I wanted to talk about magnification when reversing lenses and show you difference between 28mm and 70mm. It's a huge difference but every one of them have disadvantages and advantages. I will tell you from my experience what are disadvantages and advantages of every single focal length. I uploaded full resolution images for you to see how it looks when you zoom 100%.
Here is the photo I took few minutes ago, at around 35mm, because this lens have zoom feature that is perfect for macro photography. Why? Because by changing focal length with reversed lens you are getting better magnification but, from my perspective, details stays the same, only depth of field is changing.
| Camera | Lens | Shutter speed | F-stop | ISO |
|---|---|---|---|---|
| Canon 600D | Sigma 28-70 @35 | 1/80 sec. | f/8 | 200 |
Here are two photos of same subject with different focal length. You can see that 70mm reversed got much closer and you can see every single eye, or whatever it is called :D. But one disadvantage of this is too much magnification, you can't see environment, where they were at curtain situation. Sometimes that doesn't matter, when photographer wanted to show just a details of subject that almost fill full frame of photo.
| Camera | Lens | Shutter speed | F-stop | ISO |
|---|---|---|---|---|
| Canon 600D | Sigma 28-70 @70 | 1/200 sec. | f/8 | 200 |
Here is same subject, different location. At 28mm you get much better depth of field and you can see full size of this fly. Only disadvantage is magnification again, it's a lot lower than at 70mm but advantage is that you can see whole fly. As I said, depends of what are you want in your photo. With this Sigma that I have is great versatility, you can get close to subjects and far away from them.
| Camera | Lens | Shutter speed | F-stop | ISO |
|---|---|---|---|---|
| Canon 600D | Makinon 28mm | 1/125 sec. | f/8 | 100 |
Same on these two photos, I don't think it's same subject but you can see difference in magnification and depth of field. By closing aperture to your lens you need to think about lighting, so artificial lighting will be great so you can have clear and sharp image. Without it, you would probably have much noisier image because you need to raise shutter speed and ISO. With external flash you can freeze your subject even with slower shutter speed and lover ISO.
| Camera | Lens | Shutter speed | F-stop | ISO |
|---|---|---|---|---|
| Canon 600D | Makinon 28mm | 1/50 sec. | f/8 | 100 |
You can raise ISO a little bit but not too much, for example, for my Canon 600D the higher ISO without noise is around 200, it's an old camera with bad image sensor when you compare it with newer ones. But with external flash you can make great photos even with a older body, that cost maybe even 100$.
| Camera | Lens | Shutter speed | F-stop | ISO |
|---|---|---|---|---|
| Canon 600D | Sigma 28-70 @70 | 1/200 sec. | f/8 | 200 |
And one thing to remember is, you don't need expensive equipment to capture great details of macro photos, you just need more time and patience! Not every photo will came great, you need to take 20-30 or more photos to get the right one, I'm talking from experience. Without persistence there will not be great photos! Be persistent!