Trogon Photo Tours

July 2011 Newsletter

This newsletter discusses how to choose which iso you should use when doing bird photography. 
 
The biggest impetus for me changing from shooting slide film to digital about 6 years ago was that I saw that photographers were routinely shooting at iso 400 while with film photography I was shooting at film speeds of 100 or 200 and at 200 the images were quite grainy.  I realized that for action photography and getting a faster shutter speed, digital would be the way to go.  So how did I determine which iso I would use when I started shooting digital?

The lower the iso that you use generally the less noise you will have and the higher quality image you will get.  However the higher iso that you use means that you will be able to use a faster shutter speed and/or more depth of field to get your image. Shutter speed is critical for stopping the action and helpful for sharpness.  Capturing multiple subjects often means using a wide depth of field.  Understanding this trade off between image quality (lack of noise) and ability to stop the action and use more depth of field is paramount in deciding which iso you will use.

Which iso you choose will depend on 1) Which camera you are using? 2)  What you are trying for in the
photograph? 3) How will you use the photograph? 4) What are your lighting conditions for the shot?

HARRIS'S HAWK photographed November 2009 at Sweetwater Wetlands, Tucson, Arizona.  Canon 1D Mark III, 500mm F4 lens, 1/1600 at F6.3, iso 640, Aperture priority, evaluative metering -0.3.  I just clipped the toenail of the left talon in this shot so I added a bit of canvas at the bottom.  When photographing at Sweetwater Wetlands we came across a group of young Harris's Hawks.  There were 2 young birds perched on a fence line in nice mid morning lighting.  How did I chose my iso for this shot?  It was a combination of all the factors listed above. 

The most important one being - what was I looking for in the shot?  With these young birds perched on a
fence line with plenty of lighting available I certainly could have been shooting this at quite a bit lower iso.  That would have meant that my image of the hawk on the fence line would have no or very little noise and if I wanted to I would be able to print it quite large.   However an image of a hawk sitting on a fence line is generally not a particularly compelling image and certainly not one that I'm going to end up printing large.  I am interested in capturing compelling action and behavior shots of birds, not static ones.  Therefore I was set up with an iso here that allowed me to have a shutter speed that was fast enough to get good flight shots if the bird took off.  Well, sure enough the young hawks started taking off and I managed to get some nice images of them.  The camera I was using, the 1d Mark III shows a little noise but not much at iso 640 so I am still getting pretty good image quality.  At iso 200 and that F-stop I would have had a shutter speed of about 1/500 which wouldn't have been fast enough to stop the action here.  If I were the lucky the face might still be sharp but that would be about all.  I felt that with a large bird like this and being close to it I needed to stop down at least 1 stop to make sure the head was sharp when the bird took off. 

This is how I usually select my iso - I pick an iso that gives me enough shutter speed to stop the action if
action occurs.  Note that I'm prepared for action to occur at all times then.  If you have a low iso and shutter speed you won't have time to change any settings if the bird takes off.  However I also take account of which camera I'm using and how it handles noise. 

BLUE PITTA photographed January 2009 at Phu Khieo Wildlife Sanctuary, Thailand.  Canon 1D Mark III, 500mmF4 lens 1/25 at F5.6, iso 1000, evaluative metering -0.3, 580ex fill flash at -1.0, Gitzo tripod, blind.  When I'm photographing in the forest there's not enough light to stop the action.  In fact I'm sometimes struggling to just get enough light to make a good static image.  That was the case here.  Iso 1000 is about the highest the 1D Mark III can go without producing significant noise.  Mixing some fill flash with the ambient light I was able to get a shutter speed of 1/25 at iso 1000 while stopping down 1 stop.  1/25 is about the minimum shutter speed that I can consistently make sharp images of birds that aren't moving if I'm using a sturdy tripod.  I wanted to stop down 1 stop to get the whole bird in focus as well as the right leg. 

I said previously that which camera body you are using will partially determine what iso you will want to use.  The Nikon D3s is rated by www.dxomark.com as having good low light iso performance up to 3200 iso while the Nikon D300 is rated as having good iso performance up to only iso 640.  DxoMark tests camera bodies for color depth, dynamic range and low-light iso performance.  It then gives the cameras an overall score.  However what we are particularly concerned about in this article and often in wildlife photography is low light iso performance.    On the dxomark index page you can select your
brand of camera (Nikon, Canon etc) under Camera image quality and ratings for:.  After selecting your brand you can select your particular model and see how your camera body rates overall and for low light iso performance.  It lists the maximum iso that each camera still retains a specific amount of image quality due to lack of noise and other attributes.  I have found that their scores are quite accurate for most of the bodies that I've tested.  For example it lists the 1D MarkIII as having an iso score of 1003.  I find in practice the image quality and noise is still acceptable at this level, there is a little noise but it's not overwhelming and is manageable.  In the case of the pitta I was challenged for light so I used the maximum iso that would get me good results.  What I've also found is that if you take the iso score by www.dxomark.com and divide it in half at that iso you get excellent results.  So for the Mark III that gives me an iso of 500 which is what I work with if there is lots of available light to achieve the image that I want.  I shoot most of my images with the Mark III at iso 500-640 which allows for some cropping as well.  (Cropping an image will generally increase the amount of noise).  However I now usually shoot with
the Canon 7D.  The 7D scores out at 854 for iso performance.  This means that 800 is generally the highest iso that will produce a good quality image at full frame.  Applying my 50% test which allows for cropping and gives excellent image quality gets me to iso 400 which is what I use with this camera when there is adequate light. 

