hss

Enough with the megapixels and ISO!

What I want from the camera manufacturers

I was talking with Jared Platt and Jim Schmelzer after the classes I helped them with at Glazer's Camera's PhotoFest 2017 in Seattle today. After some technical discussions about high speed sync, hypersync, and old ASCOR strobes the conversation turned to camera features. Here are two, no make that three, changes we would like to see in ISO and megapixels. I have no idea if these are practical or feasible, but hey! Let's at least put it out there.

DROP THE ISO!!

The discussion of high speed sync led to our agreement that we don't need any more super high ISO settings. For portraits, especially outside with fill flash, we want LOW ISO settings. ISO 32, ISO 25, and even ISO 10 would be so welcome. Then we could more easily balance daylight exposures with fill flash and have some headroom to adjust shutter speed to control the ambient light levels without having the resort to high speed sync. High speed sync (HSS) is great. But it comes with a price--lower output power. Our lights have to be very close to our subjects with HSS. If we could go to a lower ISO we could keep the lights in regular sync mode and have the power available to back them up out of the frame or to use a larger light modifier with them. Right now the only way to do this with studio power level strobes that don't offer HSS is to use neutral density filters, and that has other complications, like difficulty focusing and dealing with color shifts from ND filters that aren't quite neutral. Are lower ISO settings too much to ask for?

If you aren't familiar with what is sometimes called syncro-sun flash, it is basically using a flash unit to supply fill light on a sunny day to lessen the shadows on your subject. You take an ambient light reading without the flash (let's say that is 1/60 at f/22 at ISO 100) and then you set your flash power to give an appropriate amount of light to open up the shadows. I picked the 1/60 shutter speed so that I have some headroom in case I want to vary the shutter speed to darken the ambient light exposure vs the flash. So, I could go as far as 1/200 to darken the ambient by 1 and 2/3 stops. But I am at f/22 and would much rather be somewhere around f/4 to lessen the depth of field and make the background less distracting. F/22 to f/4 is 5 stops. I could use a 5-stop neutral density filter on the lens to bring down the ambient light level to allow the f/4 aperture. 5 stops is a lot of light being cut out. It is going to give you a very dark viewfinder for composing and focusing. And it might be too dark for autofocus to work.

If, however, ISO 12 was available, the ambient exposure would be 1/60 at f/8 (3 stops different) and then only a 2 stop ND filter would be needed to get the exposure to f/4. Much easier to look through the viewfinder to compose and focus.

Enough with the megapixels!!

How many of us need more than about 20 - 24 megapixels? What if a camera manufacturer took a high megapixel sensor and used some of the pixels to extend dynamic range?

There are lens arrays that let you adjust focus after making the photo (see plenopticsa). And think of the Bayer filter array currently used to create color images. You have a red, a blue, and 2 green pixels that are used to create our color images. What if someone made an array of pixels that, in addition to color, produced an output of a dark, normal, and bright pixels that could be combined to create a kind of high dynamic range image without having to resort to combining multiple images in post processing? All the information would be in one file, so no worry about any movement during the bracketing sequence.

ISO Bracketing

Normally, we would bracket by taking a series of images in quick succession changing the f/stop (which changes the depth of field, which might affect alignment of the multiple images) or by changing the shutter speed (which changes the ability to stop motion, affecting alignment, and which won't work with flash exposures) on each of the images in the bracket. A third bracketing option is to bracket the ISO, but that usually requires additional equipment, like the CamRanger until camera manufacturers get wise to the need for ISO bracketing and add that to their cameras. If the bracketing could be done within one image you wouldn't have to worry about the change in depth of field or about subject movement between images. OK, so that's three things I want from the camera manufacturers, not two.

I haven't upgraded my Canon 5D MkIII or 6D bodies to newer higher megapixel models like the 5D MkIV or 5DSR. I don't need more megapixels. But if a new camera was introduced with better dynamic range and lower ISO settings, I'd be looking hard at purchasing the new model.

How about you? Do you see the benefits of lower ISO (they don't have to remove the higher ISO settings, those can stay, too), better dynamic range, or ISO bracketing? Please comment below.

 

Understanding High Speed Sync

It isn't about stopping motion

A few days ago I was having a conversation with another photographer and they brought up the idea of using high speed sync flash to stop motion. If I remember correctly, it was in regards to photographing liquid pouring out of a bottle into a glass. That got me thinking that the concept of hight speed sync (HSS) sounds like it might help, but that really isn't true.

Let's start with what HSS is. It allows you to sync your flash with shutter speeds above your normal sync speed so that you can use larger apertures for shallower depth of field or so that you can control the exposure on your background when working outdoors in full sunlight. A big minus is that HSS eats a lot of power and lowers the output of the flash and it eats through batteries (not an issue if you have an a/c powered flash).

What HSS does not do it help freeze motion. The two things that can help freeze motion are a fast shutter speed and/or a flash with a very short flash duration. High speed sync does let you use a faster shutter speed. But you no longer have a single fast flash burst. Instead, when your flash is in HSS mode it fires a number of times in rapid succession in sync with your camera’s shutter. The flashes are too close together for your eye to register them separately, so to your eye it looks like one flash, but it is actually strobing. At full power your speed light might take 1 to 3 or more seconds to recycle between flashes. In order to flash that many times in the short timespan of your shutter speed the flashes are relatively weak to allow the immediate recycling of the flash. 

