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JimC Mar 21, 2010 3:02 PM


Originally Posted by elizberd (Post 1068287)
For now I have a big question: I'm not understanding why I'll have shallower depth of field with a dslr than with my g6. Depth of field and camera shake is already an issue.

Your G6 has a very tiny sensor in comparison to the larger APS-C sensor used in the dSLR models you're looking at.

As a result, you can use a much shorter "actual" focal length lens for the same subject framing at a given focus distance. The lens on your G6 is a 7.2-28.8mm lens. But, because of how small the camera's sensor is, you have the same angle of view that you'd normally have using a 35-140mm lens on a 35mm camera. But, Depth of Field is going to be based on your actual focal length (not your 35mm equivalent focal length), focus distance and aperture. So, since you'll need to use a much longer actual focal length lens for the same subject framing at a given focus distance with a dSLR model, you'll have a much shallower depth of field for a given aperture setting.

For example, your second photo was taken at an actual focal length of 28.8mm (giving you the same angle of view you'd have using a 140mm lens on a 35mm camera), but with a lot more depth of field than you'd have using a 140mm lens on a 35mm camera at a given aperture setting. The greater depth of field you have with a camera like your G6 using a smaller sensor, is one reason it's so difficult to blur the background with a larger subject (i.e., your people type photos). You tend to have too much depth of field to make doing that very practical. That's one reason many users prefer to use a dSLR model with a larger sensor size (so that they can open up their aperture to help isolate their subjects from distracting backgrounds). But, for macros, you usually want more depth of field. ;-)

The smaller the sensor or film size, the narrower the angle of view for a given focal length lens. The larger the sensor or film size, the wider the angle of view for a given focal length lens. The smaller the sensor or film size, the greater your depth of field for a given subject framing and aperture. The larger the sensor or film size, the shallower your depth of field will be for a given subject framing and aperture.

So, you need to use a much smaller aperture (higher f/stop number) with a dSLR model for the same depth of field for a given subject framing as compared to your G6.

A camera like the Nikon D5000 you're looking at is using a Sony APS-C size sensor. That's not as large as 35mm film. But, it's a lot larger than the sensor in your G6. Basically, a 90mm lens (like the Tamron 90mm Macro I'm talking about), would give you the same angle of view you'd have using a 135mm focal length on a 35mm camera. I used an APS-C size sensor with a 90mm actual focal length to compute the depth of field I gave you in my previous post. It can be very shallow at focus distances that close when you're trying to fill the frame with a subject that small (1.5" painting).

This Depth of Field calculator may help:

If you pick a camera model and enter in the actual focus distance, actual focal length (not 35mm equivalent focal length) and the aperture you want to shoot at, it will compute depth of field for you.

You're probably going to need to be about 12 inches away (from the sensor/film plane, not the end of the lens), to fill the frame with a 1.5" painting using something like a 90mm Macro lens on a camera using an APS-C size sensor (like the Nikon D5000). Your Depth of Field is going to be quite shallow at a focus distance that close, making hand holding a camera very difficult if you want accurate focus, even if you do stop down the aperture some from wide open. Note that you'd need to use around 28mm for the focal length with your G6 for the same framing at the same 12 inches away.

When you do stop down the aperture, then slower shutter speeds are needed for proper exposure.

The aperture scale (in one stop increments) goes f/1.0, f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/11, f/16, f/22, etc. With each one stop move to a smaller aperture (represented by a higher f/stop numbers), you will need shutter speeds twice as long for proper exposure at the same ISO speed and lighting level. For example, if you go from f/2.8 to f/4, you'll need shutter speeds twice as long for the same lighting and ISO speed.

So, trying to fill the frame with a subject that small with a hand held camera indoors in artificial lighting is going to be very difficult, because of the potential for focus error due to a very shallow depth of field, and/or blur from camera shake if you try to stop down the aperture for greater depth of field (because slower shutter speeds will be needed).

Now, on the plus side, you can get away with much higher ISO speeds using a dSLR model to offset it's shallower depth of field. But, if you're already having trouble with your G6 in that area, I don't know how much improvement you can expect trying to do the same thing with a dSLR if you can't use a tripod. ;-)

Perhaps I'm being overly cautious. But, I think you're underestimating the difficulty of getting sharp photos with a subject that small without a tripod in indoor lighting.

Now, stabilization may help some. IOW, you could try to use something like a Nikkor 85mm f/3.5 AF-S VR Micro (around $500), or a 105mm f/2.8 VR AF-S Micro lens (around $900). But, from what Thom Hogan (a very respected photographer and author) says in his review of the 105mm, VR (Vibration Reduction) performance doesn't work well at very close ranges:

I have seen some evidence that body based anti-shake may still be effective at very close ranges. For example, see this hand held image from a KM Maxxum 7D owner using a Minolta 50mm lens at f/4 and 1/10 second.

