIDE: It is interesting that yours is the type of personality that (seemingly) took no offence at my response based on the assumption that you had very little practical experience and had just been reading the theory: others might have been offended . . . and perhaps not taken the time and effort to re detail the question so specifically. ]

 

IMO this is a very insightful question and I have gained much from sitting and thinking and composing my words for the last 40 minutes answering it: thank you for that experience.

 

This question goes right to the premise of being prepared, for that `quick shot`, as you term it and being prepared enough for the possibility to turn the `quick shot` into that amazing capture that others say: `WOW! how did you get that? `the Capa shot`, if you will.

 

Guys such as Capa didn`t` just do it: their camera was an extension of their brain, they knew exactly what was where, every second: and they honed that skill until thinking just went from the eye to the hands, and the brain was bypassed, much like we breathe.

 

It was thoughtful of you to respond with the detail and clarification: look at it this way you got two answers for the one question!

 

WW

 

 

 

 

 

[keith_lubow]

My general rule of thumb in these situation is to sacrifice shutter speed last...always. Aside from focus, it is what contributes the most to a sharp image, and this is often a terribly overlooked fact.

 

If you are paying attention, and resetting your camera every time the light changes, you won't have to worry what to sacrifice, because you will have already made most the decisions, and just have to focus. If I use any auto setting (about 2.5% of the time), it will be as I am driving, and it is shutter priority, and usually if I am that strapped for time, I will just pick ISO 800 or 1600 to cover myself shutter and focus wise. In those situations, I know I am not going to get the sharpest shot anyhow. Usually the only time I will use an auto exposure setting is when I am not even looking through the viewfinder to shoot. I say this not to brag, but to make the point that they usually mess up your pix more than they help them. You are far better off thinking in advance than using an auto mode...but if you do, my preference has already been mentioned.

 

Keith

[nail33]

To William W (Retired):

 

Thanks for coming back to my post. I was worried that you would be upset with me for having posed the first question so poorly, as you spent so much time with your response. I am glad that I was a little bit clearer the second time around. I really like your suggestion in your second post. I also play the piano and your analogy to it was perfect. The more one practices, the less one has to look at the keys. I will try to set the camera in advance so I can easily go up or down 1 or 2 stops with Av and Tv giving me a quick 4 stop range and bump the Iso if need be. I will also practice being able to work the critical buttons without having to leave the viewfinder. Great advice. Thanks again.

 

To Keith Lubow:

 

I will try to set the camera in advance as the lighting situation changes so I will be closer to an ideal setting for those quick shots when they arise. Thanks

[William Michael]

>>> I was worried that you would be upset <<<

 

Don`t worry: to get me to UPSET status, takes a quite lot!

 

 

***

 

 

>>> I also play the piano <<<

 

 

Thank you for the compliment: at least you believe I can PLAY!

 

The piano is a much more frustrating tool than a camera, for me at least.

 

Regards,

 

WW

[bob_osullivan]

"ISO goes first, just as it did with film"

 

I have to dissagree. You have some very good lenses here. One of the features is good performance wide open.

 

I would go full wide open aperture before getting into very high ISO's (again, assuming no tripod so shutter speed is most important).

 

So, maybe Up ISO to 400 first, then max out aperture, then max ISO to 1600 or 3200 and laslty brace yourself and use a too slow shutter speed, but it should rarely come to that.

 

FYI, you 50 1.4 will be extreamly sharp and fine at F1.8 and above with sweet spot probably 2.8 and 4.

[William Michael]

>>> "ISO goes first, just as it did with film"

 

 

I have to [disagree]. (BO`S)

 

 

 

Bob, I am not sure we are in disagreement.

 

 

You have quoted my header sentence and not interpreted it in the context of my detailed explanation which followed (which also included a `thinking` four stop variance not dependent upon ISO): it is after that point I would normally ratchet the ISO.

 

 

But the question clearly was asking about that shot requiring instant response, `without thinking`.

 

I cannot see that there is that much difference between my overall procedure (ISO first; then Aperture; then Shutter Speed) and this procedure:

 

 

 

`So, maybe Up ISO to 400 first, then max out aperture, then max ISO to 1600 or 3200 and [lastly] brace yourself and use a too slow shutter speed, but it should rarely come to that.` (op cit)

 

 

 

Only in your description it describes a bit more time to think, and that I covered with:

 

 

 

`And, If I do not have time to think, I will sacrifice ISO right up to ISO3200, and if I had 6400 I would go there too.`

 

 

 

The key words being: `If I do not have time to think`.

 

 

 

So I agree entirely with:

 

 

`So, maybe Up ISO to 400 first, then max out aperture, then max ISO to 1600 or 3200 and [lastly] brace yourself and use a too slow shutter speed, but it should rarely come to that.` . . .

 

 

. . . if I had the time to think to do those three actions: if not, I would just ratchet the ISO that is much quicker, and no thinking, if practiced enough. That is all I was stating.

 

 

***

 

 

>>> FYI, you 50 1.4 will be [extremely] sharp and fine at F1.8 and above with sweet spot probably 2.8 and 4. <<<(BO`S)

 

 

Yes I agree and an important point too: I use it often at F1.8 through to F2.2: my passion is Available Low Light capture.

 

 

WW

[arie_vandervelden1]

A few thoughts.

 

- The rule-of-thumb that the sweet spot is at f/8-11 and/or 3-stops-down-from-max best applies to mediocre zoom lenses. Good zoom lenses and mediocre primes tend to have the sweet spot 2 stops down from max. Good primes and the best zooms tend to have their sweet spot about 1 stop down from max.

 

- To find out where the sweet spot of your lens is, try shooting a test chart. Have a close look to see how much difference there is between various f-stops, and keep this in mind when shooting.

 

- I have Tamron 90/2.8 and Canon 50/1.8. These are the closest I have to your Canon 100/2.8 and Canon 50/1.4. The Tamron 90/2.8 has a sweet spot at f/4-f/5.6, but wide-open it is still quite sharp. The Canon 50/1.8 also has a sweet spot at f/4-f/5.6, still quite sharp and useable at f/2.8, much less sharp at f/1.8-f/2.

 

- So, when shooting with the 90/2.8, if I want shallow dof I'll use f/2.8 without hesitation. But, for most intances I'll use f/4. If shutterspeeds are really high and there is no chance of shake, or if I want more dof, I'll stop down further. Similar situation for the 50/1.8.

 

- On the other hand, my old Tamron 28-300/2.8 was very mediocre at 28 mm. f/11 was definitely the sweet (least sour) spot. I'd shoot f/8 without too much hesitation, but f/3.5 (wide open) only in dire circumstances - better to up the iso instead.