To show this, I’ve set up a couple of very basic experiments with a speed light and a Paul C. Buff Einstein studio flash (which offers an “action” mode with a very fast flash duration). Nothing very fancy, it is just an ordinary personal size desk fan, a camera, and a light. As a control, the first image is taken without any flash. It is lit by window light with the ISO cranked way up (256,000) to allow for a shutter speed of 1/4000 second. You can clearly see that 1/4000 of a second was not fast enough to freeze the blades on the fan.

Next is a series of images lit by a Canon 430 EXII speed light, off camera, connected by a remote cable. The first two images are taken at 1/5 of a second and 1/200 of a second (normal sync mode) and you can see that the flash did a fairly decent job of freezing the blades of the fan, but not quite good enough to make the label on one of the blades readable. 

The next image is at 1/400 second, putting the flash into high speed sync mode. As you can see, it did a much worse job at freezing the blades of the fan. The next image moves the shutter speed up to 1/1250 of a second in HSS mode, and still a big blur. Even at 1/4000 of a second in HSS mode the label is a blur.

Compare the images at 1/4000 of a second with and without flash.

Very little difference in stopping action with or without a flash at 1/4000 of a second.

Very little difference in stopping action with or without a flash at 1/4000 of a second.

Now switch to the Einstein flash. The first two images have the Einstein in “color” mode which is intended to provide consistent color between flashes at the expense of a longer flash duration. You can see that at 1/2 second and at 1/160 of a second the label on the fan blade is not readily readable. 

Changing the Einstein to “Action” mode to provide a shorter flash duration gives us the last two images, made at 1/2 and 1/160 second. Even these have a blurred label, but much sharper than the images made with high speed sync at 1/4000 of a second. 

Now, I’m sure that most of us don’t have much occasion to photograph spinning fans. But we do sometimes get called on to photograph a liquid being poured. Does HSS help in this situation? I hope that you have already guessed the answer based on what you have read here so far. But let’s look at some images.

This time I will start with two using the Einstein. Each of these is at 1/2 second in “color” mode and in “action” mode. Both do a decent job of freezing the action of the pour and the bubbles.

Compare the above to the following images made with a speed light. The first one is at 1/60th second (normal sync) with good motion stopping. Next is at 1/500th second and we see that it is underexposed by a stop or two. Even with the flash being about 18-inches from the glass, it doesn’t have enough power to give me f/11. So, for the next image I bumped the ISO up from 100 to 400 to get a better exposure. Note that the action stopping is pretty much the same as at 1/60th of a second, at the cost of more noise due to the higher ISO (or you could give up depth of field and use a wider aperture—another tradeoff). Next I go to 1/2000 of a second, losing more power, but not gaining much, if anything, in the ability to stop action. 

Here are two pour photos side by side. One is lit with a speed light in high speed sync mode at a shutter speed of 1/2000th of a second. The other is lit by an Einstein flash in normal sync mode at 1/60th of a second. Can you see much difference in them? Can you tell which one is at 1/2000th of a second?

One of these pours is lit with a flash in normal sync at 1/60 of a second. The other is lit with a flash in High Speed Sync mode at 1/2000 of a second. Can you tell which is which?

One of these pours is lit with a flash in normal sync at 1/60 of a second. The other is lit with a flash in High Speed Sync mode at 1/2000 of a second. Can you tell which is which?

So, there you have it. High Speed Sync is not helping you freeze motion. It is mainly used for outdoor photos where you want fill flash at wide open apertures for limited depth of field and/or to control the ambient exposure. For example, let's say your are making a portrait outdoors and you want to use an aperture of f/2.8 and on that particular day the shutter speed would need to be 1/2000. Without HSS or the use of neutral density filters you can't use your flash to fill in shadows. You would have to lower your shutter speed to 1/200 to sync, and that would need an aperture of f/9 (3-1/3 stops difference). Using HSS would allow you to photograph at 1/2000 @ f/2.8 and use your flash (in pretty close to the subject, as it won't be a very powerful flash). It will also allow you to go to 1/4000 @ f/2.8 to darken the ambient exposure while still giving the subject the correct flash exposure.

What about HSS in the studio. Is HSS valuable in a studio situation? That depends on the lights you are using. Personally, I can’t think of a reason to use HSS indoors with speed lights. In ETTL mode you can set the aperture you want and a low ISO to be able to take photos at wide open apertures. With more powerful studio flash units it will depend on how low you can set the power on the flashes. If you find yourself with your flash at minimum power and it is still giving you a smaller aperture than you want, then you can  go into HSS mode and set your shutter speed above 1/250 and this will lower the power of the flash. Again, this is to control exposure, not to stop motion.

I hope this helps clarify things a bit. And, by the way, in the last image, A is 1/2000th of a second, B is 1/60th of a second.


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John Cornicello