Focal length for product photography - 9mm or 90mm?

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Tim
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Just to set the scene I take shots of ceramic tableware in a tent or on worktops with two or three 100 Watt continuous lights. I'm restricted with lighting because I don't have the space for flash lights with soft boxes. This is our own product, I'm not a professional photographer by any stretch of the imagination!

For many years I used a Nikon E5700 for product photography and it produced very crisp results - the whole product was always in focus.

The only frustration I had was not being able to see the images properly until I ripped them from the memory card so last year I upgraded to a Canon EOS 70D with 18-55mm lens in order to get Live Preview shooting on a connected laptop but the Canon's narrow depth of field drove me nuts. Even on a mug it might get the front of the rim in focus but the back would be blurry.

I've got round this by using an aperture of f16+ but it has been bugging me. A great deal of what I read has been pushing me to buy a 90mm lens but last night I sat down and compared the image properties of the Nikon with the Canon (when Aperture is set to auto). After many comparisons I found both cameras produced images with very similar properties (Exposure time, ISO, Metering Mode, etc). The only major difference was Focal length.

The Nikon's constant focal length was 9mm. The Cannon varied from 18-55mm as expected because I've tried close ups and moving the camera further away and then zooming in.

I also have a Panasonic HC-V720 for filming but I tried a few product shots with this and it gives excellent depth of field. Literally everything in focus with f/1.8 and a focal length of 3mm. However its not the silver bullet because it struggles in low light and there is not much you can do with the shutter speed.

What I'd like to understand is if I'm really better off with a 9mm lens like my old Nikon which had such a good depth of field and if so why is 90mm+ pushed so regularly for product photography? Many thanks in advance for anyone who can enlighten me!
 
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Steve
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Your Nikon had a much smaller sensor (8.8 x 6.6 mm) than the Canon (22.5 x 15mm) , hence the 9mm focal length being recorded by the Nikon. If you apply a crop factor ( difference in diagonal sensor size between the two sensors) you will end up with the 'equivalent' focal length for your Canon.

Looking at the sensor sizes, the Canon sensor is approximately 3.9x larger so the equivalent focal length is somewhere around 35mm. That is, if you set your Canon to 35mm, you should see a similar framing to what you get on the Nikon from the same distance.

Another side effect of small sensors is their depth of field is considerably larger than that on a DSLR. This is shown by the amount of your subject that is in focus. As you've already done, the only ways around this effect is to stop down your aperture (meaning a large depth of field but requiring more light) or layer multiple images taken at different focus points (stacking).
 
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doodledsnaps
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Tim
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Thanks stevelmx5. Didn't realise the sensor size played such an important role so really I've probably bought the wrong camera for my needs when I "upgraded".

We've been thinking about changing it anyway because its pretty bulky for holidays, weekend trips etc. but I looked at the Canon Powershot range and noticed that although they give the mm sensor size for their DSLR cameras they don't for Powershot - instead they start talking in mega pixels. Is there a reason for that and how can you actually compare the two?
 
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Ned
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Thanks stevelmx5. Didn't realise the sensor size played such an important role so really I've probably bought the wrong camera for my needs when I "upgraded".

We've been thinking about changing it anyway because its pretty bulky for holidays, weekend trips etc. but I looked at the Canon Powershot range and noticed that although they give the mm sensor size for their DSLR cameras they don't for Powershot - instead they start talking in mega pixels. Is there a reason for that and how can you actually compare the two?
The simplest thing to do is to just look for the sensor size and the rest will follow as pretty much any camera with kit lens will cover a similar range of effective focal lengths. If you just want to buy something that will 'work' modern compact cameras with a 1" sensor (which are actually nothing like 1" but that's a different story) offer a great mix of larger DoF and image quality so you could look for one of those.

Alternatively you could be looking to understand the techniques that product photography uses, such as LIGHTING and high f-stop, focus stacking and probably a number of alternatives that I am unaware of. I say lighting in caps as that is the real key to good photography, not the camera - pretty much any camera will do if you know what you are doing.

90mm is often cited as a good product photography focal length as it offers a flattering perspective without accentuating any depth or feature of the product, this GIF illustrates it well: http://jnack.com/blog/2016/03/13/a-great-photographic-gif-how-focal-length-affects-a-portrait/
 
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doodledsnaps
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Thanks Nawty. I know what you mean about lighting but space for a proper set up is one of my limitations. As we only need the images for the web and A4 catalogue type content (no billboards, etc) fiddling with shutter speed and aperture gives us the results we want. But if we can get the results we want with a much simpler camera and one that is easier to carry for everyday snaps then the 70D we bought is probably over cooking the turkey!

When I did my research Live Preview shooting was essential alongside better resolution and we thought it was time for a 'proper' camera (proper lens, etc) but every time we want to take a shot we have to reach for the user manual just to get a point and click result. Under qualified owners I think!
 
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Terry
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Back in the 50's and 60's the weapon of choice for product photography was large format of 5x4 or larger.
There have always been problems with depth of field in product photography. When shooting hollow ware and the like, apertures of F 45 or beyond were the norm.

It is true that diffraction kicks in long before that, but depth of field in these situations is more important than ultimate sharpness. It will certainly look sharp.

The possibility of using multiple shots has eased the situation today, as the software for focus stacking is very easy to use. Though it is perhaps necessary to get a focus rail to make the steps rather than changing the focus with small objects. Like most techniques it is a matter of getting in to a routine, and it then all becomes very simple.
 
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Dave
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Thanks Nawty. I know what you mean about lighting but space for a proper set up is one of my limitations. As we only need the images for the web and A4 catalogue type content (no billboards, etc) fiddling with shutter speed and aperture gives us the results we want. But if we can get the results we want with a much simpler camera and one that is easier to carry for everyday snaps then the 70D we bought is probably over cooking the turkey!

When I did my research Live Preview shooting was essential alongside better resolution and we thought it was time for a 'proper' camera (proper lens, etc) but every time we want to take a shot we have to reach for the user manual just to get a point and click result. Under qualified owners I think!
A couple of things. To increase the DOF just move the camera back a bit. The further the camera is from the subject the more you will have in focus. Dont try and fill the frame with the image. You also have a DOF preview button on the camera. This stops the lens down so you can actually see what the DOF will be like in the finished shot. You will notice things get very dark when you do this, but it should help and doesn't effect the actual shot taken.
 

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doodledsnaps
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Tim
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Thanks for all the feedback. I have tried moving the camera further away and it works to some degree but its just another flaff. Ultimately I want a camera that I can connect to a laptop for live view and see the picture I want rather than trying to imagine the cut out bit. I did find the DOF button a couple of months back and that has helped (but thanks for the pointer, it is not at all obvious!). However I still think that rather than try and make this camera work for me by fiddling around I would be better off with one that has a smaller sensor which would just make things more straightforward.
 
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