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Hi Guys,

We are photographing chronic ugly wounds for a study and cant get the shot right. We dont get everything in focus.

We have a 100 mm prime macro lens but cant get a good DOF when the lens is wide open under no flash.

Does the 20D do fill fash on aperture priority? If so how? It works great under program mode but with a very shallow DOF.

Any help will be appreciated since we have to advance the study with nice photos.

Hi

Use higher ISO e.g. 800 or 1600. You need f8 - 16 for DOF. If you can't use flash, use table lamps or anything of light. You need lots of light to get clarity and sharpness.

regards,

Arthur

thanks yeocsa, I'll give it a try on the next patient. Hopefully they dont thinks its odd shinning a beam of light on their legs for a photograph

Hi

You are welcome. If possible, use a tripod. In macro, the slightest movement even e.g. cause by mirror can cause camera shake.

Use the custom setting for mirror lockup. First press of shutter, swing up the mirror. Second press of the shutter, takes the picture.

regards,

Arthur

have also seen a ring flash used in medical work.

Steve

Keep it simple! A tungsten lamp...ISO 400 and 1/30th at the smallest f-stop you can get away with whilst getting accurate exposure. Do a WB pre-set.

hi steve, we are using the ring flash without success.
I'll try both what matt and arthur suggested. Thanks

Nito - dentists, doctors and other medical professionals have used the 200mm Nikkor along with ring flash for many years with great success. Notice that I said the 200mm Nikkor, you need distance, but in having said that, the 100mm should be fine.

I used this kind of equipment prior to digital and it was often hit and miss. With digital you do have the opportunity to view images immediately and know whether or not you have a good image.

The one thing to keep in mind is that the lens should be as parallel to the wound as possible. If using a ring flash with dual strobes you can increase the shadows by using only one of the strobes - sometimes necessary to indicate wound depth.

sirhc55, yes we are keeping the len parallel with the wounds with a size indicator on the size. In small consultantion rooms, the 100 mm len is not ideal but we can still get a decent shot off. The issue is light or lack of light for the shot. We need a quick photograph protocol that can be followed by the clinicians and nurses with no fuss for the clinical trial.

To all thanks for the help.

Nito - what ring flash have you used

nito wrote:sirhc55, yes we are keeping the len parallel with the wounds with a size indicator on the size. In small consultantion rooms, the 100 mm len is not ideal but we can still get a decent shot off. The issue is light or lack of light for the shot. We need a quick photograph protocol that can be followed by the clinicians and nurses with no fuss for the clinical trial.

To all thanks for the help.

Hi Nito,

A macro lens has a "flattening" effect. So using at least 1 light from the side can help bring out the "depth". Fill flash on the other hand tries to fill the shadows and thereby, reducing the "depth". That's why in macro, we always position the flash just above the lens (near the filter) and at 45 to 60 degrees towards the subject. We often opt for -2/3EV so as not to burn out the highlights.


Yes, do set the appropriate white balance depending on the light - tungsten or white light.

regards,

Arthur

The 20D does fill flash not problems. Turning custom function 3 to 'auto'. I also have my 550EX set to high speed sync most of the time but that shouldn't be a problem as it sounds like you will be less than 1/250th sec anyway.

In Av-priority the camera will set the shutter speed based on the ambient metering. If flash is your main light this probably isn't what you want.

Try manual, with the shutter speed set to a nominal value. Above 1/250s you'll lose flash power, and the slower you go the more ambient light will register (but the more you'll have to worry about camera/subject movement). If there's no ambient light to speak of (i.e. flash is your only effective light) you could use 1/250s with no problems. Set the aperture to a reasonably small opening (ie. high f-stop) to get as much in focus as possible.

The flash lighting will be metered using E-TTL (ambient or evaluative depending on C.Fn.14) so you can just adjust the exposure using the flash exposure compensation.