You might ask "why are you using a camera (7D) that has a lower overall quality score and lower iso performance than your Mark III?"  The answer is that there are several things which are important to camera performance which aren't taken into account in the dxomark scores.  The amount of megapixels and particularly the autofocus performance of the 7D I find quite superior to that of the older 1D Mark III.  I also like the 1.6 crop factor of the 7D.    I am still waiting to see if Canon produces the equivalent of the Nikon D3/D3s and to see what Nikon ends up coming out with next. 

So you can see that how your camera handles noise is very important.  I had a workshop participant who shoots the Nikon D3 and before my workshop he had been taken most of his shots at iso 200.  This often limited the depth of field and shutter speed that he could use.  Because the D3 has great iso performance and is rated at over 2200 iso by dxomark he was under utilizing the abilities of his camera.  After pointing this out to him his photography took off and he started getting lots of
good flight and action shots.  He now routinely shoots this camera body at iso 800.  Based on the scoring he could go even higher for a default iso setting but oftentimes iso 800 that will give you plenty of room for shutter speed and depth of field.  On the other hand I have participants who use the D300 and they have to be much more careful about what iso they are using - I recommend 250 to 320 with that body if there is enough available light.  The same goes for the Canon 50D.  

HOATZIN photographed January 2010, Sani Lodge, Ecuador.  Canon 1D MarkIII 500mm 1/250 at F4, iso 1000, evaluative metering -0.3, handheld from canoe.  This is another situation where I took this image at what I thought the limit for getting a good quality image without too much noise.  I also went wide open with the F-stop just to get to 1/250.  This is a full frame image (in fact I wish I had a touch more room at the bottom) so cropping wasn't going to cause more noise and I was pleased with the result.  Most of the uses of my images are for my website and posting photos on various internet photography forums.  I also occasionally end up having images published in books.  For these uses noise is not as much of an issue as if I wanted to print this very large.  On the other hand I have entered
the Wildlife Photographer of the Year contest each year the past 2 years and if one of my images were selected as a winner or commended image the contest would end up printing it 6 feet long and displaying it.  So I certainly have an incentive to keep my iso down as well.  In the end the lighting and shooting conditions dictated the iso here.  Shooting from a canoe handheld I wasn't confident I would get a sharp image at lower than 1/250.  By the way this image made it to the semi-final round of judging of that contest in the animal portrait category and was a top 100 image in the annual Audubon Society Contest.

SNOW GEESE mating photographed at Bosque del Apache NWR, New Mexico, February 2009.  Canon 50D 500mmF4 1.4x teleconverter at 1/3200 F8, iso 400, evaluative metering -1.0, aperture priority, handheld.  I took this image about a month after purchasing the Canon 50D.  I had mistakenly thought that the camera would be a good iso performer at iso 400 while it is rated good up to 640 iso by www.dxomark.com in practice I found it was quite mediocre at iso 400.  While this image had a little bit of noise and the image quality is good not great I certainly had enough light in this situation to shoot this at a lower iso. If I had it to do over I would have shot it at iso 200 because 1/1600 still would have been plenty of shutter speed to stop this action and the image quality (lack of noise) would have been excellent as opposed to good.  I didn't end up using the 50D for very long because of it's poor iso performance.  However, my wife Angie likes it for photographing family so that's what it is used for now.

OSPREY with Bullhead Catfish photographed May 2011, Ankeny National Wildlife Refuge, Oregon.  Canon 7D 500mmF4 lens at 1/1000 F5, iso 800, manual exposure, handheld.  This was photographed on a dark, cloudy day at Ankeny Refuge recently.  I occasionally see photographers posting on internet forums that they only photograph when the lighting is good.  As a nature photographer you are going to pass up many great moments if that is the way you operate.  At Ankeny on this day Osprey were regularly hauling out catfish close to the viewing area.  I certainly wasn't going to pass up an opportunity to photograph this action.  I even ran into another photographer who was watching the action from his car and had his 500mm in the backseat but didn't get out to shoot because he thought the light was too poor.  Well needless to say I'm pretty happy with this image which I would consider entering in photo contests.  In terms of the iso selection 800 is about the maximum that will produce a good quality image with the 7D and even then is pushing it a bit but I needed to get at least 1/1000 to stop the action and since these are big birds I felt I needed to shoot not completely wide open so I went with F5.  If it was a lighter day I certainly would have preferred to shoot this at iso 400 which is my default iso for the 7D. 

So in conclusion I select the iso which I think I will need to have enough light to get the image that I'm after.  Oftentimes that's an action or flight shot.  However, I'm also keeping in mind the noise limitations of the camera body that I'm working with.  Understanding this trade off between how your camera handles noise and the settings needed to get the photo that you are after will help you select the appropriate iso.  Many cameras now have an auto iso capability.  I don't use auto iso because I prefer to always have control over my settings.  However even if you use auto iso this discussion is helpful because it will help you set the minimum and maximum isos that you would want to use with that function. 

If there is plenty of available light and you want to keep things simple, take the www.dxomark.com lowlight sports iso rating for your camera and divide it in half, then reduce it to the next available iso stop on your camera.  For example the Nikon D300 has a dxomark iso rating of 679.  Divided by 2 this gives you 340, the next iso stop down from that is iso 320.  This would be appropriate default iso for that camera if there is plenty of available light.  You should have pretty good noise performance and in good lighting be able to generate enough shutter speed to stop the action.  This is just a default for your average situation, if you are working from a tripod and going for a static shot in good light it may make sense to go down to iso 200, while if the lighting is low and you are handholding you may want to go up to iso 640 or so.  With cameras like the Nikon D3/D3s and D700 that have great iso performance I
think an appropriate default iso is 800.  This is less than half of their dxomark score but should give you plenty of shutter speed in most situations.  However remember that with those cameras you can certainly go higher if the conditions dictate it.