Note that the sensor shift based stabilization used in the Sony models is a more refined implementation of the Anti-Shake System used in the Konica Minolta models (same basic system design with better algorithms, since Sony bought Konica Minolta's camera related assets and improved it in newer generations). But, without controlled conditions testing, that's only speculation (IOW, that may have been a lucky shot). Also, it may not have looked that sharp when enlarged more (and I still don't understand what you want to do with the images you take of the paintings).

Note that with a Sony dSLR, a lens like the Tamron I'm referring to would still enjoy the benefits of stabilization (since it's body based in the Sony models and all lenses you use would benefit from it).

But, for macros, a tripod is still a better bet (and then you wouldn't need to worry about having stabilization to help out; and could use lower ISO speeds for better image quality, stopping down the aperture as desired.

Now, if you don't need to "fill the frame" with a subject that small, and can shoot from a bit further away and crop later, that will help with depth of field. That could also eliminate the need for a dedicated 1:1 Macro lens (you'd need a 1:1 Macro lens to fill the frame with something as small as a 1.5" painting). It all depends on what you want to do with the images. I'm still unclear about whether your intent is to enlarge them later (much larger than their actual 1.5" size) or not. If not, you could probably shoot from a little further away and crop them a bit.

JimC Mar 21, 2010 3:50 PM

IOW, I'd let members know what you plan on doing with the images for a better idea of how to approach it, giving desired print sizes if you plan on enlarging them later.

I sort of doubt they're going to have a lot of "real" detail if you enlarge them that much anyway, due to the difficulty of painting something that small, depending on what you're trying to show (i.e., every ripple of paint texture or not). Shooting from further away and cropping some later may let you use a less expensive lens and give you a bit more depth of field to help out with focus error (and if you're not enlarging them a lot, then any image degradation from noise and noise reduction won't be as noticeable either).

peripatetic Mar 21, 2010 3:52 PM

You definitely need a tripod.

You definitely need a Live View camera (don't need the Sony, any one will do) and switch to high-magnification and manual focus and ideally with a good Macro lens. The ability to switch to high-magnification here for fine-tuning on manual focus is much more important than AF speed.

There are lots of cameras that will work for you:
Sony A550 or similar with 90mm Macro and kit lens.
Canon 550D or similar with 100mm Macro lens and kit lens.
Nikon D5000 or better with 100mm Macro lens and kit lens.
Olympus E-series or E-P series with kit lens and Macro lens.
Panasonic G-series or GF with kit and Macro.

And a good tripod (NOT a cheap one. Ideally $300+)

Ideally you will also get some kind of Tungstgen soft light and stand. ($200 starting.)

JimC Mar 21, 2010 4:55 PM

peripatetic has the right idea if you want maximum detail, and like he says, you'll want to use manual focus anyway filling the frame that much with a smaller subject. In that type of situation, a magnified Live View image (using a camera's main imaging sensor) is a better way to go, because you will have a very shallow depth of field and AF can't cope well with that type of subject.

A Live View system like the Sony's ability to use a separate Live View sensor in the viewfinder housing offers no benefit for that type of subject, and using it's separate Live View sensor is probably not a desired way to approach that type of subject anyway. Fortunately, the A500 and A550 do have the ability to use the camera's main sensor, too (using what Sony calls Manual Focus Check Live View mode), which uses the main imaging sensor and gives you the ability to magnify the image up to 14x.

Models from other manufacturers with Live View have the same type of feature, allowing you to magnify your focus point to help out with focus accuracy. That's what peripatetic is referring to. For example, the Nikon D5000 gives you that ability since you seem to be leaning in that direction and like it's articulating LCD design.

Is there a reason you can't use a tripod?

If you want to capture the best possible detail, that's the way you'd want to approach it, just as he described (very steady tripod, manual focus using a magnified live view, good quality macro lens). You wouldn't won't stablization either (you'll want to turn it off when using a tripod if you're using a system or lens that has it).

Chato Mar 21, 2010 5:02 PM

Personally I think the Sigma DP2 is ideal for this situation. You can mount it on a tripod, use the LCD for manual focusing. It's color reproduction is extremely accurate, and it's DOF is easily set.

It's built in flash is useless, but then again, the built in flash of most cameras are useless. You can either buy an optional flash to mount on the hot shoe, or slave a flash to the camera. The macro mode only goes down to one foot, but I really don't see the need for such a mode when you're shooting paintings.


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