Macro photo exposure 700D

[mike21]

When taking a photo of an insect on a plant I wish to set aperture at around f18 and shutter speed at around 1/250 to freeze subject movement. This means setting to manual where I would then want to set to auto ISO, but auto ISO is greyed out in manual. Using trial and error to get the right ISO likely means the insect has flown before the picture can be taken. What is the recommended procedure to take this kind of picture.

[cicopo]

I don't do much macro but I'd use a wider aperture (for a few reasons) & a faster shutter speed. Going old school you pick an ISO that fits the light of the time of day allowing the settings that are relatively close & fine tune SS or Av when taking the shot. 

[MikeSowsun]

---

mike21 wrote:

When taking a photo of an insect on a plant I wish to set aperture at around f18 and shutter speed at around 1/250 to freeze subject movement. This means setting to manual where I would then want to set to auto ISO, but auto ISO is greyed out in manual. Using trial and error to get the right ISO likely means the insect has flown before the picture can be taken. What is the recommended procedure to take this kind of picture.

---

Auto ISO should not be greyed out in Manual mode.  Reset your camera back to default settings and see if you can access Auto ISO in Manual mode.

[kvbarkley]

My T6S uses Auto ISO in manual mode.

[diverhank]

---

@mike21 wrote:

When taking a photo of an insect on a plant I wish to set aperture at around f18 and shutter speed at around 1/250 to freeze subject movement. This means setting to manual where I would then want to set to auto ISO, but auto ISO is greyed out in manual. Using trial and error to get the right ISO likely means the insect has flown before the picture can be taken. What is the recommended procedure to take this kind of picture.

---

Auto ISO should not be greyed out in M mode.  The only thing you can't do in M is exposure compensation.

As a side note, I think f/18 is excessive...and it may not gain you very much depth of field and it will cost you a whole lot of ISO noise.  You should use one of these online depth of field calculators and see for yourself whether setting to f/18 would help you improve depth of field or not.  You should research focus stacking and use that instead to improve DOF.

[Waddizzle]

---

@mike21 wrote:

When taking a photo of an insect on a plant I wish to set aperture at around f18 and shutter speed at around 1/250 to freeze subject movement. This means setting to manual where I would then want to set to auto ISO, but auto ISO is greyed out in manual. Using trial and error to get the right ISO likely means the insect has flown before the picture can be taken. What is the recommended procedure to take this kind of picture.

---

What lens are you using?

I think f/18 is way too narrow for optimum resolution.  And, a 1/250 shutter speed is not exactly “fast”, either.  Most lenses get optimum performance at f/8.  I typically shoot at 1/800 to 1/1600.  Try backing away from the subject just a bit, and crop the image in pot, to get more depth of field.  You do not always have to shoot at MFD, minimum focus distance.

As others have noted, you should be able to set ISO to Auto in manual mode.  Your camera may have a “Safety Shift” feature, which overrides your ISO setting when your settings could result in a bad exposure.  With your aperture at f/18, you could be seeing “Safety Shift” kick in, which would override your manual ISO setting.  

If your camera has “Safety Shift”, then I would disable it.  Observe whether or not there is anything flashing in the viewfinder.  If something is flashing, then your exposure settings are not well adjusted.

[mike21]

Thanks. Auto ISO does work when I use a larger aperture and slower shutter speed, it seems that what I was trying to do was outside the range as my trials were attempted in dull winter light, in summer light it should be fine. I have had success photographing flies with a bridge camera but not with the dslr so far due to it's much larger sensor and hence much smaller depth of field. I will try moving futher away and cropping more but maybe flash is the answer. 

[Waddizzle]

This was shot with a T5 and the EF 100mm f/2.8L. The lens has an MFD of less than a foot, but I think I had backed of to around two feet, or maybe a bit more.

The crop is the center third of the photo.

[Waddizzle]

I have found this online calculator to be invaluable.

http://www.dofmaster.com/doftable.html

[TCampbell]

We're usually stuck thinking about "exposure" as the "exposure triangle" (shutter speed, focal ratio, & ISO gain ... although ISO gain isn't technically part of the "exposure").

But something else you can always do to help exposure is to bring more light to the shot.

A normal pop-up flash or shoe-mounted flash is often a problem for macro shots due to issues of having lens shadow in the shot at close subject distances.  But there are macro lights such as macro ring lights and macro twin lights.  

Canon's flashes aren't cheap.   I own a Canon MR-14EX II Ring LIght.  It's still around $500-550.  But you can get third party ring-lights for about $100.  

A twin-light is usually a bit more.   A Canon MT-26EX-RT is just shy of $1000, but it is more powerful and it lets you push the light farther to the sides to create a bit more 3D texure on your close-subjects so they don't appear as flat.  A 3rd party version of a twin-light would probably be closer to $200.

You can set the ratios ... with ring lights or twin lights ... they behave as if they are two flashes (left side vs. right side) so if you want to create some directionality to the light you can set one side to provide the key light and the other side to provide fill.

So here's the magic part... these are "TTL" (Through The Lens) automatic flashes.  (On Canon it's E-TTL II).  This means the flash actually fires twice in extreme rapid succession (so fast you'd swear it only flashed once).  In fact, 4 things happen when you take a shot with an E-TTL II flash.

#1 it meters the shot with no flash to determine how much available light exists.

#2 it fires the flash at very low power (typically 1/32nd power level) WHILE metering the shot again.

#3 It COMPARES the metering results of #1 and #2 to determine how much the flash helped the shot and uses this info to determine how much actual power should be used to take the shot.

#4 It sets the flash power to the computed power level (determined in step 3) and the camera takes the shot.

Again, this all happens so fast that you'd swear the flash just fired immediately and only once as soon as you hit the shutter button.

But you can still use manual exposure and this still works.  You can set the shutter speed to the camera's max flash-sync speed (for your camera that might be 1/250th) and you can set the aperture down to something like f/22.  This gives you a very broad depth of field.

You might be thinking 1/250th is too slow.   But at f/22 very little ambient light will enter the lens.  Nearly all of the light that contributes to the exposure will come from the flash.  And the flash is lit for substantially less than 1/250th sec.  It's probably only lit for maybe 1 or 2 thousandths of a second ... and that IS fast enough to freeze action.  

Using a macro flash (either ring-type or twin-light type) at f/22 and the fastest flash sync speed your camera allows will help you get these shots and "freezing" the action.

Here's a video